to any interest of man. If =toads= are encouraged to take up their
abode in a garden, they will aid in ridding it of insects. A house may
be made in a shady corner with four bricks, or better still, a hole a
foot deep may be dug to furnish them protection from the heat of the
day. A toad’s muzzle is not so tapering as a frog’s (why?), its feet
are not so fully webbed (why?), and its skin is not so smooth (why?).
In case of doubt open the mouth and rub the finger along the upper jaw;
a frog has sharp teeth, a toad none at all. The tadpoles of frogs,
toads, and salamanders are much alike. In toad’s spawn the eggs lie in
strings inclosed in jelly; frogs spawn is in masses (Fig. 248).
Any batrachian may easily be passed around the class after placing it
in a tumbler with gauze or net tied over top. It should be kept in a
box with two inches of moist earth on the bottom. If no live insects
are obtainable for feeding a toad, bits of moist meat may be dangled
from the end of a string. If tadpoles are placed in a pool or tub in
a garden, the toads hatched will soon make destructive garden insects
become a rarity.
Does a frog or a =salamander= have the more primitive form of body?
Why do you think so? Salamanders are sometimes called mud puppies. The
absurd belief that salamanders are poisonous is to be classed with
the belief that toads cause warts. The belief among the ancients that
salamanders ate fire arose perhaps from seeing them coming away from
fires that had been built over their holes on river banks by travelers.
Their moist skin protected them until the fire became very hot.
Describe the “mud puppy” shown in Fig. 262. In the West the pouched
gopher, or rat (Fig. 371), is sometimes absurdly called a salamander.
[Illustration: FIG. 262.--BLIND SALAMANDER (_Proteus anguinus_). × ¹⁄₂.
Found in caves and underground streams in Balkans. Gills external, tail
finlike, legs small.]
CHAPTER XII
REPTILIA (REPTILES)
This =class= is divided into _four orders_ which have such marked
differences of external form that there is no difficulty in
distinguishing them. These orders are represented by _Lizards_,
_Snakes_, _Turtles_, and _Alligators_. Of these, only the forms of
lizards and alligators have similar proportions, but there is a marked
difference in their size, lizards being, in general, the smallest, and
alligators the largest of the reptiles.
[Illustration: FIG. 263.--A SALAMANDER.]
[Illustration: FIG. 264.--A LIZARD.]
=Comparison of Lizards and Salamanders.=--To make clear the difference
between reptiles and batrachians, it will be well to compare the orders
in the two classes which resemble each other in size and shape; namely,
lizards and salamanders (Figs. 263 and 264). State in a tabular form
their differences in _skin, toe, manner of breathing, development from
egg, shape of tail, habitat, habits_. Each has an elongated body, two
pairs of limbs, and a long tail, yet they are easily distinguished. Are
the differences suggested above valid for the other batrachians (frogs)
and other reptiles (_e.g._ turtles)? Trace the same differences between
the toad or frog (Fig. 250) and the “horned toad,” which is a lizard
(Fig. 265).
[Illustration: FIG. 265.--“HORNED TOAD” LIZARD, of the Southwest
(_Phrynosoma cornita_). × ²⁄₃.]
STUDY OF A TURTLE OR TORTOISE
SUGGESTIONS.--Because of the ease with which a tortoise or turtle may
be caught and their movements and habits studied, it is suggested
that one of these be studied as an example of reptiles. Besides a
live specimen, a skeleton of one species and the shells of several
species should be available.
[Illustration: FIG. 266.--EUROPEAN POND TURTLE (_Emys lutaria_). (After
Brehms.)]
The =body (of a turtle or tortoise) is divided= distinctly into
_regions_ (Fig. 266). Is there a head? Neck? Trunk? Tail? The trunk is
inclosed by the _so-called shell_, which consists of an upper portion,
the _carapace_, and a lower portion, the _plastron_. How are the other
regions covered? What is the shape of the head? Is the mouth at the
front, or on the under side? Where are the _nostrils_? Are the motions
of breathing visible? Is there a beak or snout? Do the jaws contain
teeth?
Do the =eyes= project? Which is thinner and more movable, the upper or
lower lid? Identify the third eyelid (_nictitating membrane_). It is
translucent and comes from, and is drawn into, the inner corner of the
eye. It cleanses the eyeball. Frogs and birds have a similar membrane.
The circular =ear= drum is in a depression back of the angle of the
mouth. What other animal studied has an external ear drum?
The tortoise has a longer, more flexible =neck= than any other reptile.
Why does it have the greatest need for such a neck? Is the skin over
the neck tight or loose? Why?
Do the =legs= have the three joints or parts found on the limbs of most
vertebrates? How is the skin of the legs covered? Do the toes have
_claws_? Compare the front and hind feet. Does the tortoise slide its
body or lift it when walking on hard ground? Lay the animal on its back
on a chair or table at one side of the room in view of the class. Watch
its attempts to right itself. Are the motions suited to accomplish the
object? Does the tortoise succeed?
What are the prevailing =colors= of turtles? How does their coloration
correspond to their surroundings?
What parts of the tortoise extend at times beyond the shell? Are any of
these parts visible when the _shell is closed_? What movements of the
shell take place as it is closed? Is the carapace rigid throughout? Is
the plastron?
=The Skeleton= (Fig. 267).--The _carapace_ is covered with thin
_epidermal plates_ which belong to the skin. The bony nature of the
carapace is seen when the plates are removed, or if its inner surface
is viewed (Fig. 267). It is seen to consist largely of wide _ribs_ (how
many?) much flattened and grown together at their edges. The ribs are
seen to be rigidly attached to the vertebræ. The rear projections of
the vertebræ are flattened into a series of bony plates which take the
place of the sharp ridge found along the backs of most vertebrates.
Show that the shell of a turtle is not homologous with the shells of
mollusks. Does the turtle have shoulder blades and collar bones? Hip
bones? Thigh bones? Shin bone (fibia) and splint bone (fibula)? (Fig.
267.)
[Illustration: FIG. 267.--SKELETON OF EUROPEAN TORTOISE.
_C_, rib plates; _M_, marginal plates; _B_, plastron; _H_, humerus
bone; _R_, radius; _U_, ulna; _Fe_, femur.]
[Illustration: FIG. 268.--THREE-CHAMBERED HEART OF A REPTILE (tortoise).
_a_, veins; _b_, _f_, right and left auricles; _cg_, ventricle; _d_,
arteries to lungs; e, veins from lungs; _i_, _n_, two branches of
aorta. Compare with Fig. 269 and colored Fig. 2.]
Do the plates formed by the ribs extend to the edge of the carapace?
See Fig. 267. About how many bony plates form the carapace? The
plastron? Do the horny plates outside correspond to the bony plates of
the shell? How many axial plates? How many costal (rib) plates? How
many border plates? Which plates are largest? Smallest? Do the horny
plates overlap like shingles, or meet edge to edge? Is there any mark
where they meet on the bony shell? Basing it upon foregoing facts,
give a connected and complete description of the structure of the
carapace. Compare the skeleton of the turtle with that of the snake,
and correlate the differences in structure with differences in habits.
[Illustration: FIG. 269.--PLAN OF REPTILIAN CIRCULATION. See arrows.]
=Draw= the tortoise seen from the side or above, with its shell closed,
showing the arrangement of the plates.
Place soft or tender vegetable =food=, lettuce, mushroom, roots,
berries, and water, also meat, in reach of the turtle. What does it
prefer? How does it eat? It has no lips; how does it drink?
Study the =movements= of its eyeballs and eyelids, and the respiratory
and other movements already mentioned. State a reason for thinking
that no species of land animals exists that lacks the simple power of
righting itself when turned on its back.
[Illustration: FIG. 270.--REPTILIAN VISCERA (lizard).
_lr_, windpipe; _h_, heart; _lu_, lungs; _le_, liver; _ma_, stomach;
_dd_, _md_, intestines; _hb_, bladder.]
=Tortoise, Turtle, Terrapin.=--The turtles belong to the order of
reptiles called _chelonians_. No one can have any difficulty in knowing
a member of this order. The subdivision of the order into families is
not so easy, however, and the popular attempts to classify chelonians
as turtles, tortoises, and terrapins have not been entirely successful.
Species with a vaulted shell and imperfectly webbed toes and _strictly
terrestrial_ habits are called _tortoises_. Species with flattened
shells and _strictly aquatic_ habits should be called _terrapins_
(_e.g._ mud terrapin). They have three instead of two joints in the
middle toe of each foot. The term _turtle_ may be applied to species
which are _partly terrestrial and partly aquatic_ (_e.g._ snapping
turtle (Fig. 271)). Usage, however, is by no means uniform.
[Illustration: FIG. 271.--SNAPPING TURTLE (_Chelydra serpentina_).]
Most reptiles eat animal food; green terrapins and some land tortoises
eat vegetable food. Would you judge that carnivorous chelonians catch
very active prey?
The fierce _snapping turtle_, found in ponds and streams, sometimes has
a body three feet long. Its head and tail are very large and cannot be
withdrawn into the shell. It is carnivorous and has great strength of
jaw. It has been known to snap a large stick in two. The _box tortoise_
is yellowish brown with blotches of yellow, and like its close kinsman,
the pond turtle of Europe (Fig. 266), withdraws itself and closes its
shell completely. Both lids of the plastron are movable, a peculiarity
belonging to these two species. The _giant tortoise_ of the Galapagos
Islands, according to Lyddeker, can trot cheerfully along with three
full-grown men on its back. “Tortoise shell” used for combs and other
articles is obtained from the overlapping scales of the _hawkbill
turtle_, common in the West Indies. The _diamond-back terrapin_, found
along the Atlantic Coast from Massachusetts to Texas, is prized for
making soup.
[Illustration: FIG. 272.--A RATTLESNAKE.]
[Illustration: FIG. 273 _a_.--HEAD OF VIPER, showing typical triangular
shape of head of venomous snake.]
[Illustration: FIG. 273 _b_.--SIDE VIEW, showing poison fangs; also
tongue (forked, harmless).]
[Illustration: FIG. 274.--VIPER’S HEAD, showing poison sac at base of
fangs.]
[Illustration: FIG. 275.--SKULL, showing teeth, fangs, and quadrate
bone to which lower jaw is joined. See Fig. 284].
=Poisonous snakes of United States= named in order of virulence: 1.
Coral snakes, _Elaps_, about seventeen red bands bordered with yellow
and black (colored figure 6) (fatal). 2. Rattlesnakes (seldom fatal).
3. Copperhead (may kill a small animal size of dog). 4. Water moccasin
(never fatal). 5. Ground rattler.--_Effects_: Pulse fast, breathing
slow, blood tubes dilated, blood becomes stored in abdominal blood
tubes, stupefaction and death from blood being withdrawn from brain.
Always two punctures, the closer together the smaller the snake.
_Remedies_: Ligature between wound and heart, lance wound and suck;
inject into wound three drops of 1 per cent solution of chromic acid
or potassium permanganate. Give strychnine, hypodermically, until
strychnine symptoms (twitchings) appear. If symptoms of collapse recur,
repeat dose. Digitalin or caffein acts like strychnine; alcohol has
opposite effect.
[Illustration: FIG. 276.--“GLASS SNAKE,” a lizard without legs.]
[Illustration: FIG. 277.--SKULL OF ELAPS. See colored Fig. 5.]
[Illustration: FIG. 278.--SKULL OF LAMPROPELTIS.]
=Protective Coloration and Mimicry.=--When an animal imitates the color
or form of its _inanimate surroundings_ it is said to be _protectively
colored_ or formed. Give an instance of _protective coloration_or
_form_ among lizards; butterflies; grasshoppers; amphibians;
echinoderms. When an animal imitates the color or form of _another
animal_ it is said to _mimic_ the animal. Mimicry usually enables an
animal to deceive enemies into mistaking it for an animal which for
some reason they avoid. The milkweed butterfly has a taste that is
repulsive to birds. The viceroy butterfly is palatable to birds, but
it is left untouched because of its close resemblance to the repulsive
milkweed butterfly. The harlequin snake (_Elaps_) of the Gulf states
is the only deadly snake of North America (Figs. 277, 278). It is very
strikingly colored with rings of scarlet, yellow, and black. This is an
example of warning_ coloration_. The coral snake (_Lampropeltis_) has
bands of scarlet, yellow, and black (colored Fig. 6) of the same tints,
and it is hardly distinguishable from the harlequin. The coral snake
is said to _mimic_ the harlequin snake. It also imitates the quiet
inoffensive habits of the harlequin snake, which fortunately does not
strike except under the greatest provocation. The rattles of the less
poisonous and seldom fatal rattlesnake (Fig. 272) may be classed as an
example of _warning sound_ which most animals are quick to heed and
thus avoid encounters which might be destructive to either the snake or
its enemy.
[Illustration: FIG. 1
FIG. 2
FIG 3.
COLORED FIGURES 1, 2, 3.--CIRCULATION IN FISH, REPTILE, MAMMAL.
In which is blood from heart all impure? Mixed? Both pure and impure?]
[Illustration: FIG. 4.--ANATOMY OF CARP. For description see Fig. 220,
page 117.]
[Illustration: THE HARMLESS CORAL SNAKE MIMICS THE DEADLY HARLEQUIN
SNAKE.
FIG. 5.--HARLEQUIN SNAKE (_Elaps_).
FIG. 6.--CORAL SNAKE (_Lampropeltis_).]
[Illustration: FIG. 279.--GILA MONSTER (_Heloderma suspectum_), of
Arizona. If poisonous, it is the only instance among lizards. It is
heavy-built, orange and black mottled, and about 16 inches long.
Compare it with the green lizard (Fig. 280).]
[Illustration: FIG. 280.--CHAMELEON (_Anolis_), or green lizard of
southern U.S. Far excels European chameleon (Fig. 281) and all known
animals in power of changing color (green, gray, yellow, bronze, and
black).]
=Survival of the Fittest=.--The two facts of most far-reaching
importance in the history of animals and plants are: (1)
_Heredity_; animals inherit the characteristics of their parents.
(2) _Variation_; animals are not exactly like their parents. The
first fact gives stability, the second makes progress or evolution
possible. The climate of the world is slowly changing, and animals
must change to adapt themselves to it. A more sudden change of
environment (surroundings) of animals occurs because of migration or
isolation; these in turn are caused by the crowding of other animals
or by the formation or disappearance of geographical barriers, such
as deserts, water, mountain chains.
