CHAPTER XI. MOSSES, MUSHROOMS, AND MOULDS.

40. LIVERWORTS AND TRUE MOSSES.

1. =A common liverwort.=—Look along the sides of a brook or a well,

and try to find a flat green plant with numerous lobed and overlapping

branches. Each branch is perhaps half an inch across. This is one

of the commonest liverworts (_Pellia_). Notice the prominent midrib

running along each branch. In spring, observe the “frilled” appearance

of the end, caused by the small new branches.

Pull the plant up, and notice that it is attached to the soil by a

large number of fine _hairs_ which spring from the lower surface of the

midrib.

In February, or March, examine the upper surface of the growing plant

with a lens, and notice the small, dark-green balls, mounted on short,

thick stalks. Examine these at intervals until May, and notice that the

stalks then grow rapidly until they are two or three inches long. Each

is white, and still bears the black ball (the _capsule_) on its summit.

When the stalk is full-grown, the capsule opens—its wall splitting into

four parts—to liberate the _spores_. How soon, after the liberation of

the spores, do the capsule and its stalk die down?

2. =A common moss.=—Separate a single plant from a tuft of the common

moss (_Funaria_) which grows, almost everywhere, on the ground and on

walls. Notice that the plant consists of a _stem_ perhaps half an inch

high, thickly covered with small simple green _leaves_. The moss is

fixed in the soil by a tuft of fine _hairs_.

On some of the plants notice a thin stalk (about half an inch long)

springing from the top of the stem; and on the end of the stalk an

ovoid _capsule_ or spore-box. In cases where the stalk is not yet

full-grown, notice that the capsule is covered by a conical _hood_,

somewhat like a candle-extinguisher.

Select a plant bearing a ripe capsule, and warm it gently before the

fire—holding it over a sheet of paper—to dry it. Examine the mouth of

the capsule with a lens, and try to see the teeth which surround the

opening. Then shake the capsule over moist soil in a small flower-pot

to scatter the _spores_; cover with a sheet of glass and keep in a warm

room. In a few days notice that the soil is covered with fine green

threads. Ultimately new moss plants will grow from these.

=The life-history of a liverwort.=—One of the commonest and simplest

of this class of plants is known to botanists as _Pellia_. It may

generally be found growing by the sides of streams or old wells. It

has neither stem, leaves, nor root, but consists of flat, green,

overlapping lobes which fork at their ends. It branches very freely,

and in spring the new branches give the ends of the lobes a frilled

appearance. A rather prominent midrib runs along each branch. The plant

is attached to the soil by a large number of fine hairs which spring

from the lower surface of the midrib.

The whole appearance of this liverwort is very suggestive of the

prothallus (Fig. 147) of a fern; and, indeed, it corresponds to a

prothallus, not only in its general structure and mode of life, but

also in bearing sexual organs of a very similar type. It was seen in

Chapter X. that a fern prothallus at length produces an embryo, which

grows up and forms the spore-bearing generation which is what people

usually understand by a “fern”.

The liverwort also gives rise to a spore-bearing generation, but in

this case it consists merely of a small, round, spore-box, dark-green

in colour, which is carried on the summit of a white stalk—the whole

looking somewhat like a stout pin. In February, or early March, the

spore-boxes may be seen upon the upper surface of the plant as small

balls, perhaps one-sixteenth of an inch in diameter, protruding from

the mouth of a little pocket in which their early stages are passed.

About May, their stalks lengthen so rapidly that in a few days the

spore-boxes are lifted to a height of two or three inches. Then each

box opens by its wall splitting into four, and the spores are liberated

to germinate and form new liverworts. Having thus shed the spores, the

box and stalk die down.

The complete life-cycle of a liverwort thus includes two unlike

generations, as that of a fern does; but it is a different generation

which attains the greater development in the two cases. The ordinary

fern is the spore-bearing generation; the “ordinary” liverwort is the

sexual generation, and its sporing offspring is not a separate plant at

all, but a mere stalked box, almost entirely dependent upon its parent.

[Illustration: FIG. 156.—A Moss. _A_, a plant with spore-case still

covered by hood (_c_) (× 1). _B_, a plant with ripe spore-case (_k_);

_s_, stalk; _d_, lid; _rh_, hairs (× 1). _C_, mature spore-case with

lid (_d_) removed; _p_, fringe of teeth (× 3).]