[Illustration: FIG. 281.--CHAMELEON OF SOUTHERN EUROPE.]
The young vary in many ways from their parents. Some have a more
protective color or form, sharper claws, swifter movements, etc.
The individuals possessing such beneficial variations live longer
and leave more offspring, and because of heredity transmit the
desirable qualities to some of their young. Variations which are
disadvantageous for getting food, defense, etc., cause shorter life
and fewer offspring. Thus the _fittest survive_, the unfit perish; an
automatic _natural selection_ occurs.
Darwin taught that variations are infinitesimal and gradual. Recent
experiments and observations seem to show that many variations are
by sudden jumps, somewhat resembling so-called “freaks of nature.”
As to whether these “sports,” or individuals with new peculiarities,
survive, depends upon their fitness for their environment. “Survival
of the fittest” results from this natural selection, but the
selection occurs between animals of marked, not infinitesimal,
differences, as Darwin taught. Darwin’s theory is probably true for
species in the usual state of nature; the new theory (of De Vries) is
probably true for animals and plants under domestication and during
rapid geographical changes.
[Illustration: FIG. 282.--EMBRYO OF A TURTLE, showing four gill slits.
(Challenger Report.)]
=Table for Review= (for notebooks or blackboards).
========================+========+========+========+========+========
| FISH | TADPOLE| FROG | TURTLE | LIZARD
------------------------+--------+--------+--------+--------+--------
| | | | |
Limbs, kind and number | | | | |
| | | | |
------------------------+--------+--------+--------+--------+--------
| | | | |
Are claws present? How | | | | |
many? | | | | |
| | | | |
------------------------+--------+--------+--------+--------+--------
| | | | |
Covering of body | | | | |
| | | | |
------------------------+--------+--------+--------+--------+--------
| | | | |
Teeth, kind of, if | | | | |
present | | | | |
| | | | |
------------------------+--------+--------+--------+--------+--------
| | | | |
Which bones found in man| | | | |
are lacking? | | | | |
| | | | |
------------------------+--------+--------+--------+--------+--------
| | | | |
Chambers of heart | | | | |
| | | | |
------------------------+--------+--------+--------+--------+--------
| | | | |
Respiration | | | | |
| | | | |
------------------------+--------+--------+--------+--------+--------
| | | | |
Movements | | | | |
| | | | |
========================+========+========+========+========+========
[Illustration: FIG. 283.--BIG-HEADED TURTLE (_Platysternum
megalocephalum_). × ¹⁄₂. China. This and Fig. 282 suggest descent of
turtles from a lizardlike form. Figure 282 shows earlier ancestors to
have been gill breathers.]
CHAPTER XIII
BIRDS
[Illustration]
SUGGESTIONS.--The domestic pigeon, the =fowl=, and the English
sparrow are most commonly within the reach of students. The last
bird has become a pest and is almost the only bird whose destruction
is desirable. The female is somewhat uniformly mottled with gray
and brown in fine markings. The male has a black throat with the
other markings of black, brown, and white, in stronger contrast
than the marking of the female. As the different species of birds
are essentially alike in structural features, the directions and
questions may be used with any bird at hand. When studying feathers,
one or more should be provided for each pupil in the class. The feet
and bills of birds should be kept for study.
Does the =body of the bird=, like the toad and turtle, have a head,
trunk, tail, and two pairs of limbs? Do the fore and hind limbs differ
from each other more or less than the limbs of other backboned animals?
Does any other vertebrate use them for purposes as widely different?
=Eye.=--Does the _eyeball_ have parts corresponding to the eyeball of
a fish or frog; viz., cornea, iris, pupil? Which is more movable, the
upper or lower _eyelid_? Are there any lashes? The bird (like what
other animal?) has a third eyelid, or nictitating membrane. Compare its
thickness with that of the other lids. Is it drawn over the eyeball
from the inner or outer corner of the eye? Can you see in the human eye
any wrinkle or growth which might be regarded as remains, or vestige,
of such a membrane?
How many =nostrils=? In which mandible are they located? Are they
nearer the tip or the base of the mandible? (Fig. 284.) What is their
shape? Do the nasal passages go directly down through the mandible or
do they go backward? Is the inner nasal opening into the mouth or into
the throat?
The beak or =bill= consists of the upper and lower mandibles. The
outside of the beak seems to be of what kind of material? Examine the
decapitated head of a fowl or of a dissected bird, and find if there is
a covering on the bill which can be cut or scraped off. Is the mass of
the bill of bony or horny material? With what part of the human head
are the mandibles homologous? (Fig. 284.)
[Illustration: FIG. 284.--SKULL OF DOMESTIC FOWL.
_q_, quadrate (“four-sided”) bone by which lower jaw is attached to
skull (wanting in beasts, present in reptiles; see Fig. 277).]
=Ears.=--Do birds have external ears? Is there an _external opening_
leading to the ear? In searching for it, blow or push forward the
feathers. If found, notice its location, size, shape, and what
surrounds the opening. There is an owl spoken of as the long-eared owl.
Are its ears long?
The =leg= has three divisions: the uppermost is the _thigh_ (called
the “second joint” in a fowl); the middle division is the _shank_
(or “drumstick”); and the lowest, which is the slender bone covered
with scales, is formed by the union of the _ankle_ and _instep_. (The
bones of the three divisions are named the femur, tibiotarsus, and
tarsometatarsus). The _foot_ consists entirely of toes, the bones of
which are called phalanges. Is there a bone in each claw? (See Fig.
285.) Supply the numerals in this sentence: The pigeon has ____ toes,
the hind toe having ____ joints; of the three front toes, the inner has
____ joints (count the claw as one joint), the middle has ____ joints,
and the outer toe has ____ joints (Fig. 285). Is the thigh of a bird
bare or feathered? The shin? The ankle? Where is the ankle joint of
a bird? Do you see the remains of another bone (the splint bone, or
fibula) on the shin bone of the shank? (Fig. 285 or 286.) Why would
several joints in the ankle be a disadvantage to a bird?
[Illustration: FIG. 285.--LEG BONES OF BIRD.]
[Illustration: FIG. 286.--SKELETON OF BIRD.
_Rh_, vertebræ; _Cl_, clavicle; _Co_, coracoid; _Sc_, scapula; _St_,
sternum; _H_, humerus; _R_, radius; _U_, ulna; _P_, thumb; _Fe_, femur;
_T_, tibia. See Fig. 394.
=Questions:= Which is the stiffest portion of the vertebral column? How
are the ribs braced against each other? Which is longer, thigh bone or
shin? Compare shoulder blade with man’s (Fig. 399). Which is the extra
shoulder bone? Compare tail vertebræ with those of extinct bird, Fig.
290.]
The _thigh_ hardly projects beyond the skin of the trunk, as may be
noticed in a plucked fowl. The thigh extends forward from the hip joint
(Figs. 286, 299) in order to bring the point of support forward under
the center of weight. Why are long front toes more necessary than long
hind toes? As the bird must often bring its head to the ground, the hip
joints are near the dorsal surface and the body swings between the two
points of support somewhat like a silver ice pitcher on its two pivots.
Hence stooping, which makes a man so unsteady, does not cause a bird to
lose steadiness.
The =wing= has three divisions which correspond to the upper arm,
forearm, and hand of man (Fig. 286). When the wing is folded, the three
divisions lie close alongside each other. Fold your arm in the same
manner. The similarity of the bones of the first and second divisions
to the bones of our upper _arm_ and _forearm_ is very obvious (Fig.
286). Explain. The _hand_ of a bird is furnished with only three digits
(Fig. 287). The three palm bones (metacarpals) are firmly united (Fig.
287). This gives firmness to the stroke in flying.
[Illustration: FIG. 287.--HAND AND WRIST OF FOWL (after Parker).
_DG. 1-3_, digits; _MC. 1-3_, metacarpals; _CC. 3_, wrist.]
[Illustration: FIG. 288.--HAND, WRIST (_c_), FOREARM, AND ELBOW OF
YOUNG CHICK (after Parker).]
That the bird is _descended from animals_ which had the fingers and
palm bones less firmly united is shown by comparing the hands of
a _chick_ and of an _adult_ fowl (Figs. 287, 288). The wrist also
solidifies with age, the five carpals of the chick being reduced to two
in the fowl (Figs. 287, 288). The thumb or first digit has a separate
covering of skin from the other digits, as may be seen in a plucked
bird. The degenerate hand of the fowl is of course useless as a hand
(what serves in its place?) but is well fitted for firm support of
the feathers in flying. The two bones of the forearm are also firmly
joined. There are eighteen movable joints in our arm and hand; the bird
has only the three joints which enable it to fold its wing. The wrist
joint is the joint in the forward angle of the wing.
[Illustration: FIG. 289.--BREASTBONE AND SHOULDER BONES OF CASSOWARY.]
[Illustration: FIG. 290.--A FOSSIL BIRD (_archæopteryx_) found in the
rocks of a former geological epoch.
=Question:= Find two resemblances to reptiles in this extinct bird
absent from skeletons of extant birds.]
Since the fore limbs are taken up with locomotion, the =grasping
function= has been assumed by the _jaws_. How does their shape adapt
them to this use? For the same reason the _neck_ of a bird surpasses
the necks of all other animals in what respect? Is the trunk of a bird
flexible or inflexible? There is thus a _correlation_ between structure
of neck and trunk. Explain. The same correlation is found in which of
the reptiles? (Why does rigidity of trunk require flexibility of neck?)
Why does the length of neck in birds correlate with the length of legs?
Examples? (See Figs. 314, 315, 332.) Exceptions? (Fig. 324.) Why does a
swan or a goose have a long neck, though its legs are short?
To make a firm support for the wings the vertebræ of the back are
immovably joined, also there are three bones in each shoulder, the
collar bone, the shoulder blade, and the coracoid bone (Fig. 286). The
collar bones are united (why?) and form the “wishbone” or “pulling
bone.” To furnish surface for the attachment of the large flying
muscles there is a prominent ridge or keel on the breastbone (Fig.
286). It is lacking in most birds which do not fly (Fig. 289).
[Illustration: FIG. 291.--QUILL FEATHER.
_D_, downy portion.]
The =feathers= are perhaps the most characteristic feature of birds.
The large feathers of the wings and tail are called _quill feathers_. A
quill feather (Fig. 291) is seen to consist of two parts, the _shaft_,
or supporting axis, and the broad _vane_ or web. What part of the shaft
is round? Hollow? Solid? Is the shaft straight? Are the sides of the
vane usually equal in width? Can you tell by looking at a quill whether
it belongs to the wing or tail, and which wing or which side of the
tail it comes from? Do the quills overlap with the wide side of the
vane above or beneath the next feather? Can you cause two parts of the
vane to unite again by pressing together the two sides of a split in
the vane? Does the web separate at the same place when pulled until it
splits again?
[Illustration: FIG. 292.--I, CONTOUR FEATHER. II, III, PARTS OF QUILL
FEATHER, enlarged.]
The hollow part of the shaft of a quill feather is called the _quill_.
The part of the shaft bearing the vane is called the _rachis_ (rā-kis).
The vane consists of slender _barbs_ which are branches of the shaft
(II, Fig. 292). As the name indicates (see dictionary), a barb
resembles a hair. The barbs in turn bear secondary branches called
_barbules_, and these again have shorter branches called _barbicels_
(III, Fig. 292). These are sometimes bent in the form of hooklets (Fig.
292, III), and the hooklets of neighboring barbules interlock, giving
firmness to the vane. When two barbules are split apart, and then
reunited by stroking the vane between the thumb and finger, the union
may be so strong that a pull upon the vane will cause it to split in a
new place next time.
[Illustration: FIG. 293.--A DOWN FEATHER, enlarged.]
There are =four kinds= of feathers, (1) the _quill_ feathers, just
studied; (2) the _contour_ feathers (I, Fig. 292), which form the
general surface of the body and give it its outlines; (3) the _downy_
feathers (Fig. 293), abundant on nestlings and found among the contour
feathers of the adult but not showing on the surface; (4) the _pin_
feathers, which are hair-like, and which are removed from a plucked
bird by singeing. The contour feathers are similar in structure to the
quill feathers. They protect the body from blows, overlap so as to shed
the rain, and, with the aid of the downy feathers retain the heat, thus
accounting for the high temperature of the bird. The downy feathers are
soft and fluffy, as they possess few or no barbicels; sometimes they
lack the rachis (Fig. 293). The pin feathers are delicate horny shafts,
greatly resembling hairs, but they may have a tuft of barbs at the ends.
A =feather grows= from a small projection (or papilla) found at the
bottom of a depression of the skin. The quill is formed by being molded
around the papilla. Do you see any opening at the tip of the quill for
blood vessels to enter and nourish the feather? What is in the quill?
(Fig. 291.) The rachis? A young contour or quill feather is inclosed in
a delicate sheath which is cast off when the feather has been formed.
Have you seen the sheath incasing a young feather in a molting bird?
There are considerable =areas= or tracts on a bird’s skin =without
contour feathers=. Such bare tracts are found along the ridge of the
breast and on the sides of the neck. However, the contour feathers lie
so as to overlap and cover the whole body perfectly (Fig. 294).
[Illustration: FIG. 294.--DORSAL AND VENTRAL VIEW OF PLUCKED BIRD,
showing regions where feathers grow.]
The shedding of the feathers is called =molting=. Feathers, like the
leaves of trees, are delicate structures and lose perfect condition
with age. Hence the annual renewal of the feathers is an advantage.
Most birds shed twice a year, and with many the summer plumage is
brighter colored than the winter plumage. When a feather is shed on
one side, the corresponding feather on the other side is always shed
with it. (What need for this?) A large _oil gland_ is easily found on
the dorsal side of the tail. How does the bird apply the oil to the
feathers?
[Illustration: FIG. 295.--WING OF BIRD.
_1_, false quills (on thumb); _2_, primaries; _3_, secondaries;
tertiaries (dark) are one above another at right; _a_, _b_, coverts.]
[Illustration: FIG. 296.
_A_, point dividing primaries from secondaries; _B_, coverts.]
[Illustration: FIG. 297.--CEDAR WAXWING, with regions of body marked.
_S_, forehead; _Sc_, crown (with crest); _Hh_, nape; _K_, throat; _Br_,
breast; _Ba_, lower parts; _R_, back; _Rt_, tail; _B_, tail coverts;
_P_, shoulder feathers (scapulars); _T_, wing coverts; _HS_, primaries;
_AS_, secondaries; _Al_, thumb feathers.]