=The mosses.=—A moss-plant appears at first sight to be very similar

in its general features to one of the higher plants; for it has a

little stem, bearing flattened green leaves which build up carbonaceous

food in the usual way. It has no true roots, but fine hairs penetrate

the soil and do the work of roots by taking up solutions of mineral

food. It is all the more remarkable, therefore, to find from its

method of reproduction that the moss-plant belongs to the generation

which corresponds to the prothallus stage of a fern’s life-history,

and not to the leafy, sporing generation which it somewhat resembles

superficially.

The sexual organs of a moss are essentially of the same type as those

which a prothallus bears, and here also the tiny male cells gain access

to the female cells by swimming through a drop of rain or dew. The

result of fertilisation is an embryo which, however, grows up to form,

not a plant with stem and leaves, but a stalked spore-case only.

In a tuft of the moss _Funaria_, which is so common in all country

places, several stages of development of the spore-cases may usually

be seen. Fig. 156 represents a moss which is very similar to _Funaria_

but larger. In _A_, the spore-case is still covered by a conical

hood (_c_). In _B_, the stalk (_s_) has grown much longer, and the

hood has dropped off. The spore-case or capsule (_k_) is now seen to

be a pear-shaped body, closed by the lid (_d_). When the spores are

ripe, the lid becomes detached. The mouth of the nodding capsule is

still blocked, however, by a number of teeth (Fig. 156, _C_, _p_)

which remain close together in damp weather. In dry weather the teeth

separate, and allow the spores to fall out. When a moss spore falls in

a favourable situation it germinates to form a fine, branching network

of green threads, from which new moss-plants arise as buds.

The obvious plant of a moss—like that of a liverwort—therefore

corresponds to the prothallus generation of a fern or horsetail.

Its sporing generation, corresponding to the obvious fern-plant or

horsetail, is a stalked spore-case, which is always more or less

dependent on its parent and dies down as soon as its work of scattering

the spores is accomplished.

41. THE COMMON MUSHROOM.

1. =Habit of growth.=—In what situations do you find mushrooms growing?

In what kinds of weather and at what time of the year are they most

abundant? Take up a mushroom with a trowel, and carefully wash the

earth from the lower part to see the tangle of white threads (called

the _mycelium_), which is the underground part of the plant. See that

several of these run into the bottom of the stalk. On the underground

mycelium look for young mushrooms in the “button” stage. Look around,

and try to get a series of mushrooms showing all stages from the

smallest buttons to fully-opened specimens.

2. =Structure.=—Draw a side view (natural size) of a full-grown

mushroom, showing the _stalk_ and _cap_. Running round the stalk notice

a ragged flap, called the _collar_. What is the height of the collar

from the base of the stalk? Examine younger mushrooms to find what

the collar really is. Notice that in young specimens a membrane or

_veil_ stretches from the edge of the cap to the stalk, and that as

the mushroom grows larger this veil is torn away from the cap (Fig.

157), and remains as a ragged flap (the collar) on the stalk. In young

specimens, therefore, the lower side of the cap is completely shut in

by the veil, while in fully-grown ones it is exposed.

3. =The gills and spores.=—Cut the stalk across at the top, and make a

drawing of the lower surface of the cap. Notice the radiating vertical

plates (the _gills_), and their flesh-coloured or dark-brown tint. Be

careful to show the exact arrangement of the gills in, say, a quarter

of the drawing. Cut off the cap of a mushroom which has brown gills

and lay it, gills down, on a sheet of paper; cover it with a tumbler

to shield it from draughts, and leave it for a day. Then take off the

cap (being careful not to smear it along the paper), and observe the

radiating brown lines. On touching them, it will be seen that the

lines consist of fine brown dust. The particles of dust are _spores_.

They have evidently fallen from the gills.

4. =The source of the mushroom’s food.=—What is the colour of the

mushroom? Cut through the stalk and cap in various directions and

notice the pure white “flesh” of the interior. Do you think it likely

that the plant can obtain carbonaceous food from the air? Why not?

Dry a mushroom and burn it carefully. Does it contain _carbon_? Where

must the carbon have come from, if not from the air. Can you find any

decaying vegetable or animal matter in the soil in which mushrooms grow?

5. =Toadstools.=—Carefully compare the common mushroom with other

gilled fungi which look somewhat like it. Notice particularly the

following characters: the colour, shape, and texture of the surface of

the cap; the colour and arrangement of the gills; the proportions of

the length and thickness of the stalk to the diameter of the cap; the

presence or absence of a collar on the stalk; the presence or absence

of a cup, or scaly swelling, at the base of the stalk.

The following =precautions= are necessary in selecting mushrooms for

food: Never eat a “button” mushroom; in this stage wholesome and

poisonous mushrooms cannot be properly distinguished from each other.

Reject all mushrooms which show signs of a _cup_ or a scaly swelling at

the base of the stalk—especially if they have also _white spores_ and a

collar.

=The common meadow mushroom.=—The common mushroom (Fig. 157) may easily

be found in meadows, especially in autumn and after damp weather

in summer. The part which rises above the surface of the ground

consists of a stout =stalk=, about three inches long and perhaps

three-quarters of an inch thick. On the upper end of the stalk is a

circular horizontal =cap=, convex and smooth above and concave below;

with a diameter about equal to the length of the stalk. The interior

of the stalk and cap is composed of a firm white fleshy substance.

The underground part of the plant consists of a tangle of fine white

threads, most of which are woven together into strands; and it is easy

to see that several of these strands run into the base of the stalk.

Each of the fine threads is called a =hypha=, and the network which

they together compose is known as the =mycelium=. It has indeed been

found by microscopic examination that the whole plant is built up of

such hyphae—closely packed together in the stem and cap, more loosely

aggregated in the underground strands. The stalk of the full-grown

mushroom bears, a little above its middle, a ragged ring of tissue—the

=collar=. This ring is the remains of a membrane or =veil= which in the

younger stages reached to the edge of the cap, completely enclosing its

lower surface; but which was torn off the cap (Fig. 157) as the stalk

of the “button” mushroom elongated.

[Illustration: FIG. 157.—Common Meadow Mushroom. To the right, mushroom

in “button” stage (× ½).]

=The reproduction of the mushroom.=—The lower side of the cap of a

mature mushroom bears a very large number of radiating plates called

the =gills=. These are at first pink, but the colour afterwards changes

to a dark brown. Each gill produces an immense number of extremely fine

=spores=, too small to be seen individually by the naked eye. When,

however, the cap of a mushroom is laid, gills down, on a sheet of paper

and protected from draughts, a “spore print” is obtained; the dust of

the fallen spores marks the positions of the gills in brown radial

lines. Quite recently it has been found possible to raise new mushroom

plants by germinating the spores, and there can be no doubt that this

is the natural method of reproduction.

=The method of life of the mushroom.=—The mushroom, like all the

plants we have studied, thus consists of parts which perform one or

other of two duties; that of feeding the plant, and that of continuing

the race. In this case the food is supplied _entirely_ by the

underground mycelium; while the aërial part, consisting of stalk and

cap, is concerned only with the work of scattering the spores. There is

nothing corresponding to the leaf-green of the higher plants, and the

mushroom is therefore unable to make use of the carbon dioxide of the

air (p. 34) as the source of the carbonaceous food which is necessary

for its life. Carbonaceous and mineral food alike are obtained from the

soil by the underground mycelium. The plant is, in short, dependent

upon carbonaceous food which has been previously built up by some

other plant or animal, and can therefore grow only in soil containing

decaying animal or vegetable matter. It would be quite unable to

subsist upon the nutritive solution of salts which was seen (p. 29) to

suffice (when supplemented by fresh air) for green plants.

=Fungi.=—The mushroom belongs to a class of plants called the Fungi,

all of which obtain their carbonaceous food ready-made from some

other plant or animal, living or dead. For this reason many fungi are

parasitic upon other living plants. Most of the diseases of crops and

of forest trees are due to fungi. The moulds which destroy food are

fungi, and the dry rot which ruins timber is caused by organisms of the

same class.

=Toadstools.=—The common meadow mushroom is a justly-esteemed article

of food, but some other gilled fungi, which are intensely =poisonous=,

bear a sufficiently close resemblance to mushrooms to render them

dangerous. The student should therefore take every opportunity of

examining these, and of comparing them with the edible mushroom in the

manner described on p. 204.

42. MOULDS.

1. =The growth of moulds.=—Damp three small slices of bread, and cover

them with tumblers to prevent them from drying. Expose one slice to

ordinary daylight; keep another in a dark place at about the same

temperature; and submit the third to the direct rays of bright sunlight

as much as possible.

2. =White mould= (_Mucor_).—In one or two days observe that the bread

is covered with white fleecy threads. Some of these may grow to a

height of an inch or more, and end in small black knobs which can be

seen with the naked eye. The knobs contain _spores_. Examine the mould

with the help of a lens. On which of the three pieces of bread is there

most mould, and on which the least?