In describing and classifying birds, it is necessary to know the names
of the various external =regions= of the body and plumage. These may
be learned by studying Figs. 295, 296, 297, 298. The quills on the
hand are called primaries, those on the forearm are the secondaries,
those on the upper arm are the tertiaries. Those on the tail are called
the _tail quills_. The feathers at the base of the quills are called
the _coverts_. The thumb bears one or more quills called the spurious
quills. Is the wing concave on the lower or upper side? What advantage
is this when the bird is at rest? When it is flying?
[Illustration: FIG. 298.--PLAN OF BIRD. _s_, center of gravity.]
[Illustration: FIG. 299.--POSITION OF LIMBS OF PIGEON.]
=Control of Flight.=--Did you ever see a bird sitting on a swinging
limb? What was its chief means of balancing itself? When flying, what
does a bird do to direct its course upward? Downward? Is the body level
when it turns to either side? Birds with long, pointed wings excel in
what respect? Examples? Birds with great wing surface excel in what
kind of flight? Examples. Name a common bird with short wings which has
a labored, whirring flight. Is its tail large or small? Does it avoid
obstacles and direct its flight well? Why or why not? When a boat is to
be turned to the right, must the rudder be pulled to the right or the
left? (The rudder drags in the water and thus pulls the boat around.)
When the bird wishes to go upward, must its tail be turned up or down?
How when it wishes to go down? When a buzzard soars for an hour without
flapping its wings, does it move at a uniform rate? For what does it
use the momentum gained when going with the wind?
[Illustration: FIG. 300.
_a_, clambering foot of chimney sweep; _b_, climbing foot of
woodpecker; _c_, perching foot of thrush; _d_, seizing foot of hawk;
_e_, scratching foot of pheasant; _f_, stalking foot of kingfisher;
_g_, running foot of ostrich; _h_, wading foot of heron; _i_, paddling
foot of gull; _k_, swimming foot of duck; _l_, steering foot of
cormorant; _m_, diving foot of grebe; _n_, skimming foot of coot.
=Question:= Does any bird use its foot as a hand? (Fig. 320.)]
=Flying.=--When studying the quill feathers of the wing, you saw that
the wider side of the vane is beneath the feather next behind it.
During the downward stroke of the wing this side of the vane is pressed
by the air against the feather above it and the air cannot pass through
the wing. As the wing is raised the vanes separate and the air passes
through. The convex upper surface of the wing also prevents the wing
from catching air as it is raised. Spread a wing and blow strongly
against its lower surface; its upper surface. What effects are noticed?
Study the =scales= on the leg of a bird (Fig. 300). Why is the leg
scaly rather than feathered from the ankle downward? Which scales are
largest? (Fig. 300.) How do the scales on the front and back differ?
What can you say of the scales at the bottom of the foot; at the joints
of the toes? Explain. How does the covering of the nails and bill
compare in color, texture, hardness and firmness of attachment with the
scales of the leg?
[Illustration: FIG. 301.--AN ALTRICAL BIRD, _i.e._ poorly developed at
hatching. Young pigeon, naked, beak too weak for eating.]
[Illustration: FIG. 302.--A PRECOCIAL BIRD (well developed at
hatching). Feathered, able to run and to pick up food. Precocity is a
sign of instinctive life and low intelligence. A baby is not precocious.
=Question:= Is pigeon or fowl exposed to more dangers in infancy?]
=Draw= an outline of the bird seen from the side. Make drawings of the
head and feet more detailed and on a larger scale.
Why does a goose have more feathers suitable for making pillows than a
fowl? In what country did the domestic fowl originate? (Encyclopedia.)
Why does a cock crow for day? (Consider animal life in jungle.)
=Activities of a Bird.=--Observe a bird _eating_. Does it seem to chew
or break its food before swallowing? Does it have to lift its head in
order to swallow food? To swallow drink? Why is there a difference?
After feeding the bird, can you feel the food in the crop, or
enlargement of the gullet at the base of the neck? (Fig. 304.)
Feel and look for any movements in _breathing_. Can you find how often
it breathes per minute? Place hand under the bird’s wing. What do you
think of its _temperature_; or better, what temperature is shown by
a thermometer held under its wing? Do you see any connection between
the breathing rate and the temperature? Test (as with the crayfish)
whether a bird can _see_ behind its head? Notice the movements of the
nictitating membrane. Does it appear to be transparent?
Watch a bird _fly_ around a closed room and review the questions on
Control of Flight.
_Bend_ a bird’s leg and see if it has any effect upon its toes. Notice
a bird (especially a large fowl) walk to see if it bends its toes as
the foot is lifted. Pull the rear tendon in a foot cut from a fowl for
the kitchen. Does the bird have to use muscular exertion to _grasp_ a
stick upon which it sits? Why, or why not? When is this bending of the
toes by bending the legs of special advantage to a hawk? To a duck? A
wading bird? Why is a fowl safe from a hawk if it stands close to a
tree?
[Illustration: FIG. 303.--HEAD OF WOODPECKER.
_c_, tongue; _a_, _b_, _d_, hyoid bone; _e_, _q_, windpipe; _f_,
salivary gland.]
Do you see any signs of teeth in the bird’s jaws? Why are duck’s
“teeth” (so called by children) not teeth? Can the tongue of a bird be
pulled forward? (Fig. 303.) What is its shape? If there is opportunity,
dissect and study the slender, bony (hyoid) apparatus to which the base
of the tongue is attached (Fig. 303), the opening of the windpipe, or
trachea, the slit-like opening of windpipe which is so narrow as to
prevent food falling into the windpipe.
[Illustration: FIG. 304.--ANATOMY OF DOVE × ¹⁄₂.
_bk_, keel of breastbone; _G_, _g_, brain; _lr_, windpipe; _lu_, lung;
_h_, heart; _sr_, gullet; _k_, crop; _dr_, glandular stomach; _mm_,
gizzard; _d_, intestine; _n_, kidney; _hl_, ureter; _eil_, openings of
ureter and egg duct into cloaca, _kl_.]
[Illustration: FIG. 305.--FOOD TUBE OF BIRD.
_P_, pancreas; _C_, cæca.
=Question:= Identify each part by means of Fig. 304.]
=The Internal Organs, or Viscera= (Figs. 304 and 305).--The viscera
(vis′se-ra), as in most vertebrates, _include_ the food tube and its
glands; the lungs, the heart, and larger blood vessels; the kidneys
and bladder and the reproductive organs. The lower part, or gullet,
is enlarged into a _crop_. It is largest in grain-eating birds. It
is found in the V-shaped depression at the angle of the wishbone,
just before the food tube enters the thorax. The food is stored and
softened in the crop. From the crop the food passes at intervals into
the glandular stomach. Close to this is the muscular stomach, or
gizzard. Are the places of entrance and exit on opposite sides of the
gizzard, or near together? (Fig. 304.) Is the lining of the gizzard
rough or smooth? Why? Is the gizzard tough or weak? Why are small
stones in the gizzard? Why do not hawks and other birds of prey need a
muscular gizzard? The liver and pancreas empty their secretions into
the intestines by several ducts a little way beyond the gizzard. Beyond
the mouths of two cæca (Fig. 305) the many-coiled intestine empties
into the straight rectum, which terminates in a widened part called
the cloaca. Not only the intestine, but the two ureters of the urinary
system and the two genital ducts of the reproductive system all empty
into the cloaca (Figs. 304, 305).
[Illustration: FIG. 306.--POSITION OF LUNGS AND AIR SACS (Pigeon).
_Tr_, windpipe; _P_, lungs; _Lm_, sac under clavicle with prolongation
(_Lh_) into humerus; _La_, sacs in abdomen.]
The =lungs= have their rear surfaces attached to the spinal column and
ribs (_lu_, Fig. 304). They are connected with thin-walled, transparent
_air sacs_ which aid in purifying the blood. When inflated with warm
air, they probably make the body of the bird more buoyant. For the
names, location, and shape of several pairs of air sacs, see Fig. 306.
The connection of the air sacs with hollows in the humerus bones is
also shown in the figure. Many of the _bones are hollow_; this adds to
the buoyancy of the bird. The pulmonary artery, as in man, takes dark
blood to the lungs to exchange its carbon dioxide for oxygen. Of two
animals of the same weight, which expends more energy, the one that
flies, or the one that runs the same distance? Does a bird require more
oxygen or less, in proportion to its weight, than an animal that lives
on the ground? Are the vocal cords of a bird higher or lower in the
windpipe than those of a man? (Fig. 307.)
The heart of a bird, like a man’s heart, has four chambers; hence it
keeps the purified blood separate from the impure blood. Since pure
blood reaches the organs of a bird, oxidation is more perfect than in
the body of any animals yet studied. Birds have higher temperature than
any other class of animals whatsoever. Tell how the jaws, tail, and
wings of the fossil bird Archæopteryx differed from living birds (Fig.
290).
[Illustration: FIG. 307.--POSITION OF VOCAL CORDS (_str_) OF MAMMAL AND
BIRD.
=Question:= Does a fowl ever croak after its head and part of its neck
are cut off? Explain.]
SUGGESTIONS.--In the field work, besides seeking the answers to
definite questions, pupils may be required to hand in a record of the
places and times of seeing a certain number of birds (20 to 40), with
the actions and features which made each distinguishable. Also, and
more important, each pupil should hand in a record of a careful and
thorough outdoor study of one common species (see below) as regards
habits, nesting, relation to environment, etc.
=Field Study of a Common Species.=--(_For written report._) Name of
species. _Haunts._ Method of locomotion when not flying. _Flying_
(rate, sailing, accompanying sound if any, soaring).
What is the _food_? How obtained? _Association_ with birds of its own
species. _Relation_ to birds of other species.
Where does it build its _nest_? Why is such a situation selected? Of
what is the nest built? How is the material carried, and how built
into the nest? Does the bird’s body fill the nest?
Describe the _eggs_. Does the male bird ever sit or otherwise assist
female before hatching? Does it assist after hatching?
How long is taken to lay a sitting of eggs? How long before the birds
are hatched? _When hatched_ are they helpless? Blind? Feathered? (Figs.
301, 302.) Do the nestlings require much food? How many times is food
brought in an hour? How distributed? Even if the old birds sometimes
eat fruit do they take fruit to the young? What do they feed to the
young? How long before they leave the nest? Do the parents try to teach
them to fly? Do the parents care for them after the nest is left? What
songs or calls has the bird?
[Illustration: FIG. 308.--EUROPEAN TOMTIT’S NEST. What are the
advantages of its shape?]
[Illustration: FIG. 309.--TAILOR BIRD’S NEST (India).
Instinct for nest building highly perfected.]
=General Field Study.=--(_For written report._) Name the best and
poorest flyers you know; birds that fly most of the time; birds that
seldom fly. Observe birds that pair; live in flocks. Does their
sociability vary with the season? Do you ever see birds quarreling?
Fighting? What birds do you observe whipping or driving birds larger
than themselves? Which parent do young birds most resemble? Name the
purposes for which birds sing. Which senses are very acute? Why?
Dull? Why? Can you test your statements by experiment? A partridge
usually sits with 18 to 24 eggs in nest. About how long after laying
first egg before sitting begins? Do several partridge hens lay in the
same nest?
[Illustration: FIG. 310.--HOUSE WREN.]
_Haunts._--Name some birds that are found most often in the following
localities: about our homes, in gardens and orchards, fields and
meadows, in bushes, in the woods, in secluded woods, around streams
of water, in thickets, in pine woods.
_Size._--Name birds as large as a robin or larger, nearly as large,
half as large, much smaller.
_Colors._--Which sex is more brilliant? What advantage are bright
colors to one sex? What advantage are dull colors to the other sex?
Which have yellow breasts, red patch on heads, red or chestnut
breasts, blue backs, black all over?
_Habits._--Name the birds that walk, jump, swim, live in flocks, sing
while flying, fly in undulations, in circles, have labored flight.
Such books as Wright’s “Birdcraft” (Macmillan, N. Y.), Clark’s “Birds
of Lakeside and Prairie” (Mumford, Chicago), and Pearson’s “Stories
of Bird Life” (B. F. Johnson, Richmond), will be of great help. The
last book is delightfully written, and is one of the few treating of
bird life in the South.
=Economic Importance of Birds.=--Farmers find their most valuable
allies in the class _aves_, as birds are the deadliest enemies of
insects and gnawing animals. To the innumerable robbers which devastate
our fields and gardens, nature opposes the army of birds. They are
less numerous than insects and other robbers, it is true, but they
are skillful and zealous in pursuit, keen of eye, quick, active, and
remarkably voracious. The purely insectivorous birds are the most
useful, but the omnivorous and graminivorous birds do not disdain
insects. _The perchers and the woodpeckers should be protected most
carefully._ The night birds of prey (and those of the day to a less
degree) are very destructive to field mice, rabbits, and other gnawing
animals. Some ignorant farmers complain continually about the harm done
by birds. To destroy them is as unwise as it would be to destroy the
skin which protects the human body because it has a spot upon it! It
cannot be repeated too plainly that to hunt useful birds is a wrong and
mischievous act, and it is stupid and barbarous to destroy their nests.
[Illustration: FIG. 311.--SCREECH OWL (_Megascops asio_).
=Question:= Compare posture of body, position of eyes, and size of
eyes, with other birds.]
[Illustration: FIG. 312.--GOSHAWK, or chicken hawk.]
Injurious birds are few. Of course birds which are the enemies of other
birds are enemies of mankind, but examples are scarce (some owls and
hawks). Many birds of prey are classed thus by mistake. Sparrow hawks,
for instance, do not eat birds except in rare instances; they feed
chiefly upon insects. A sparrow hawk often keeps watch over a field
where grasshoppers are plentiful and destroys great numbers of them.
When a bird is killed because it is supposed to be injurious, the
crop should always be examined, and its contents will often surprise
those who are sure it is a harmful bird. The writer once found two
frogs, three grasshoppers, and five beetles that had been swallowed
by a “chicken hawk” killed by an irate farmer, but no sign of birds
having been used for food. Fowls should not be raised in open places,
but among trees and bushes, where hawks cannot swoop. Birds which live
exclusively upon fish are, of course, opposed to human interests.
Pigeons are destructive to grain; eagles feed chiefly upon other birds.