Mix freshly-boiled and strained juice of stewed fruit (preferably

colourless or nearly so) with an equal quantity of water. Half fill a

small glass with the mixture, and with the point of a needle add a few

spores from the mould on the bread. Cover the glass, avoid shaking it,

and examine day by day. Notice the delicate threads (_hyphae_) of the

_mycelium_ which spreads over the liquid and sends down branches below

the surface. Observe also the hyphae which grow up into the air and

bear spore-knobs at the end. Similarly, sow some of the spores on a

little of the nutritive solution of salts (p. 27) contained in a clean

glass. Do these spores also develop into moulds? Why not?

Scratch through the skin of a ripe fruit (_e.g._ plum, apple, grape,

etc.) with a needle, and lay the fruit aside with the scratch upward.

Scratch a similar fruit in the same way, and rub into the scratch a few

mould-spores before laying it aside. With these put a third fruit which

has a perfectly whole skin. Compare the fruits after a few days.

3. =Blue mould= (_Penicillium_).—After some days the white mould on the

bread will probably be crowded out by a blue or greenish velvety mould

called _Penicillium_. Examine it with a lens. As with _Mucor_, make

experiments as to the action of light upon this mould; the germination

of its spores (which form a greenish powder on the ends of the short

aërial hyphae) in fruit-juice; and the action of the spores upon ripe

fruits.

=Common moulds.=—In the dust floating about in the air the spores of

certain moulds are almost always present. When these spores fall upon

materials which—like bread, fruit, old leather, etc.—are capable of

affording them suitable food-substances, they germinate and form the

woolly growths which are familiar to everyone.

=The white mould= (_Mucor_).—What is known familiarly as white mould,

and botanically as =Mucor=, is very convenient for study on account of

its abundance and large size. If a piece of bread is kept in a damp

atmosphere it generally becomes covered, after a day or two, with a

fleecy growth of the white threads of this mould. These may attain

a height of an inch or more, and many of them bear at their ends a

small black knob, in which the spores are formed. When mature, the

knobs burst open, and the fine spores are scattered in the air. The

various parts of the mould are best seen in position by scattering

some of the spores, or a little dust from a shelf, upon the surface

of clear, colourless fruit-juice in a glass vessel, and following the

stages of growth with a lens. It then becomes clear that the mould—like

the mushroom—consists of (_a_) a buried tangle or mycelium of hyphal

threads which take in the plant’s food, and of (_b_) an aërial part

which scatters the spores. The mould also resembles the mushroom in not

containing the green colouring matter possessed by the higher plants,

and therefore in being dependent upon ready-made organic food. Provided

with this, it can grow freely even in the dark.

[Illustration: FIG. 158.—_Penicillium._ An aërial hypha with its

terminal spore-brushes. (× 360).]

=Blue mould= (_Penicillium_).—It is generally found that the fleecy

hyphae of _Mucor_, which first cover the damp bread, are crowded out

in a short time by the growth of another mould, which is known to

botanists as =Penicillium=. This also consists of a mycelium, which

penetrates the nutritive substance, and of aërial hyphae which produce

spores. Here, however, the spores are not borne in cases, but break off

from the ends of brush-like branches of the aërial hyphae (Fig. 158).

The spores of _Penicillium_ are greenish-blue in colour, and it is from

this circumstance that the mould receives its common name. The colour

is, however, quite different from the leaf-green which gives the higher

plants the power, in sunlight, of decomposing the carbon dioxide of the

air and building up their own carbonaceous food—a power which neither

_Penicillium_ nor any other fungus possesses.

=The smallest plants.=—The description of microscopic organisms is

beyond the scope of this book, but the student ought to realise that

by far the greater number of plants are quite invisible to the naked

eye. Some of these—to be found in every pond and ditch—are green, and,

though they are of very simple structure, they obtain their food in

a manner substantially resembling that adopted by a flowering-plant

or a fern. Others, like the yeast plant, are fungi, and are subject

to the limitations in food-supply which are characteristic of that

class. The smallest of all plants are the =bacteria=; they are almost

inconceivably minute, yet they possess an influence upon the health and

wellbeing of mankind which it is impossible to over-estimate.

EXERCISES ON CHAPTER XI.

1. Explain in what respects a moss plant resembles and

differs from the prothallus of a fern.

2. What structure in a moss corresponds, as regards

reproduction, to an ordinary fern plant?

3. What do you mean by the term “alternation of

generations”? Explain your answer by references to ferns

and mosses.

4. How does a mushroom resemble and differ from a green

plant in its method of obtaining food?

5. Why does a piece of damp bread become mouldy when it is

exposed to the air?

6. Describe simple experiments which prove that the dust of

ordinary air contains living particles.

7. Mention common plants which are wafted about by currents

of air in a dwelling-house, and point out changes which

such plants may set up in articles of human food. (1905)

_PART II._ ANIMAL LIFE

CHAPTER XII. THE RABBIT: A TYPICAL MAMMAL.

43. THE RABBIT: HABITS AND APPEARANCE.

1. =The habits of the wild rabbit.=—In what places have you known

wild rabbits to have a _warren_? In what kind of ground is a rabbit

warren generally found? How can you recognise it? Are all the holes

of the warren of similar size, or can you distinguish between main

entrances and “bolt-holes”? Look for smooth paths, perhaps nine inches

wide, which lead to the main entrances and intersect each other, so

as to form “runs.” Watch the animals feeding and playing; to do this

successfully it will be necessary to keep very still and silent; avoid

walking on the runs. What do the rabbits eat? Do they walk, or hop?

How do they run? Notice how conspicuous is the white tail of a running

rabbit. In June look for a nest of young rabbits. The position of such

a nest may often be recognised, when the doe is away from home, by a

smooth patch of earth with which she has covered up the hole. Dig up

this very carefully and notice how the nest is lined. Examine the young

ones without hurting them, and then cover them up again.

What is the _colour_ of a wild rabbit? Does the colour render the

animal less conspicuous? Are tame rabbits so often of this colour? Why

not? Watch a tame rabbit, noticing especially the movements of its

nostrils, whiskers, and ears, and its method of feeding. Try to see how

it gnaws the bars of its hutch.

2. =Fur.=—Examine a dead rabbit. With what is the skin covered? What

are the differences between the fur of a rabbit, the hair of a dog,

and the wool of a sheep? Is fur curly? Does it lie flat on the skin?

Does it consist of different sizes of hair—short, fine hairs and long,

thicker ones? What other animals do you know which have fur?

3. =The head.=—(_a_) _The whiskers._—On what parts of the head are

the longest hairs found? How do these differ, apart from length, from

ordinary hairs? What other common animals have whiskers? Do such

animals often make their way through narrow passages? What do you

suppose is the use of the whiskers?

(_b_) _The skull._—Feel the bones of the head through the skin, and

make out the rounded brain-case, the ridge above and the arch below

each eye, and the positions of the jaws.

(_c_) _The external ears._—Examine the large ear-flaps. Notice that the

upper parts are thin and almost transparent, and that the lower parts

are gristly and lead into the interior of the head.

(_d_) _The eyes._—Notice that the eyes are at the _sides_ of the head.

Is this position an advantage to the rabbit? Examine, in each eye,

the upper and lower lids; and also, in the angle of the eye next the

nose, the _third eyelid_—a fold of white skin. Take hold of this fold

with the forceps and see that it is easily pulled over the eyeball.

Look in a mirror and see the little fleshy body which occupies a

similar position in your own eye; this corresponds to the rabbit’s

third eyelid. In the visible part of the rabbit’s eyeball notice the

round dark _pupil_ in the middle (contrast the pupil of a cat’s eye);

the coloured ring (the _iris_) surrounding the pupil; and the “white”

(called the _sclerotic_) surrounding the iris.

(_e_) _The lips and nostrils._—Notice how the upper lip is split in

the middle line, so as to show the front teeth. What is the use of the

split? Notice the grooves passing from the upper lip to the nostrils.

(_f_) _The inside of the mouth._—Open the rabbit’s mouth and notice:

(i) The two gnawing or _incisor teeth_ in the lower jaw, and the pair

of strongly-grooved incisors which are so conspicuous in the upper jaw.

Just behind the large, upper incisors two smaller incisors may be felt

with the finger. Separated by a wide space from the incisors are the

_grinding teeth_—six on each side in the upper jaw, and five on each

side in the lower jaw.

(ii) The _tongue_, lying between the halves of the lower jaw.

(iii) The hard _ridges_ running across the fore half of the roof of the

mouth.

(iv) The _hairiness_ of the inside of each cheek, between the incisor

and grinding teeth.

4. =The neck.=—Notice how the neck enables the head to be turned freely

in various directions without the body being moved. Feel through the

skin and identify:

(_a_) In front of the neck, the _trachea_ or windpipe, with the

_larynx_ or “voice box” at its upper end between the halves of the

lower jaw.

(_b_) The bones of the neck-part of the _spine_.

5. =The trunk.=—Feel through the skin and make out the _spine_, the

_breast-bone_, and the curved _ribs_ which connect these. The spine,

breast-bone, and ribs together form a bony cage which encloses the

fore-part (the _thorax_) of the body. The hinder and larger part of the

body (the _abdomen_) is not protected by ribs, but the bones of the

spine are largest and stoutest in this part of the body.