[Illustration: FIG. 313.--ROAD RUNNER, or chaparral bird (Tex. to
Cal.). What order? (Key, p. 177.)]
If the birds eat the grapes, do not kill the birds, but plant more
grapes. People with two or three fruit trees or a small garden are
the only ones that lose a noticeable amount of food. We cut down the
forests from which the birds obtain part of their food. We destroy
insect pests at great cost of spraying, etc. The commission the birds
charge for such work is very small indeed. (See pages 177-183.)
[Illustration: FIG. 314.--WOOD DUCK, male (_Aix sponsa_). Nests in
hollow trees throughout North America. Also called summer duck in
South. Why?]
The =English sparrow= is one bird of which no good word may be said.
Among birds, it holds the place held by rats among beasts. It is
crafty, quarrelsome, thieving, and a nuisance. It was imported in 1852
to eat moths. The results show how ignorant we are of animal life, and
how slow we should be to tamper with the arrangements of nature. In
Southern cities it produces five or six broods each year with four to
six young in each brood. (Notice what it feeds its young.) It fights,
competes with and drives away our native useful birds. It also eats
grain and preys upon gardens. They have multiplied more in Australia
and the United States than in Europe, because they left behind them
their native enemies and their new enemies (crows, jays, shrikes,
etc.) have not yet developed, to a sufficient extent, the habit of
preying upon them. Nature will, perhaps, after a long time, restore the
equilibrium destroyed by presumptuous man.
=Protection of Birds.=--1. Leave as many trees and bushes standing as
possible. Plant trees, encourage bushes.
2. Do not keep a cat. A mouse trap is more useful than a cat. A tax
should be imposed upon owners of cats.
3. Make a bird house and place on a pole; remove bark from pole that
cats may not climb it, or put a broad band of tin around the pole.
4. Scatter food in winter. In dry regions and in hot weather keep a
shallow tin vessel containing water on the roof of an outhouse, or
out-of-the-way place for shy birds.
5. Do not wear feathers obtained by the killing of birds. What feathers
are not so obtained?
6. Report all violators of laws for protection of birds.
7. Destroy English sparrows.
[Illustration: FIG. 315.--GREAT BLUE HERON. In flight, balancing with
legs.]
=Migration.=--Many birds, in fact most birds, migrate to warmer
climates to spend the winter. Naturalists were once content to speak
of the migration of birds as a wonderful instinct, and made no attempt
to explain it. As birds have the warmest covering of all animals,
the winter migration is not for the purpose of escaping the cold; it
is probably to escape starvation, because in cold countries food is
largely hidden by snow in winter. On the other hand, if the birds
remained in the warm countries in summer, the food found in northern
countries in summer would be unused, while they would have to compete
with the numerous tropical birds for food, and they and their eggs
would be in danger from snakes, wild cats, and other beasts of prey so
numerous in warm climates. These are the best reasons so far given for
migration.
[Illustration: FIG. 316.--EUROPEAN SWALLOWS (_Hirundo urbica_),
assembling for autumn flight to South.]
The =manner= and =methods of migration= have been studied more
carefully in Europe than in America. Migration is not a blind,
infallible instinct, but the route is learned and taught by the old
birds to the young ones; they go in flocks to keep from losing the
way (Fig. 316); the oldest and strongest birds guide the flocks (Fig.
317). The birds which lose their way are young ones of the last brood,
or mothers that turn aside to look for their strayed young. The adult
males seldom lose their way unless scattered by a storm. Birds are
sometimes caught in storms or join flocks of another species and arrive
in countries unsuited for them, and perish. For example, a sea or marsh
bird would die of hunger on arriving in a very dry country.
[Illustration: FIG. 317.--CRANES MIGRATING, with leader at point of
V-shaped line.]
The =landmarks of the route= are mountains, rivers, valleys, and coast
lines. This knowledge is handed down from one generation to another.
It includes the location of certain places on the route where food is
plentiful and the birds can rest in security. Siebohm and others have
studied the routes of migration in the Old World. The route from the
nesting places in northern Europe to Africa follows the Rhine, the Lake
of Geneva, the Rhone, whence some species follow the Italian and others
the Spanish coast line to Africa. Birds choose the lowest mountain
passes. The Old World martin travels every year from the North Cape to
the Cape of Good Hope and back again! Another route has been traced
from Egypt along the coast of Asia Minor, the Black Sea and Ural Mts.
to Siberia.
=Field Study of Migration.=--Three columns may be filled on the
blackboard in an unused corner, taking several months in spring or fall
for the work. _First_ column, birds that stay all the year. _Second_
column, birds that come from the south and are seen in the summer
only. _Third_ column, birds that come from the north and are seen in
winter only. Exact dates of arrival and departure and flight overhead
should be recorded in notebooks. Many such records will enable American
zoologists to trace the migration routes of our birds. Reports may be
sent to the chief of the Biological Survey, Washington, D.C.
[Illustration: FIG. 318.--APTERYX, of New Zealand. Size of a hen, wings
and tail rudimentary, feathers hair-like.]
=Molting.=--How do birds arrange their feathers after they have been
ruffled? Do they ever bathe in water? In dust? Dust helps to remove old
oil. At what season are birds brightest feathered? Why? Have you ever
seen evidence of the molting of birds? Describe the molting process
(page 120).
[Illustration: FIG. 319.--GOLDEN, SILVER, AND NOBLE PHEASANTS, males.
Order? (Key, p. 177.) Ornaments of males, brightest in season of
courtship, are due to sexual selection (Figs. 321-7-9, 333).]
[Illustration: FIG. 320.--COCKATOO.]
[Illustration: FIG. 321.--BIRD OF PARADISE (Asia).]
=Adaptations for Flying.=--Flight is the most difficult and
energy-consuming method of moving found among animals, and careful
adjustment is necessary. For balancing, the heaviest muscles are
placed at the lower and central portion of the body. These are the
flying muscles, and in some birds (humming birds) they make half of
the entire weight. Teeth are the densest of animal structures; teeth
and the strong chewing muscles required would make the head heavy
and balancing difficult; hence the chewing apparatus is transferred
to the heavy gizzard near the center of gravity of the body. The
bird’s neck is long and excels all other necks in flexibility, but
it is very slender (although apparently heavy), being inclosed in a
loose, feathered skin. A cone is the best shape to enable the body to
penetrate the air, and a small neck would destroy the conical form. The
internal organs are compactly arranged and rest in the cavity of the
breast bone. The bellows-like air sacs filled with warm air lighten
the bird’s weight. The bones are hollow and very thin. The large tail
quills are used by the bird only in guiding its flight up and down,
or balancing on a limb. The feet also aid a flying bird in balancing.
The wing is so constructed as to present to the air a remarkably large
surface compared with the small bony support in the wing skeleton. Are
tubes ever resorted to by human architects when lightness combined with
strength is desired? Which quills in the wing serve to lengthen it?
(Fig. 296.) To broaden it? Is flight more difficult for a bird or a
butterfly? Which of them do the flying machines more closely resemble?
Can any bird fly for a long time without flapping its wings?
[Illustration: FIG. 322.--HERRING GULL. (Order?)]
=Exercise in the Use of the Key.=--Copy this list and write the name
of the order to which each of the birds belongs. (Key, page 177.)
Cockatoo (Fig. 320)
Sacred Ibis (Fig. 328)
Screech Owl (Fig. 311)
Nightingale (Fig. 325)
Top-knot Quail (Fig. 329)
Wren (Fig. 310)
Apteryx (Fig. 318)
Lyre bird (Fig. 327)
Road Runner (Fig. 313)
Ostrich (Fig. 332)
Penguin (Fig. 330)
Pheasant (Fig. 319)
Wood Duck (Fig. 314)
Jacana (Fig. 324)
Sea Gull (Fig. 322)
Heron (Fig. 315)
Hawk (Fig. 312)
KEY, OR TABLE, FOR CLASSIFYING BIRDS (_Class Aves_) INTO ORDERS
ORDERS
A₁ =Wings not suited for flight=, 2 or 3 toes RUNNERS
A₂ =Wings suited for flight= (except the penguin)
B₁ _Toes united by a web for swimming, legs short_
C₁ Feet placed far back; wings short, tip not DIVERS
reaching to base of tail (Fig. 300)
C₂ Bill flattened, horny plates under margin of BILL-STRAINERS
upper bill (Fig. 323)
C₃ Wings long and pointed, bill slender SEA-FLIERS
C₄ All four toes webbed, bare sac under throat GORGERS
B₂ _Toes not united by web for swimming_
C₁ Three front toes, neck and legs long, tibia WADERS
(shin, or “drumstick”) partly bare
C₂ Three front toes, neck and legs not long
D₁ Claws short and blunt (_e_, Fig. 300)
E₁ Feet and beak stout, young feathered, SCRATCHERS
base of hind toe elevated
E₂ Feet and beak weak, young naked MESSENGERS
D₂ Claws long, curved and sharp, bill hooked ROBBERS
and sharp
D₃ Claws long, slightly curved, bill nearly PERCHERS
straight
C₃ Two front and two hind toes (Fig. 300)
D₁ Bill straight, feet used for climbing FOOT-CLIMBERS
D₂ Bill hooked, both bill and feet used for BILL-CLIMBERS
climbing
=The Food of Birds.=--Extracts from Bulletin No. 54 (United States
Dept. of Agriculture), by F. E. L. Beal.
The practical value of birds in controlling insect pests should be
more generally recognized. It may be an easy matter to exterminate
the birds in an orchard or grain field, but it is an extremely
difficult one to control the insect pests. It is certain, too,
that the value of our native sparrows as weed destroyers is not
appreciated. Weed seed forms an important item of the winter food of
many of these birds, and it is impossible to estimate the immense
numbers of noxious weeds which are thus annually destroyed. If crows
or blackbirds are seen in numbers about cornfields, or if woodpeckers
are noticed at work in an orchard, it is perhaps not surprising that
they are accused of doing harm. Careful investigation, however, often
shows that they are actually destroying noxious insects; and also
that even those which do harm at one season may compensate for it by
eating insect pests at another. Insects are eaten at all times by the
majority of land birds. During the breeding season most kinds subsist
largely on this food, and rear their young exclusively upon it.
[Illustration: FIG. 323.--HEAD OF DUCK.]
[Illustration: FIG. 324.--JACANA. (Mexico, Southwest Texas, and
Florida.)
=Questions:= What appears to be the use of such long toes? What
peculiarity of wing? head?]
=Partridges.=--Speaking of 13 birds which he shot, Dr. Judd says:
These 13 had taken weed seed to the extent of 63 per cent of
their food. Thirty-eight per cent was ragweed, 2 per cent tick
trefoil, partridge pea, and locust seeds, and 23 per cent seeds of
miscellaneous weeds. About 14 per cent of the quail’s food for the
year consists of animal matter (insects and their allies). Prominent
among these are the Colorado potato beetle, the striped squash
beetle, the cottonboll-weevil, grasshoppers. As a weed destroyer the
quail has few, if any, superiors. Moreover, its habits are such that
it is almost constantly on the ground, where it is brought in close
contact with both weed seeds and ground-living insects. It is a good
ranger, and, if undisturbed, will patrol every day all the fields in
its vicinity as it searches for food.
[Illustration: FIG. 325.--NIGHTINGALE, × ¹⁄₃.
FIG. 326.--SKYLARK, × ¹⁄₃.
Two celebrated European songsters.]
=Doves.=--The food of the dove consists of seeds of weeds, together
with some grain. The examination of the contents of 237 stomachs
shows that over 99 per cent of the food consists wholly of vegetable
matter.
=Cuckoos.=--An examination of the stomachs of 46 black-billed
cuckoos, taken during the summer months, showed the remains of 906
caterpillars, 44 beetles, 96 grasshoppers, 100 sawflies, 30 stink
bugs, and 15 spiders. Of the yellow-billed cuckoos, or “rain-crow,”
109 stomachs collected from May to October, inclusive, were examined.
The contents consisted of 1,865 caterpillars, 93 beetles, 242
grasshoppers, 37 sawflies, 69 bugs, 6 flies, and 86 spiders.
[Illustration: FIG. 327.--LYRE BIRD, male.]
=Woodpeckers.=--Careful observers have noticed that, excepting a
single species, these birds rarely leave any conspicuous mark on a
healthy tree, except when it is affected by wood-boring larvæ, which
are accurately located, dislodged, and devoured by the woodpecker.
Of the flickers’ or yellow-hammers’ stomachs examined, three were
completely filled with ants. Two of the birds each contained more
than 3,000 ants, while the third bird contained fully 5,000. These
ants belong to species which live in the ground. It is these insects
for which the flicker is reaching when it runs about in the grass.
The yellow-bellied woodpecker or sapsucker (_Sphyrapicus varius_) was
shown to be guilty of pecking holes in the bark of various forest
trees, and sometimes in that of apple trees, and of drinking the
sap when the pits became filled. It has been proved, however, that
besides taking the sap the bird captures large numbers of insects
which are attracted by the sweet fluid, and that these form a very
considerable portion of its diet. The woodpeckers seem the only
agents which can successfully cope with certain insect enemies of
the forests, and, to some extent, with those of fruit trees also.
For this reason, if for no other, they should be protected in every
possible way.
[Illustration: FIG. 328.--SACRED IBIS. (Order?)]
=The night hawk, or “bull bat,”= may be seen most often soaring high
in air in the afternoon or early evening. It nests upon rocks or bare
knolls and flat city roofs. Its food consists of insects taken on the
wing; and so greedy is the bird that when food is plentiful, it fills
its stomach almost to bursting. Ants (except workers) have wings and
fly as they are preparing to propagate. In destroying ants night
hawks rank next to, or even with, the woodpeckers, the acknowledged
ant-eaters among birds.
[Illustration: FIG. 329.--TOP-KNOT QUAIL, or California Partridge.
(West Texas to California.)]
=The kingbird, or martin=, is largely insectivorous. In an
examination of 62 stomachs of this bird, great care was taken to
identify every insect or fragment that had any resemblance to a
honeybee; as a result, 30 honeybees were identified, of which 29 were
males or drones and 1 was a worker.
=Blue Jay.=--In an investigation of the food of the blue jay 300
stomachs were examined, which showed that animal matter comprised 24
per cent and vegetable matter 76 per cent of the bird’s diet. The
jay’s favorite food is mast (_i.e._ acorns, chestnuts, chinquapins,
etc.), which was found in 200 of the 300 stomachs, and amounted to
more than 42 per cent of the whole food.
[Illustration: FIG. 330.--PENGUIN OF PATAGONIA. Wings used as flippers
for swimming.]
=Crow.=--That he does pull up sprouting corn, destroy chickens, and
rob the nests of small birds has been repeatedly proved. Nor are
these all of his sins. He is known to eat frogs, toads, salamanders,
and some small snakes, all harmless creatures that do some good by
eating insects. Experience has shown that they may be prevented from
pulling up young corn by tarring the seed, which not only saves the
corn but forces them to turn their attention to insects. May beetles,
“dorbugs,” or June bugs, and others of the same family constitute the
principal food during spring and early summer, and are fed to the
young in immense quantities.
=Ricebird.=--The annual loss to rice growers on account of bobolinks
has been estimated at $2,000,000.
=Meadow Lark.=--Next to grasshoppers, beetles make up the most
important item of the meadow lark’s food, amounting to nearly 21 per
cent. May is the month when the dreaded cut-worm begins its deadly
career, and then the lark does some of its best work. Most of these
caterpillars are ground feeders, and are overlooked by birds which
habitually frequent trees, but the meadow lark finds and devours them
by thousands.
[Illustration: FIG. 331.--Umbrella holding the nests of social weaver
bird of Africa; polygamous.]
=Sparrows.=--Examination of many stomachs shows that in winter the
tree sparrow feeds entirely upon seeds of weeds. Probably each bird
consumes about one fourth of an ounce a day. Farther south the tree
sparrow is replaced in winter by the white-throated sparrow, the
white-crowned sparrow, the fox sparrow, the song sparrow, the field
sparrow, and several others; so that all over the land a vast number
of these seed eaters are at work during the colder months reducing
next year’s crop of worse than useless plants.
=Robin.=--An examination of 500 stomachs shows that over 42 per
cent of its food is animal matter, principally insects, while the
remainder is made up largely of small fruits or berries. Vegetable
food forms nearly 58 per cent of the stomach contents, over 47 per
cent being wild fruits, and only a little more than 4 per cent being
possibly cultivated varieties. Cultivated fruit amounting to about
25 per cent was found in the stomachs in June and July, but only a
trifle in August. Wild fruit, on the contrary, is eaten in every
month, and constitutes during half the year a staple food.
=Questions.=--Which of these birds are common in your neighborhood?
Which of them according to the foregoing report are plainly
injurious? Clearly beneficial? Doubtful? Which are great destroyers
of weed seeds? Wood-borers? Ants? Grain? Why is the destruction of
an ant by a night hawk of greater benefit than the destruction of an
ant by a woodpecker? Name the only woodpecker that injures trees.
If a bird eats two ounces of grain and one ounce of insects, has it
probably done more good or more evil?
[Illustration: FIG. 332.--AFRICAN OSTRICH, × ¹⁄₂₀. (Order?)]
CHAPTER XIV
MAMMALS (BEASTS AND MAN)
SUGGESTIONS.--A tame rabbit, a house cat, or a pet squirrel may be
taken to the school and observed by the class. Domestic animals may
be observed at home and on the street. A study of the teeth will
give a key to the life of the animal, and the teacher should collect
a few mammalian skulls as opportunities offer. The pupils should be
required to identify them by means of the chart of skulls (p. 194).
If some enthusiastic students fond of anatomy should dissect small
mammals, the specimens should be killed with chloroform, and the
directions for dissection usual in laboratory works on this subject
may be followed. There is a brief guide on page 223. The following
outline for the study of a live mammal will apply almost as well to
the rabbit or squirrel as to the cat.
=The Cat.=--The house cat (_Felis domestica_) is probably descended
from the Nubian cat (_Felis maniculata_, Fig. 333) found in Africa. The
wild species is about half again as large as the domestic cat, grayish
brown with darker stripes; the tail has dark rings. The lynx, or wild
cat of America (_Lynx rufus_), is quite different. Compare the figures
(333, 335) and state three obvious differences. To which American
species is the house cat closer akin, the lynx (Fig. 335) or the ocelot
(Fig. 334)? The domestic cat is found among all nations of the world.
What is concluded, as to its nearest relatives, from the fact that the
Indians had no cats when America was discovered? It was considered
sacred by the ancient Egyptians, and after death its body was embalmed.
The =body of the cat= is very flexible. It may be divided into five
regions, the head, neck, trunk, tail, and limbs. Its eyes have the
same parts as the eyes of other mammals. Which part of its eye is most
peculiar? (Fig. 333.) What part is lacking that is present in birds?
How are the eyes especially adapted for seeing at night? Does the pupil
in the light extend up or down or across the iris? Does it ever become
round?
[Illustration: FIG. 333.--WILD CAT OF AFRICA (_Felis maniculata_), ×
¹⁄₈.]
What is the shape and position of the _ears_? Are they large or small
compared with those of most mammals? They are fitted best for catching
sound from what direction? What is thus indicated in regard to the
cat’s habits? (Compare with ears of rabbit.) Touch the _whiskers_ of
the cat. What result? Was it voluntary or involuntary motion? Are the
_nostrils_ relatively large or small compared with those of a cow? Of
man?
Is the _neck_ long or short? Animals that have long fore legs usually
have what kind of a neck? Those with short legs? Why? How many _toes_
on a fore foot? Hind foot? Why is this arrangement better than the
reverse? Some mammals are sole walkers (_plantigrade_), some are toe
walkers (_digitigrade_). To which kind does the cat belong? Does it
walk on the ends of the toes? Does it walk with all the joints of the
toes on the ground? Where is the _heel_ of the cat? (Fig. 334.) The
_wrist_? To make sure of the location of the wrist, begin above: find
the shoulder blade, the upper arm (one or two bones?), the lower arm
(one or two bones?), the wrist, the palm, and the fingers (Fig. 337).
Is the heel bone prominent or small?
[Illustration: FIG. 334.--OCELOT (_Felis pardalis_), of Texas and
Mexico, × ¹⁄₉.]
In what direction does the _knee_ of the cat point? The heel? The
elbow? The wrist? Compare the front and hind _leg_ in length;
straightness; heaviness; number and position of toes; sharpness of
the _claws_. What makes the _dog’s claws_ duller than a cat’s? What
differences in habit go with this? Judging from the toe that has become
useless on the fore foot of the cat, which toe is lacking in the hind
foot? Is it the cat’s thumb or little finger that does not touch the
ground? (Fig. 337.) Locate on your own hand the parts corresponding to
the pads on the forefoot of a cat. Of what use are soft pads on a cat’s
foot?
Some animals have short, soft =fur= and long, coarse over hair. Does
the cat have both? Is the cat’s fur soft or coarse? Does the fur have a
color near the skin different from that at the tip? Why is hair better
suited as a covering for the cat than feathers would be? Scales? Where
are long, stiff bristles found on the cat? Their length suggests that
they would be of what use to a cat in going through narrow places? Why
is it necessary for a cat to be noiseless in its movements?
[Illustration: FIG. 335.--LYNX (_Lynx rufus_). The “Bob-tailed cat”
(North America).]
Observe the =movements of the cat=.--Why cannot a cat come down a tall
tree head foremost? Did you ever see a cat catch a bird? How does a
cat approach its prey? Name a jumping insect that has long hind legs;
an amphibian; several mammals (Figs. 362, 374). Does a cat ever trot?
Gallop? Does a cat chase its prey? When does the cat move with its heel
on the ground? The claws of a cat are withdrawn by means of a tendon
(see Fig. 338). Does a cat seize its prey with its mouth or its feet?
How does a cat make the purring sound? (Do the lips move? The sides?)
How does a cat drink? Do a cat and dog drink exactly the same way? Is
the cat’s tongue rough or smooth? How is the tongue used in getting the
flesh off close to the bone? Can a cat clean a bone entirely of meat?
[Illustration: FIG. 336.--JAGUAR, of tropical America.]
In what state of development is a newly born kitten? With what does the
cat _nourish its young_? Name ten animals of various kinds whose young
are similarly nourished. What is this class of animals called? Why does
a cat bend its back when it is frightened or angry? Does _a cat or a
dog_ eat a greater variety of food? Which refuses to eat an animal
found dead? Will either bury food for future use? Which is sometimes
troublesome by digging holes in the garden? Explain this instinct.
Which lived a solitary life when wild? Which had a definite haunt, or
home? Why are dogs more sociable than cats? A dog is more devoted to
his master. Why? A cat is more devoted to its home, and will return
if carried away. Why? Why does a dog turn around before lying down?
(Consider its original environment.)
[Illustration: FIG. 337.--SKELETON OF CAT.]
=The Skeleton= (Fig. 337).--Compare the _spinal column_ of a cat in
form and flexibility with the spinal column of a fish, a snake, and a
bird.
The _skull_ is joined to the spinal column by two knobs (or _condyls_),
which fit into sockets in the first vertebra. Compare the jaws with
those of a bird and a reptile. There is a prominent ridge in the temple
to which the powerful chewing muscles are attached. There is also a
ridge at the back of the head where the muscles which support the head
are attached (Fig. 348).
[Illustration: FIG. 338.--CLAW OF CAT (1) retracted by ligament, and
(2) drawn down by muscle attached to lower tendon.]
Count the _ribs_. Are there more or fewer than in man? The breastbone
is in a number of parts, joined, like the vertebræ, by cartilages.
Compare it with a bird’s sternum; why the difference? The shoulder
girdle, by which the front legs are attached to the trunk, is hardly to
be called a girdle, as the collar bones (clavicles) are rudimentary.
(They often escape notice during dissection, being hidden by muscles.)
The shoulder blades, the other bones of this girdle, are large, but
relatively not so broad toward the dorsal edge as human shoulder
blades. The clavicles are tiny because they are useless. Why does the
cat not need as movable a shoulder as a man? The pelvic, or hip girdle,
to which the hind legs are attached, is a rigid girdle, completed
above by the spinal column, to which it is immovably joined. Thus the
powerful hind legs are joined to the most rigid portion of the trunk.
=Mammals.=--The cat belongs to the _class Mammalia_ or mammals. The
characteristics of the class are that the young are not hatched from
eggs, but _are born alive, and nourished with milk_ (hence have lips),
and the _skin is covered with hair_. The milk glands are situated
ventrally. The position of the class in the animal kingdom was shown
when the cow was classified (p. 9). Their care for the young, their
intelligence, and their ability to survive when in competition with
other animals, causes the mammals to be considered the highest class in
the animal kingdom.
According to these tests, what class of vertebrates should _rank next
to mammals_? Compare the heart, lungs, blood, and parental devotion of
these two highest classes of animals.
[Illustration: FIG. 339.--SKELETON OF LION (cat family).]
=The first mammals=, which were somewhat like small opossums, appeared
millions of years ago, when the world was inhabited by giant reptiles.
These reptiles occupied the water, the land, and the air, and their
great strength and ferocity would have prevented the mammals from
multiplying (for at first they were small and weak), but the mammals
carried their young in a pouch until able to care for themselves, while
the reptiles laid eggs and left them uncared for. The first mammals
used reptilian eggs for food, though they could not contend with the
great reptiles. Because birds and mammals are better parents than
reptiles, they have conquered the earth, and the reptiles have been
forced into subordination, and have become smaller and timid.
[Illustration: FIG. 340.--WALRUS (_Trichechus rosmarus_).]
=Classification of Mammals.=--Which two have the closest _resemblances_
in the following lists: Horse, cow, deer. Why? Cat, cow, bear. Why?
Monkey, man, sheep. Why? Rat, monkey, squirrel. Why? Giraffe, leopard,
camel. Why? Walrus, cat, cow. Why? Check the five mammals in the
following lists that form a group _resembling each other most closely_:
Lion, bear, pig, dog, squirrel, cat, camel, tiger, man. State your
reasons. Giraffe, leopard, deer, cow, rat, camel, hyena, horse, monkey.
State reasons.
[Illustration: FIG. 341.--WEASEL, in summer; in Canada in winter it is
all white but tip of tail.]
=Teeth and toes= are the basis for subdividing the class mammalia
into orders. Although the breathing, circulation, and internal organs
and processes are similar in all mammals, the external organs vary
greatly because of the varying environments of different species. The
internal structure enables us to place animals together which are
essentially alike; _e.g._ the whale and man are both mammals, since
they resemble in breathing, circulation, and multiplication of young.
The external organs guide us in separating the class into orders. The
teeth vary according to the food eaten. The feet vary according to
use in obtaining food or escaping from enemies. This will explain the
difference in the length of legs of lion and horse, and of the forms of
the teeth in cat and cow. Make a careful study of the teeth and limbs
as shown in the figures and in all specimens accessible. Write out the
dental formulas as indicated at the top of page 194. The numerals above
the line show the number of upper teeth; those below the line show the
number of lower teeth in one half of the jaw. They are designated as
follows: _I_, incisors; _C_, canine; _M_, molars. Multiplying by two
gives the total number. Which skulls in the chart have the largest
canines? Why? The smallest, or none at all? Why? Compare the molars
of the cow, the hog, and the dog. Explain their differences. In which
skulls are some of the molars lacking? Rudimentary? Why are the teeth
that do not touch usually much smaller than those that do?
[Illustration: FIG. 342.--FOOT OF BEAR (_Plantigrade_).]
[Illustration: FIG. 343.--POLAR BEAR (_Ursus maritimus_).]