6. =The limbs.=—How many limbs has the rabbit? Which pair is the

longer? Is the difference in length an assistance in leaping? Make out

the main divisions of each limb, and, by feeling through the skin, the

manner of attachment of its bones to the bones of the body (Fig. 161).

7. =The tail.=—Notice the length, shape, position, and colour of the

tail. The chain of bones inside it is a prolongation of the spine.

=Methods of studying animals.=—In studying animals, methods similar

in principle to those described in previous chapters for plants should

be employed. A real knowledge of the =habits= of animals can only be

obtained by watching them as closely as possible in their natural

surroundings. It is often very difficult to get sufficiently close

to shy animals to see them distinctly without causing alarm, and a

good field-glass is a valuable help in such cases. A great deal of

first-hand knowledge of wild life can, however, be gained without such

aids if the student will learn to move quietly and silently, and to

remain motionless as soon as he is in a good position for observation.

The books of such masters of woodcraft as Richard Jefferies, William

J. Long, Ernest Thompson Seton, and W. H. Hudson give charming

descriptions of the methods of tracking and studying wild animals, and

should be carefully read by every field-naturalist. Observations made

in the field should be at once recorded, with the date, in a note book.

Many animals can be kept for some time, without cruelty, in

confinement; and a more intimate knowledge of certain of their habits

can be thus obtained. The practice of keeping =pets= is, however, to be

encouraged only when every possible care is taken to secure the comfort

of the captives.

To understand the internal structure of an animal, =dissection= is

necessary. This consists in exposing and separating the internal organs

of the dead animal from each other, in order to notice their mutual

relation. A careful outline drawing of every dissection should be

made and preserved. The student should make it a rule never to kill

_any_ animal unless for some useful purpose, and then to do so in the

quickest and most painless manner.

=The habits of the rabbit.=—Wild rabbits live in =burrows= or

underground passages which they excavate, by means of their strong

feet, in the soil of sandbanks, fields, woods, etc. The animals

are sociable, and the burrows belonging to any one community are

collectively known as a =warren=. The passages of the warren

communicate with the outside world by means of openings, some of which

are in common use, while others seem to be used mainly as “bolt-holes”

in cases of sudden alarm. A rabbit which is bolting to its burrow

exposes the white underside of its tail, and thus acts as a danger

signal and guide to its fellows. When a rabbit is startled, or puzzled

by seeing some unusual object, it generally thumps the ground smartly

with its long hind-foot; other rabbits in the neighbourhood are thereby

warned.

[Illustration: FIG. 159.—Rabbits.]

It is common to find, outside a rabbit warren, a number of intersecting

paths, perhaps nine inches wide, and worn smooth by the patter of

little feet. These are the highways, or “runs,” which lead from the

holes of the warren to the various feeding-grounds.

Rabbits breed very rapidly; it has been estimated that in five years a

single pair might have about a million descendants, were it not for the

countless mishaps to which rabbits are exposed. The young are born and

suckled in a special shallow burrow, which the doe excavates and lines

with dry leaves, fur, etc. When she leaves the nest for any purpose she

covers up the entrance with soil.

The proportions of the parts of the body of a very young rabbit are

markedly different from those of the adult. The head is relatively

larger, the tail longer, and the ears shorter; while the hind limbs

and fore limbs are of almost equal length. During the first six months

of its life the animal gradually takes on the proportions of the

adult—with small head, long ears, large hind legs with long feet, and

small, upwardly-turned tail.

A rabbit is able to stand upright on its hind legs, and to maintain

itself in this position for a considerable time. It thus obtains a

wider view and a greater choice of food.

The great difference in the length of the fore and hind legs gives

the animal a characteristic gait. “In a freely moving rabbit,” says

Jefferies, “both fore-feet stop when the hinder come up—one hinder

foot slightly behind the other, and rather wide apart.” Rabbits are

exclusively vegetarian feeders, living on green herbs and on the tender

shoots and bark of shrubs and young trees.

=The external characters of the rabbit.=—The outside of the rabbit’s

body is almost entirely covered with =fur=. This consists of two

kinds of hair—coarse and fine. The coarser hairs are fewer in number

and longer than the fine ones, which they protect from wet. The fine

hairs are extremely closely-set, and stand straight out from the skin.