KEY, OR TABLE, FOR CLASSIFYING MAMMALS (_class Mammalia_) INTO ORDERS
Orders
A₁ =Imperfect Mammals=, young hatched or
prematurely born
B₁ Jaws a birdlike beak, egg-laying _Mon′otremes_
B₂ Jaws not beaklike, young carried in
pouch _Marsu′pials_
A₂ =Perfect Mammals=, young not hatched, nor
prematurely born
{C₁ Front part of both jaws lack
{ teeth _Eden′tates_
{
B₁ {C₂ Teeth with sharp points for
_Digits { piercing shells of insects _Insect′ivors_
with {
claws_ {C₃ Canines very long, molars suited
{ for tearing _Car′nivors_
{
{C₄ Canines lacking, incisors very
{ large _Rodents_
B₂ {C₁ Head large; carnivorous _Ceta′ceans_
_Digits {
not {C₂ Head small; herbivorous _Sire′neans_
distinct_{
{C₁ Five toes, nose prolonged into a
{ snout _Proboscid′eans_
{
{C₂ Toes odd number, less than five _E′quines_ }
B₃ { }
_Digits {C₃ Toes even number, upper front }_Un-
with { teeth lacking, chew the cud _Ru′minants_ } gu-
nails or{ }lates_
hoofs_ {C₄ Toes even number, upper front }
{ teeth present, not cud-chewers _Swine_ }
{
{C₅ All limbs having hands _Quad′rumans_
{
{C₆ Two limbs having hands _Bi′mans_
=Exercise in Classification.=--Copy the following list, and by
reference to figures write the name of its order after each mammal:--
Ape (Figs. 405, 406)
Rabbit (Fig. 345)
Dog (Figs. 356, 408)
Hog (Figs. 357, 393)
Bat (Figs. 347, 370)
Cat (Figs. 337, 348)
Armadillo (Figs. 349, 365)
Cow (Figs. 344, 386)
Walrus (Fig. 340)
Monkey (Figs. 352, 401)
Horse (Figs. 355, 395)
Ant-eater (Figs. 354, 364)
Antelope (Fig. 391)
Mole (Figs. 367, 368)
Beaver (Figs. 372, 373)
Duckbill (Fig. 359)
Tapir (Fig. 384)
Dolphin (Figs. 379, 397)
Use chart of skulls and Figs. 381, 382, 395-400 in working out this
exercise.
=Chart of Mammalian Skulls (Illustrated Study)=
5 1 2
Man’s dental formula is (_M_ -, _C_ -, _I_ -)² = 32.
5 1 2
In like manner fill out formulas below:--
Cow (_M_ - _C_ - _I_ -)² = 32
Rabbit (_M_ - _C_ - _I_ -)² = 28
Walrus (_M_ - _C_ - _I_ -)² = 34
Bat (_M_ - _C_ - _I_ -)² = 34
Cat (_M_ - _C_ - _I_ -)² = 30
Armadillo (_M_ - _C_ - _I_ -)² = 28
Horse (_M_ - _C_ - _I_ -)² = 40
Whale (_M_ - _C_ - _I_ -)² = 0
Am. Monkey (_M_ - _C_ - _I_ -)² = 36
Sloth (_M_ - _C_ - _I_ -)² = 18
Ant-eater (_M_ - _C_ - _I_ -)² = 0
Dog (_M_ - _C_ - _I_ -)² = 42
Hog (_M_ - _C_ - _I_ -)² = 44
Sheep (_M_ - _C_ - _I_ -)² = 32
[Illustration: FIG. 344.--Skull and front of lower jaw of COW.]
[Illustration: FIG. 345.--RABBIT.
_A_, _B_, incisors; _C_, molars.]
[Illustration: FIG. 346.--WALRUS (see Fig. 341).]
[Illustration: FIG. 347.--BAT.]
[Illustration: FIG. 348.--CAT.]
=Chart of Mammalian Skulls=
[Illustration: FIG. 349.--ARMADILLO.]
[Illustration: FIG. 350.--HORSE (front of jaw).]
[Illustration: FIG. 351.--GREENLAND WHALE.]
[Illustration: FIG. 352.--AMERICAN MONKEY.]
[Illustration: FIG. 353.--SLOTH (Fig. 363).]
[Illustration: FIG. 354.--ANT-EATER (Fig. 364).]
[Illustration: FIG. 355.--HORSE.]
[Illustration: FIG. 356.--DOG. Upper (_A_) and lower (_B_) jaw.]
[Illustration: FIG. 357.--HOG.]
[Illustration: FIG. 358.--SHEEP.]
The =lowest order of mammals= contains only two species, the duckbill
and the porcupine ant-eater, both living in the Australian region. Do
you judge that the _duckbill_ of Tasmania (Fig. 359) lives chiefly in
water or on land? Why? Is it probably active or slow in movement? It
dabbles in mud and slime for worms and mussels, etc. How is it fitted
for doing this? Which feet are markedly webbed? How far does the web
extend? The web can be folded back when not in use. It lays two eggs
in a nest of grass at the end of a burrow. Trace resemblances and
differences between this animal and birds.
[Illustration: FIG. 359.--DUCKBILL (_Ornithorhynchus paradoxus_).]
[Illustration: FIG. 360.--SPINY ANT-EATER (_Echidna aculeata_). View of
under surface to show pouch. (After Haacke.)]
The _porcupine ant-eater_ has numerous quill-like spines (Fig. 360)
interspersed with its hairs. (Use?) Describe its claws. It has a long
prehensile tongue. It rolls into a ball when attacked. Compare its jaws
with a bird’s bill. It lays one egg, which is carried in a fold of
the skin until hatched. Since it is pouched it could be classed with
the pouched mammals (next order), but it is egg-laying. Suppose the
two animals in this order did not nourish their young with milk after
hatching, would they most resemble mammals, birds, or reptiles?
Write the name of this _order_. ____ (See Table, p. 193.) _Why_ do you
place them in this order (____)? (See p. 193.) The name of the order
comes from two Greek words meaning “one opening,” because the ducts
from the bladder and egg glands unite with the large intestine and form
a cloaca. What other classes of vertebrates are similar in this?
[Illustration: FIG. 361.--OPOSSUM (_Didelphys Virginianus_).]
=Pouched Mammals.=--These animals, like the last, are numerous in the
Australian region, but are also found in South America, thus indicating
that a bridge of land once connected the two regions. The _opossum_ is
the only species which has penetrated to North America (Fig. 361). Are
its jaws slender or short? What kinship is thus suggested? As shown by
its grinning, its lips are not well developed. Does this mean a low or
a well-developed mammal? Where does it have a thumb? (Fig. 361.) Does
the thumb have a nail? Is the tail hairy or bare? Why? Do you think it
prefers the ground or the trees? State two reasons for your answer.
It hides in a cave or bank or hollow tree all day, and seeks food at
night. Can it run fast on the ground? It feigns death when captured,
and watches for a chance for stealthy escape.
The _kangaroo_ (Fig. 362), like the opossum, gives birth to imperfectly
developed young. (Kinship with what classes is thus indicated?) After
birth, the young (about three fourths of an inch long) are carried in
a ventral pouch and suckled for seven or eight months. They begin to
reach down and nibble grass before leaving the pouch. Compare fore legs
with hind legs, front half of body with last half. Describe tail. What
is it used for when kangaroo is at rest? In jumping, would it be useful
for propelling and also for balancing the body? Describe hind and fore
feet. _Order_ ____. _Why?_ ____. See key, page 193.
[Illustration: FIG. 362.--GIANT KANGAROO.]
=Imperfectly Toothed Mammals.=--These animals live chiefly in South
America (sloth, armadillo, giant ant-eater) and Africa (pangolin). The
sloth (Fig. 363) eats leaves. Its movements are remarkably slow, and a
vegetable growth resembling moss often gives its hair a green color.
(What advantage?) How many toes has it? How are its nails suited to its
manner of living? Does it save exertion by hanging from the branches of
trees instead of walking upon them?
[Illustration: FIG. 363.--SLOTH of South America.]
[Illustration: FIG. 364.--GIANT ANT-EATER of South America. (See
Fig. 354.) Find evidences that the edentates are a degenerate order.
Describe another ant-eater (Fig. 360).]
Judging from the figures (363, 364, 365), are the members of this order
better suited for attack, active resistance, passive resistance, or
concealment when contending with other animals? The ant-eater’s claws
(Fig. 364) on the fore feet seem to be a hindrance in walking; for what
are they useful? Why are its jaws so slender? What is probably the
use of the enormous bushy tail? The nine-banded armadillo (Fig. 365)
lives in Mexico and Texas. It is omnivorous. To escape its enemies, it
burrows into the ground with surprising rapidity. If unable to escape
when pursued, its hard, stout tail and head are turned under to protect
the lower side of the body where there are no scales. The three-banded
species (Fig. 366) lives in Argentina. Compare the ears and tail of the
two species; give reasons for differences. Why are the eyes so small?
The claws so large? _Order_ ____. _Why?_ ____.
[Illustration: FIG. 365.--NINE-BANDED ARMADILLO of Texas and Mexico.
(_Dasypus novemcinctus._) It is increasing in numbers; it is very
useful, as it digs up and destroys insects. (See Fig. 349.)]
[Illustration: FIG. 366.--THREE-BANDED ARMADILLO (_Tolypeutes
tricinctus_).]
=Insect Eaters.=--The soft interior and crusty covering of insects
makes it unnecessary for animals that prey upon them to have
flat-topped teeth for grinding them to powder, or long cusps for
tearing them to pieces. The teeth of insect eaters, even the molars
(Fig. 368), have many sharp tubercles, or points, for holding insects
and piercing the crusty outer skeleton and reducing it to bits. As most
insects dig in the ground or fly in the air, we are not surprised to
learn that some insect-eating mammals (the bats) fly and others (the
moles) burrow. Are the members of this order friends or competitors of
man?
[Illustration: FIG. 367.--THE MOLE.]
[Illustration: FIG. 368.--SKELETON OF MOLE. (Shoulder blade is turned
upward.)]
Why does _the mole_ have very small eyes? Small ears? Compare the shape
of the body of a mole and a rat. What difference? Why? Compare the
front and the hind legs of a mole. Why are the hind legs so small and
weak? Bearing in mind that the body must be arranged for digging and
using narrow tunnels, study the skeleton (Fig. 368) in respect to the
following: Bones of arm (length and shape), fingers, claws, shoulder
bones, breastbone (why with ridge like a bird?), vertebræ (why are the
first two so large?), skull (shape). There are no eye sockets, but
there is a snout gristle; for the long, sensitive snout must serve in
place of the small and almost useless eyes hidden deep in the fur. Is
the fur sleek or rough? Why? Close or thin? It serves to keep the mole
clean. The muscles of neck, breast, and shoulders are very strong.
Why? The mole eats earthworms as well as insects. It injures plants by
breaking and drying out their roots. Experiments show that the Western
mole will eat moist grain, though it prefers insects. If a mole is
caught, repeat the experiment, making a careful record of the food
placed within its reach.
[Illustration: FIG. 369.--SKELETON OF BAT.]
As with the mole, the skeletal adaptations of _the bat_ are most
remarkable in the hand. How many fingers? (Fig. 369.) How many nails on
the hand? Use of nail when at rest? When creeping? (Fig. 369.) Instead
of feathers, the flying organs are made of a pair of extended folds
of the skin supported by elongated bones, which form a framework like
the ribs of an umbrella or a fan. How many digits are prolonged? Does
the fold of the skin extend to the hind legs? The tail? Are the finger
bones or the palm bones more prolonged to form the wing skeleton?
[Illustration: FIG. 370.--VAMPIRE (_Phyllostoma spectrum_) of South
America. × ¹⁄₆.]
The skin of the wing is rich in blood vessels and nerves, and serves,
by its sensitiveness to the slightest current of air, to guide the bat
in the thickest darkness. Would you judge that the bat has sharp sight?
Acute hearing?
The moles do not _hibernate_; the bats do. Give the reason for the
difference. If bats are aroused out of a trance-like condition in
winter, they may die of starvation. Why? The mother bat carries the
young about with her, since, unlike birds, she has no nest. How are the
young nourished? _Order_ ____. _Why?_ ____. (Key, p. 193.)
[Illustration: FIG. 371.--POUCHED GOPHER (_Geomys bursarius_) × ¹⁄₄, a
large, burrowing field rat, with cheek pouches for carrying grain.]
[Illustration: FIG. 372.--Hind foot _a_, fore foot _b_, tail _c_, of
BEAVER.]
[Illustration: FIG. 373.--BEAVER.]
[Illustration: FIG. 374.--POSITION OF LIMBS IN RABBIT.]
=The Gnawing Mammals.=--These animals form the most numerous order of
mammals. They _lack canine_ teeth. Inference? The incisors are four
in number in all species except the rabbits, which have six (see Fig.
345). They are readily recognized by their _large incisors_. These
teeth grow throughout life, and if they are not constantly worn away
by gnawing upon hard food, they become inconveniently long, and may
prevent closing of the mouth and cause starvation. The hard enamel
is all on the front surface, the dentine in the rear being softer;
hence the incisors sharpen themselves by use to a chisel-like edge.
The molars are set close together and have their upper surfaces level
with each other. The ridges on them run crosswise so as to form a
continuous filelike surface for reducing the food still finer after
it has been gnawed off (Fig. 345). The lower jaw fits into grooves in
place of sockets. This allows the jaw to work back and forth instead of
sidewise. The rabbits and some squirrels have a hare lip; _i.e._ the
upper lip is split. What advantage is this in eating? In England the
species that burrow are called rabbits; those that do not are called
hares.
Name six enemies of rabbits. Why does a rabbit usually sit motionless
unless approached very close? Do you usually see one before it dashes
off? A rabbit has from three to five litters of from three to six young
each year. Squirrels have fewer and smaller litters. Why must the
rabbit multiply more rapidly than the squirrel in order to survive?
English rabbits have increased in Australia until they are a plague.
Sheep raising is interfered with by the loss of grass. The Australians
now ship them to England in cold storage for food. Rabbits and most
rodents lead a watchful, timid, and alert life. An exception is the
porcupine, which, because of the defense of its barbed quills, is dull
and sluggish.
The common rodents are:--
squirrels
rabbits
rats
mice
beavers
muskrats
porcupines
guinea pig
pouched gopher
prairie dog
prairie squirrel
chipmunk
ground hog
field mouse
Which of the above rodents are commercially important? Which are
injurious to an important degree? Which have long tails? Why? Short
tails? Why? Long ears? Why? Short ears? Why? Which are aquatic? Which
dig or burrow? Which are largely nocturnal in habits? Which are
arboreal? Which are protected by coloration? Which escape by running?
By seeking holes?
=Economic Importance.=--Rabbits and squirrels destroy the eggs and
young of birds. Are rabbits useful? Do they destroy useful food? The
use of beaver and muskrat skins as furs will probably soon lead to
their extinction. Millions of rabbits’ skins are used annually, the
hair being made into felt hats. There are also millions of squirrel
skins used in the fur trade. The hairs of the tail are made into fine
paint brushes. The skins of common rats are used for the thumbs of kid
gloves. _Order_ ____. _Why?_ ____.
[Illustration: FIG. 375.--FLYING SQUIRREL (_Pteromys volucella_). ×
¹⁄₄.]
=Elephants.=--Elephants, strange to say, have several noteworthy
resemblances to rodents. Like them, elephants have no canine teeth;
their molar teeth are few, and marked by transverse ridges and the
incisors present are prominently developed (Figs. 376, 377). Instead
of four incisors, however, they have only two, the enormous tusks, for
there are no incisors in the lower jaw. Elephants and rodents both
subsist upon plant food. Both have peaceful dispositions, but one order
has found safety and ability to survive by attaining enormous size and
strength; the other (_e.g._ rats, squirrels) has found safety in small
size. Explain.
Suppose you were to observe an elephant for the first time, without
knowing any of its habits. How would you know that it does not eat
meat? That it does eat plant food? That it can defend itself? Why would
you make the mistake of thinking that it is very clumsy and stupid?
Why is its skin naked? Thick? Why must its legs be so straight? Why
must it have either a very long neck or a substitute for one? (Fig.
376.) Are the eyes large or small? The ears? The brain cavity? What
anatomical feature correlates with the long proboscis? Is the proboscis
a new organ not found in other animals, or is it a specialization of
one or more old ones? Reasons? What senses are especially active in the
proboscis? How is it used in drinking? In grasping? What evidence that
it is a development of the nose? The upper lip?
[Illustration: FIG. 376.--HEAD OF AFRICAN ELEPHANT.]
[Illustration: FIG. 377.--MOLAR TOOTH OF AFRICAN ELEPHANT.]
The tusks are of use in uprooting trees for their foliage and in
digging soft roots for food. Can the elephant graze? Why, or why
not? There is a finger-like projection on the end of the snout which
is useful in delicate manipulations. The feet have pads to prevent
jarring; the nails are short and hardly touch the ground. _Order_ ____.
_Why?_ ____. Key, page 193.
=Whales, Porpoises, Dolphins.=--As the absurd mistake is sometimes made
of confusing _whales_ with fish, the pupil may compare them in the
following respects: eggs, nourishment of young, fins, skin, eyes, size,
breathing, temperature, skeleton (Figs. 209, 379, and 397).
[Illustration: FIG. 378.--HARPOONING GREENLAND WHALE (see Fig. 351).]
_Porpoises and dolphins_, which are smaller species of whales, live
near the shore and eat fish. Explain the expression “blow like a
porpoise.” They do not exceed five or eight feet in length, while the
deep-sea whales are from thirty to seventy-five feet in length, being
by far the largest animals in the world. The size of the elephant is
limited by the weight that the bones and muscles support and move. The
whale’s size is not so limited.
The _whale_ bears one young (rarely twins) at a time. The mother
carefully attends the young for a long time. The _blubber_, or thick
layer of fat beneath the skin, serves to retain heat and keep the body
up to the usual temperature of mammals in spite of the cold water.
It also serves, along with the _immense lungs_, to give lightness to
the body. Why does a whale need large lungs? The _tail of a whale_ is
horizontal instead of vertical, that it may steer upward rapidly from
the depths when needing to breathe. The _teeth_ of some whales do not
cut the gum, but are reabsorbed and are replaced by horny plates of
“whalebone,” which act as strainers. Give evidence, from the flippers,
lungs, and other organs, that the whale is descended from a land
mammal (Fig. 397). Compare the whale with a typical land mammal, as
the dog, and enumerate the specializations of the whale for living in
water. What change took place in the general form of the body? It is
believed that on account of scarcity of food the land ancestors of the
whale, hundreds of thousands of years ago, took to living upon fish,
etc., and, gradually becoming swimmers and divers, lost the power of
locomotion on land. _Order_ ____. _Why?_ ____.
[Illustration: FIG. 379.--DOLPHIN.]
Elephants are rapidly becoming extinct because of the value of their
ivory tusks. Whales also furnish valuable products, but they will
probably exist much longer. Why?
The =manatees and dugongs= (sea cows) are a closely related order
living upon water plants, and hence living close to shore and in the
mouths of rivers. _Order_ ____. _Why?_ ____.
[Illustration: FIG. 380.--MANATEE, or sea cow; it lives near the shore
and eats seaweed. (Florida to Brazil.)]
=Hoofed Mammals.=--All the animals in this order walk on the tips of
their toes, which have been adapted to this use by the claws having
developed into _hoofs_. The order is subdivided into the _odd-toed_
(such as the horse with one toe and the rhinoceros with three) and the
_even-toed_ (as the ox with two toes and the pig with four). All the
even-toed forms except the pig and hippopotamus chew the cud and are
given the name of _ruminants_.
=Horse and Man Compared= (Figs. 381, 399).--To which finger and toe
on man’s hand and foot does the toe of a horse’s foot correspond? Has
the horse kneecaps? Is its heel bone large or small? Is the fetlock on
toe, instep, or ankle? Does the part of a horse’s hind leg that is most
elongated correspond to the thigh, calf, or foot in man? On the fore
leg, is the elongated part the upper arm, forearm, or hand? Does the
most elongated part of the fore foot correspond to the finger, palm, or
wrist? On the hind foot is it toe, instep, or ankle? Is the fetlock at
the toe, instep, or heel? (Fig. 385.) Is the hock at the toe, instep,
heel, or knee? _Order_ ____. _Why?_ ____.
[Illustration: FIG. 381.--Left leg of man, left hind leg of dog and
horse; homologous parts lettered alike.]
=Specializations of the Mammals.=--The early mammals, of which the
present marsupials are believed to be typical, had five toes provided
with claws. They were not very rapid in motion nor dangerous in fight,
and probably ate both animal and vegetable food.
[Illustration: FIG. 382.--SKELETONS OF FEET OF MAMMALS.
_P_, horse; _D_, dolphin; _E_, elephant; _A_, monkey; _T_, tiger; _O_,
aurochs; _F_, sloth; _M_, mole.
=Question:= Explain how each is adapted to its specialized function.]
According to the usual rule, they tended to increase faster than the
food supply, and there were continual contests for food. Those whose
claws and teeth were sharper drove the others from the food, or preyed
upon them. Thus the specialization into the bold flesh eating beasts
of prey and the timid vegetable feeders began. Which of the flesh
eaters has already been studied at length? The insectivora escaped
their enemies and found food by learning to burrow or fly. The rodents
accomplished the same result either by acquiring great agility in
climbing, or by living in holes, or by running. The proboscidians
acquired enormous size and strength. The hoofed animals found safety in
flight.
[Illustration: _Equus_
_Protohippus_
_Pliohippus_
_Miohippus_
_Mesohippus_
_Orohippus_
FIG. 383.--Feet of the ancestors of the horse.]
[Illustration: FIG. 384.--TAPIR OF SOUTH AMERICA (_Tapirus
americanus_). × ¹⁄₂₅.
=Questions:= How does it resemble an elephant? (Fig. 376.) A horse? (p.
210.)]
[Illustration: FIG. 385.--HORSE, descended from a small wild species
still found in Western Asia.]
=Ungulates=, as the horse, need no other protection than their great
speed, which is due to lengthening the bones of the legs and rising
upon the very tip of the largest toe, which, to support the weight,
developed an enormous toe-nail called a hoof. The cattle, not having
developed such speed as the horse, usually have horns for defense. If a
calf or cow bellows with distress, all the cattle in the neighborhood
rush to the rescue. This unselfish instinct to help others was an aid
to the survival of wild cattle living in regions infested with beasts
of prey. Which of Æsop’s fables is based upon this instinct? The habit
of rapid grazing and the correlated habit of chewing the cud were also
of great value, as it enabled cattle to obtain grass hurriedly and
retire to a safe place to chew it. Rudiments of the upper incisors
are present in the jaw of the calf, showing the descent from animals
which had a complete set of teeth. The rudiments are absorbed and the
upper jaw of the cow lacks incisors entirely, as they would be useless
because of the cow’s habit of seizing the grass with her rough tongue
and cutting it with the lower incisors as the head is jerked forward.
This is a more rapid way of eating than by biting. Which leaves the
grass shorter after grazing, a cow or a horse? Why? Grass is very slow
of digestion, and the ungulates have an alimentary canal twenty to
thirty times the length of the body. Thorough chewing is necessary for
such coarse food, and the ungulates which chew the cud (ruminants) are
able, by leisurely and thorough chewing, to make the best use of the
woody fiber (cellulose) which is the chief substance in their food.
[Illustration: FIG. 386.--SKELETON OF COW. Compare with horse (Fig.
395) as to legs, toes, tail, mane, dewlap, ears, body.]
=Ruminants= have four divisions to the stomach. Their food is first
swallowed into the roomy _paunch_ in which, as in the crop of a bird,
the bulky food is temporarily stored. It is not digested at all in the
paunch, but after being moistened, portions of it pass successively
into the _honeycomb_, which forms it into balls to be belched up and
ground by the large molars as the animal lies with eyes half closed
under the shade of a tree. It is then swallowed a second time and
is acted upon in the third division (or _manyplies_) and the fourth
division (or _reed_). Next it passes into the intestine. Why is the
paunch the largest compartment? In the figure do you recognize the
paunch by its size? The honeycomb by its lining? Why is it round? The
last two of the four divisions may be known by their direct connection
with the intestine.
[Illustration: FIG. 387.--Food traced through stomachs of cow. (Follow
arrows.)]
[Illustration: FIG. 388.--Section of cow’s stomachs. Identify each.
(See text.)]
[Illustration: FIG. 389.--OKAPI. This will probably prove to be the
last large mammal to be discovered by civilized man. It was found in
the forests of the Kongo in 1900.
=Questions:= It shows affinities (find them) with giraffe, deer, and
zebra. It is a ruminant ungulate (explain meaning--see text).]
The true _gastric juice_ is secreted only in the fourth stomach.
Since the cud or unchewed food is belched up in balls from the round
“honeycomb,” and since a ball of hair is sometimes found in the stomach
of ruminants, some ignorant people make the absurd mistake of calling
the ball of hair the cud. This ball accumulates in the paunch because
of the friendly custom cows have of combing each other’s hair with
their rough tongues, the hair sometimes being swallowed. Explain the
saying that if a cow stops chewing the cud she will die.
[Illustration: FIG. 390.--AFRICAN CAMEL (_Camelus dromedarius_).]
Does a cow’s lower jaw move sidewise or back and forth? Do the ridges
on the molars run sidewise or lengthwise? Is a cow’s horn hollow? Does
it have a bony core? (Fig. 344.)
[Illustration: FIG. 391.--PRONG-HORNED ANTELOPE (_Antelocarpa
Americana_). Western states.]
The permanent hollow horns of the cow and the solid deciduous horns of
the deer are typical of the two kinds of horns possessed by ruminants.
The prong-horned antelope (Fig. 391) of the United States, however, is
an intermediate form, as its horns are hollow, but are shed each year.
The hollow horns are a modification of hair. Do solid or hollow bones
branch? Which are possessed by both sexes? Which are pointed? Which
are better suited for fighting? Why would the deer have less need to
fight than the cattle? Deer are polygamous, and the males use their
horns mostly for fighting each other. The sharp hoofs of deer are also
dangerous weapons. The white-tail deer (probably the same species as
the Virginian red deer) is the most widely distributed of the American
deer. It keeps to the lowlands, while the black-tailed deer prefers a
hilly country. The moose, like the deer, browses on twigs and leaves.
The elk, like cattle, eats grass.
[Illustration: FIG. 392.--ROCKY MOUNTAIN SHEEP (_Ovis montana_). ×
¹⁄₂₄.]
The native sheep of America is the big horn, or Rocky Mountain sheep
(Fig. 392). The belief is false that they alight upon their horns
when jumping down precipices. They post sentinels and are very wary.
There is also a native goat, a white species, living high on the Rocky
Mountains near the snow. They are rather stupid animals. The bison once
roamed in herds of countless thousands, but, with the exception of a
few protected in parks, it is now extinct. Its shaggy hide was useful
to man in winter, so it has been well-nigh destroyed. For gain man
is led to exterminate elephants, seals, rodents, armadillos, whales,
birds, deer, mussels, lobsters, forests, etc.
[Illustration: FIG. 393.--PECCARY (_Dicotyles torquatus_) of Texas and
Mexico. × ¹⁄₁₂.]
Our only native hog is the peccary, found in Texas (Fig. 393). In
contrast with the heavy domestic hog, it is slender and active. It is
fearless, and its great tusks are dangerous weapons. The swine are the
only ungulates that are not strictly vegetable feeders. The habit of
fattening in summer was useful to wild hogs, since snow hid most of
their food in winter. The habit has been preserved under domestication.
Are the small toes of the hog useless? Are the “dew claws” of cattle
useless? Will they probably become larger or smaller? _Order?_
[Illustration: =Illustrated Study=
FIG. 394.--BIRD.
FIG. 395.--HORSE.
FIG. 396.--OX.
FIG. 397.--DOLPHIN.
FIG. 398.--FISH.]
[Illustration: =Illustrated Study=
FIG. 399.--MAN.
FIG. 400.--CHIMPANZEE. (See Fig. 406.)]
=Illustrated Study of Vertebrate Skeletons=: Taking man’s skeleton as
complete, which of these seven skeletons is most incomplete?
Regarding the fish skeleton as the original vertebrate skeleton, how
has it been modified for (1) walking, (2) walking on two legs, (3)
flying?
Which skeleton is probably a degenerate reversion to original type?
(p. 209.)
How is the horse specialized for speed?
Do all have tail vertebræ, or vertebræ beyond the hip bones? Does
each have shoulder blades?
Compare (1) fore limbs, (2) hind limbs, (3) jaws of the seven
skeletons. Which has relatively the shortest jaws? Why? What seems to
be the typical number of ribs? limbs? digits?
Does flipper of a dolphin have same bones as arm of a man?
How many thumbs has chimpanzee? Which is more specialized, the foot
of a man or a chimpanzee? Is the foot of a man or a chimpanzee better
suited for supporting weight? How does its construction fit it for
this?
Which has a better hand, a man or a chimpanzee? What is the
difference in their arms? Does difference in structure correspond to
difference in use?
Which of the seven skeletons bears the most complex breastbone?
Which skeleton bears no neck (or cervical) vertebræ? Which bears only
one?
Are all the classes of vertebrates represented in this chart? (p.
125.)
[Illustration: FIG. 401.--SACRED MONKEY OF INDIA (_Semnopithecus
entellus_). × ¹⁄₁₂.]