In a seal-skin coat only the short hairs of the fur are to be found;

the longer hairs have been removed by the dressing process. The great

warmth of furs is due to the air which is entangled between the fine,

close hairs. It is generally the case that fur-bearing animals are

exposed to either mud or wet by their method of life; in spite of this

fact, while the hair of a dog soon becomes wetted by rain, and the

wool of a sheep retains a great deal of dirt, furred animals are noted

for keeping their coats clean and dry.

The longest hairs of the rabbit are the stiff =whiskers= which stand

out from the upper lip, the cheeks, and above the eyes. They are

extremely sensitive to touch, and are of great assistance to the animal

in finding its way through the dark burrows.

The =colour= of the wild rabbit is greyish brown, except on the belly

and under the tail, where it is white. This colour harmonises well

with the surroundings, and renders the animal much less noticeable.

Wild rabbits are exposed to so many enemies, that individuals which

happen to be born with conspicuously coloured fur have generally

but a poor chance of surviving and leaving offspring to inherit

their disadvantages. There is thus in each generation a =natural

selection= of the animals which are best protected, by their colour,

from observation. Among tame rabbits, on the other hand, =protective

colouration= is of very little importance, and one variation of colour

is as likely as another to be transmitted by =heredity= to the next

generation.

=The regions of the body.=—For convenience and precision in describing

animals it is customary to use the words =anterior= and =posterior=

to indicate the fore, or head, end, and the hind, or tail, end

respectively. The belly-surface is said to be =ventral=, and the back

=dorsal=.

The body of a rabbit obviously consists of head, trunk, a short tail,

and four limbs. The general arrangement of the bony framework, or

=skeleton=, (Fig. 161) which supports the softer parts may be felt

through the skin. The skeleton consists of (1) the _skull_; (2) the

spine or _vertebral column_ (generally spoken of as the backbone),

placed dorsally, and reaching from the anterior end of the neck into

the tail; (3) the ventral _sternum_ or breast-bone, which is connected

with the vertebral column by means of curved _ribs_; (4) the bones of

the two pairs of limbs, with the shoulder-and hip-bones to which they

are attached. The bones will be studied in more detail in the next

chapter.

The trunk is divided into two regions—an anterior =thorax=, or chest,

(enclosed in the bony cage formed by the ribs, sternum, and the

adjoining part of the vertebral column), and a posterior =abdomen=. The

two cavities are divided from each other by a fleshy partition called

the _diaphragm_.

=Organs of special sense.=—In addition to the sense of touch which is

possessed by the whole surface of the body, the rabbit has organs which

enable it to distinguish objects by sight, sounds, scents, and taste.

Its sense of =smell= is so keen that, to be successful in snaring

rabbits, “in walking to the spot selected for the snare it is best to

avoid even stepping on the run, and while setting it up to stand back

as far as convenient and lean forward. The grass that grows near must

not be touched by the hand, which seems to impart a very strong scent.

The stick that has been carried in the hand must not be allowed to fall

across the run; and be careful that your handkerchief does not drop

out of your pocket on or near it. If a bunch of grass grows very tall

and requires parting, part it with the end (not the handle) of your

stick.”[8]

The shape of the =ear-flaps=, which can be turned in different

directions (Fig. 159), enables the rabbit to catch very slight sounds.

The =eyes= are placed on the _sides_ of the head, so that the animal

has a wide field of view, and an enemy approaching from behind is

not likely to be unnoticed. The eye of the rabbit is very similar in

structure to our own, but it possesses one useful adjunct which ours

has lost, in the shape of a _third eyelid_—an opaque flap of skin which

lies in the inner angle, and can be drawn over the eyeball at will.

The little fleshy nodule in the corresponding position of the human eye

is a rudiment of a similar structure.

=The rabbit a gnawing animal.=—Rabbits are much addicted to gnawing

young trees for the sake of the bark and the softer juicy tissues

between bark and wood. Even tame rabbits exhibit the same instinct by

gnawing their wooden hutches, although these are of no use as food.

The gnawing is done by the sharp teeth, called =incisors=, which are

conspicuous in the middle of both upper and lower jaw. In the upper jaw

two incisors (which are so deeply grooved that they look like four)

are visible even when the mouth is closed, owing to the split in the

middle of the upper lip. The hardest part of the tooth (a substance

called _enamel_) is at the front. Behind this the tooth is composed of

a softer, bony material called _dentine_; and the back of the tooth

consists of still softer dentine. The result of these differences in

the composition of the various parts of the tooth is that the gnawing

of hard substances wears away the back of the tooth most, the middle

part next, and the front least of all; and thus a sharp chisel-edge

is always maintained. Moreover, _the teeth of the rabbit never stop

growing_, so that they never become appreciably shorter through use.