=Monkeys, Apes, and Man.=--Study the figures (399, 400); compare apes
and man and explain each of the differences in the following list: (1)
feet, three differences; (2) arms; (3) brain case; (4) jaws; (5) canine
teeth; (6) backbone; (7) distance between the eyes.
[Illustration: FIG. 402.--LEMUR (_Lemur Mongoz_). × ¹⁄₁₀. Which digit
bears a claw?]
_A hand_, unlike a foot, has one of the digits, called a thumb, placed
opposite the other four digits that it may be used in grasping.
Two-handed man and four-handed apes and monkeys are usually placed in
one order, the _Primates_, or in two orders (see table, page 193). The
lowest members of this order are the _lemurs_ of the old world. Because
of their hands and feet being true grasping organs, they are placed
among the primates, notwithstanding the long muzzle and expressionless,
foxlike face. (Fig. 402.) Next in order are the _tailed monkeys_, while
the _tailless apes_ are the highest next to man.
[Illustration: FIG. 403.--BROAD-NOSED MONKEY. × ¹⁄₁₀. America.]
[Illustration: FIG. 404.--NARROW-NOSED MONKEY. × ¹⁄₁₂. Old World.]
[Illustration: FIG. 405.--GORILLA. (Size of a man.)]
The _primates of the New World_ are all monkeys with long tails and
broad noses. They are found from Paraguay to Mexico. The _monkeys and
apes of the Old World_ have a _thin partition_ between the nostrils,
and are thus distinguished from the monkeys of the New World, which
have a _thicker partition_ and have a broader nose. (Figs. 403, 404.)
The monkeys of America all have _six molar teeth_ in each half jaw
(Fig. 352); the monkeys and apes of the Old World have thirty-two teeth
which agree both in number and arrangement with those of man.
Which of the primates figured in this book appear to have the arm
longer than the leg? Which have the eyes directed forward instead of
sideways, as with cats or dogs?
Nearly all the primates are _forest dwellers_, and inhabit warm
countries, where the boughs of trees are never covered with ice or
snow. Their _ability in climbing_ serves greatly to protect them from
beasts of prey. Many apes and monkeys are able to assume the upright
position in walking, but they touch the ground with their knuckles
every few steps to aid in preserving the balance.
[Illustration: FIG. 406.--CHIMPANZEE.]
The _Simians_ are the highest family of primates below man, and include
the gorilla, chimpanzee, orang, and gibbon. Some of the simians weave
together branches in the treetops to form a rude nest, and all are very
affectionate and devoted to their young. How are apes most readily
distinguished from monkeys? (Figs. 401, 406.)
The study of man as related to his environment will be taken up in
detail in the part called Human Biology. We will there examine the
effect upon man’s body of the rapid changes since emerging from
savagery that he has made in food eaten, air breathed, clothing, and
habits of life.
[Illustration: FIG. 407.--ANATOMY OF RABBIT.
_a_, incisor teeth;
_b_, _b′_, _b″_, salivary glands;
_k_, larynx;
_l_, windpipe;
_c_, gullet;
_d_, diaphragm (possessed only by mammals);
_e_, stomach;
_g_, small intestine;
_h_, _h′_, large intestine;
_f_, junction of small and large intestine;
_g_, _g′_, cæcum, or blind sac from _f_ (corresponds to the shrunken
rudimentary vermiform appendix in man);
_m_, carotid arteries;
_n_, heart;
_o_, aorta;
_p_, lungs;
_q_, end of sternum;
_r_, spleen;
_s_, kidney;
_t_, ureters (from kidney to bladder _v_).
2 brain of rabbit:
_a_, olfactory nerves;
_b_, cerebrum;
_c_, midbrain;
_d_, cerebellum.]
=Table for Review=
==============+=======+=======+=======+=======+=======+=======+=======
| FISH | FROG | TURTLE| BIRD | CAT | HORSE | MAN
--------------+-------+-------+-------+-------+-------+-------+-------
| | | | | | |
Names of limbs| | | | | | |
| | | | | | |
--------------+-------+-------+-------+-------+-------+-------+-------
| | | | | | |
Acutest sense | | | | | | |
| | | | | | |
--------------+-------+-------+-------+-------+-------+-------+-------
| | | | | | |
Digits on fore| | | | | | |
and hind limb | | | | | | |
| | | | | | |
--------------+-------+-------+-------+-------+-------+-------+-------
| | | | | | |
Locomotion | | | | | | |
| | | | | | |
--------------+-------+-------+-------+-------+-------+-------+-------
| | | | | | |
Kind of food | | | | | | |
| | | | | | |
--------------+-------+-------+-------+-------+-------+-------+-------
| | | | | | |
Care of young | | | | | | |
| | | | | | |
==============+=======+=======+=======+=======+=======+=======+=======
[Illustration:
St. Bernard
Eskimo
Poodle
Dachshund
German mastiff
English bloodhound
Pointer
Bulldog
Greyhound
Newfoundland
Shepherd
Spitz
FIG. 408.--ARTIFICIAL SELECTION. Its effects in causing varieties
in one species. Which of the dogs is specialized for speed? Driving
cattle? Stopping cattle? Trailing by scent? Finding game? Drawing
vehicles? Going into holes? House pet? Cold weather? In Mexico there
is a hairless dog specialized for hot climates. The widely differing
environments under various forms of domestication cause “sports” which
breeders are quick to take advantage of when wishing to develop new
varieties. Professor De Vries by cultivating American evening primroses
in Europe has shown that a sudden change of environment may cause not
only varieties but new species to arise.]
HUMAN BIOLOGY
CHAPTER I
INTRODUCTION
To which _branch_ of animals does man belong? To which _class_ and
_order_ in that branch? (Animal Biology, pages 125, 193.) There is no
other animal _species in the same genus or order_ with man. This shows
a wide _physical_ difference between man and other animals, but man’s
_mind_ isolates him among the other animals still more.
[Illustration: FIG. 1.--FACIAL ANGLES of Caucasian (nearly 90°) and
Ethiopian (about 70°). The angle between lines crossing at front of
upper jaw near base of nose, one line drawn from most prominent part of
forehead, the other through hole of ear.]
The human species is divided into =five varieties= or races: 1.
_Caucasian_ (Fig. 1). Skin fair, hair wavy, eyes oval. (Europe except
Finns and Lapps, Western Asia, America.) 2. _Mongolian._ Skin yellow,
hair straight and black, face flat, nose blunt, almond eyes. (Central
Asia, China, Japan, Lapps and Finns of Europe, Eskimos of North
America.) 3. _Americans._ Skin copper red, hair straight, nose straight
or arched. (North and South America.) 4. _Malay._ Skin brown, face
flat, hair black. (Australia and Islands of Pacific.) 5. _Ethiopian_
(Fig. 1). Skin dark, hair woolly, nose broad, lips thick, jaws and
teeth prominent, forehead retreating, great toe shorter than next toe
and separate. (Africa, America.)
There is a _struggle between the races_ for the possession of
different lands. The Caucasian is gaining in Australia, Africa, and
America. With difficulty the Mongolians are kept from the western
shores of America. The Ethiopian in America shows a lessened rate
of increase every decade; this may be due to the tendency of the
race to crowd into cities and the strain of suddenly changing from
jungle life in less than two centuries. _Civilization is a strain_
upon any race. It is destroying the American Indian. The Mongolian
and Caucasian survive civilization best, but insanity is increasing
rapidly among the latter.
[Illustration: FIG. 2.--INDIAN WEAPONS: LANCE AND ARROW HEADS. From a
bank of mussel shells (remains of savage feast) at Keyport, N.J.]
=Man’s Original Environment.=--Primitive man lived without the use
of fire or weapons other than sticks or stones. His _first home
was in the tropics_, where his needs were readily supplied, and
probably in Asia. Many nations have a tradition of a home in a
garden (Greek, _paradisos_). His food was chiefly _tree fruits and
nuts_. When because of crowding he left nature’s garden, he acquired
skill in _hunting and fishing_ and the use of fire that flesh might
supplement the meager fruits of colder climates. His weapons were
of rough (chipped) stone at first--_in the old stone age_. In this
age the mammoth lived. He learned to polish implements in the _new
stone age_. The Indians were in that stage when Columbus came to
America (Figs. 2, 3). The cultivation of grain and the domestication
of animals probably began in this age. The _bronze_ and _iron ages_
followed the stone age.
[Illustration: FIG. 3.--INDIAN TOMAHAWK. Polished Stone. Keyport, N.J.]
=The Reaction between Man and his Environment.=--The estimates by
various geologists of the time man has existed as a species vary from
20,000 to 200,000 years. The _active life out of doors_ which man led
for _ages_ (Fig. 4) _has thoroughly adapted_ his body _only for such
a life_. Now steam and other forces work for him, and his _muscles_
dwindle; his _lungs_ are seldom fully expanded, and the unused
portions become unsound; he lives in tight houses, and the impure
air makes his _blood_ impure and his _skin_ delicate; he eats _soft
concentrated_ food, and his _teeth_ decay and his too roomy _food
tube_ becomes sluggish. His _nerves and brain_ are fully active and
they become unsound from overwork and impure blood.[3]
[3] It has been prophesied that the future man will be a brownie-like
creature with near-sighted eyes, shrunken body, slim little legs
and arms, large hairless head, toothless gums, a stomach using only
predigested food, muscles suited only to push an electric button
or pull a lever, and mind very active. But this disregards the
indispensable need of a sound mind for a sound body. There cannot even
be a play of emotion without a change in the circulation.
[Illustration: FIG. 4.--PRIMITIVE MAN, showing clothing and weapons of
chase and war.]
=Degeneration of Unused Parts.=--Several facts just stated illustrate
the biological law that _disuse causes degeneration_.
=Man’s Modification of his Environment.=--The energy of the world,
whether of coal, waterfall, oil, forest, or rich soil, has the sun
as its source. _All of these are being destroyed by man_, often
with recklessness and wantonness. The promised land which “flowed
with milk and honey” is now almost a desert. Other examples are
Italy, Carthage, Spain. The destruction of forests causes floods
which wash away the soil. _It is estimated that there are only one
fourth as many song birds in the United States as there were fifteen
years ago._ Insects and weeds or deserts replace rich soil, noble
quadrupeds, singing birds, and stately trees. Many farmers, however,
preserve the fertility of the soil.
=To the erect posture= is due man’s free use of his hands and
the _coöperation of hands and senses_. This has given man his
intellectual development. The erect position has given greater
freedom to the chest. _Man uses fewer organs of locomotion than
any other animal._ The opossum has two hands, but they are on
the hind limbs. The ape has four hands, but must use them all in
locomotion. (What is a hand?) The erect position, however, makes
_spinal deformity_ easier to acquire, and the _whole weight being
upon one hip_ at each step man is liable to hip-joint diseases.
In the horizontal trunk the organs lie one behind another; in man
they _lie one upon another_, and are more liable to _crowding_ and
_displacement_. The prone position in sickness helps to restore
them. Large blood vessels at neck, armpits, and groins, which occupy
protected positions in quadrupeds, are _held to the front and
exposed_ to danger. The _open end_ of the vermiform appendix and
of the windpipe are _upward_ in the erect trunk of man. Valves are
lacking in some vertical veins and present where little needed in
horizontal veins. But the _freedom of the hands_ more than makes up
for all the disadvantages of erectness.
=The Survival of the Fittest.=--_Those who do not work degenerate._
Those who overwork, or work with only a few organs, as the brain and
nerves, degenerate. The workers survive and _increase in numbers_,
the idle perish and _leave few descendants_.
=What rate of adjustment to new environment= is possible for man? This
has not been ascertained; _it is probably much slower than has been
generally imagined_. The natives of Tasmania, New Zealand, and many
of the Pacific Islands became _extinct in less than a century_ after
adopting clothing and copying other habits from Europeans. Life in
the country in civilized lands differs less from the environment of
primitive man than does life in cities. Cities have been likened to
the lion’s cave in the fable, to which many tracks led, but from which
none led. _The care of health in cities_ is now making rapid strides
along the biological basis of purer air, more open space, less noise,
simple food, and pure water. Biology, by supplying as a standard
the conditions which molded man’s body for ages, furnishes a simple
and sure basis for hygiene. To mention one instance among many, man
blundered for centuries in attempting the cure of consumption, and
well-nigh gave up in despair. Yet it has recently been shown that if
the sufferer returns only in a measure to the open-air habits of his
remote ancestors, tuberculosis is one of the most curable of diseases.
The biological guide to health is surer and simpler than tinkering with
drugs, fussing with dietetics, and avoiding exposure. _Man is of all
animals least thoroughly adjusted to his environment_, because of his
continual and rapid progress. _Disease_ may be defined as the _process
by which the body adapts_, or attempts to adapt, _itself to_ so sudden
a _change of environment_ that some organ has failed to work in harmony
with the others. By disease the body comes into adjustment with the new
condition, or attempts to do so.
=Protoplasm.=--The life and growth of man’s body, as the life and
growth of all animals and plants, depend upon the activity of the
living substance called _protoplasm_, as manifested in minute bodies
called _cells_. In fact, protoplasm cannot exist outside of cells. The
cells of the human body and their relation to the body as a whole will
next be considered.
[Illustration: FIG. 5.--AN AMEBA, highly magnified. _nu_, nucleus;
_psd_, false foot.]
=The Ameba.=--Of all the animal kingdom, the _minute creatures that
can be seen only with a microscope_ are most different from man. One
of the most interesting of these is the _a-me′ba_ (Fig. 5; spelled
also _amœba_, see Animal Biology, Chap. II). _A thousand of them
placed in a row would hardly reach an inch._ Some may doubt whether
the ameba is a complete animal. Study the figures of it, and no head,
or arms, or legs, or mouth can be found. It appears, when still, to
be merely a _lump of jelly_. But the ameba can _push out any part
of its body as a foot_, and move slowly by rolling its body into
the foot. _It can put out any part of its body as an arm_, and take
in a speck of food; or, if the food happens to be near, the ameba
can _make a mouth in any part of its body_, and swallow the food by
closing around it (Animal Biology, Fig. 12). The ameba has no lungs,
but _breathes with all the surface of its body_. Any part of its body
can do anything that another part can do. When the ameba grows to a
certain size, it multiplies by squeezing together near the middle
(Animal Biology, Fig. 13) _and dividing into two parts_. Amebas have
not been observed to die of old age; starvation and accident aside,
they are immortal.