Immediately behind the two visible incisors of the upper jaw, another

and smaller pair can be felt by the finger; the enamel-faces of these

are directed backwards towards the cavity of the mouth. The softer and

more easily worn faces of the two pairs of upper incisors are thus in

contact, and are continually worn down to form a groove. Into this

groove the two incisors of the lower jaw bite. The incisor teeth stand

well out from the jaws, and the split upper lip can be drawn back, so

that the lips are not injured by gnawing. In the hinder part of the

mouth, where the chewing, or =mastication=, of the food takes place,

are six flatter but cross-ridged =grinding teeth= on each side of

the upper jaw, and five on each side of the lower jaw. The insides of

the cheeks are protected from sharp splinters of wood by a patch of

=hair= on each side, which extends from the region of the incisors to

the grinding teeth behind. The roof of the mouth is protected by hard

cross-ridges, and the tongue by tough skin.

=Rodents.=—Rabbits and hares, rats and mice, and squirrels are said to

be rodents (Lat. _rodo_, I gnaw), as they not only agree in the gnawing

habit, but also in other very important respects.

=Mammals.=—Rodents, and all other animals which suckle their young,

are included by naturalists in the class Mammalia. These animals agree

further in breathing air, in having warm blood, and in being more or

less completely covered with hair.

=Vertebrates.=—Mammals, birds, reptiles, amphibians, and fishes are

grouped together to form the sub-kingdom Vertebrata. They are given

this name because they all possess a spinal, or vertebral, column

(which usually consists largely of a chain of bones), running below the

dorsal surface (p. 217) of the body, from neck to tail.

=The position of the rabbit in the animal kingdom.=—It is clear from

the above that the rabbit is, in the first place, a =vertebrate=

animal; it belongs, secondly, to the _mammalian_ class of vertebrates,

and thirdly, to the _rodent_-order of mammals.

EXERCISES ON CHAPTER XII.

1. In what respects does the hind-foot of a rabbit differ

from the fore-foot? What is the use of the difference?

2. Describe the way in which a rabbit runs. What precautions

does it take when feeding in an open place? (1901)

3. Make observations of the habits and external characters

of hares, and compare them, point for point, with those of

rabbits.

4. Describe the inside of a rabbit’s mouth, and explain the

advantages of any peculiar features to be seen in it.

5. Mention the two chief constituents of a rabbit’s tooth.

Describe by what means the edges of a rabbit’s incisor

teeth are kept sharp.

6. Make a list of all the vertebrate animals with which you

are acquainted. Why are they called vertebrates?

7. By what external characters would you recognise that an

animal was a mammal?

FOOTNOTE:

[8] Jefferies, _The Amateur Poacher_ (Smith, Elder & Co.).

CHAPTER XIII. HOW A RABBIT LIVES.

44. THE SKELETON AND MUSCLES

1. =The examination of the bones.=—In a boiled rabbit clear away the

flesh from the bones. Before separating a bone, notice carefully how

it is attached to neighbouring bones. Notice also, especially in the

limbs, the attachment of the bundles of flesh (_muscles_) to the bones,

the ends of each muscle being fixed to separate bones. Notice that the

places of attachment of the largest muscles are marked by ridges or

roughnesses on the bones.

2. =The skull.=—Observe the two rounded knobs at the back of the skull,

which fit into hollows on the first bone (vertebra) of the vertebral

column. In the skull notice the saw-like boundaries of the various

bones, and make out: the great, rounded _brain-case_; the external

openings of the _ears_; the _eye-sockets_; the snout, with the two

_nasal chambers_; and the upper and lower _jaws_. Before separating the

lower jaw observe carefully how it is hinged on the arches which run

below the eyes, and notice the great muscle on each side which moves

it. Examine the _teeth_ in detail, and remove them one by one from

their sockets. Notice the bony shelf or palate separating the nasal

chambers from the cavity of the mouth. Draw a side view of the skull.

Shave off the top of the brain-case with a sharp knife, and examine the

_brain_.

3. =The vertebral column.=—Make out that each of the bones (vertebrae)

which compose the vertebral column is really a ring, and that the whole

column is therefore a bony tube. In this tube is enclosed the spinal

cord, a backward continuation of the brain. Examine and draw vertebrae

from the various parts of the column, and notice how they vary in shape

and size. Compare vertebrae from (_a_) the neck, (_b_) the region of

the chest (notice the attachment of the ribs), (_c_) the abdominal

region, (_d_) the region of the hips (four united vertebrae; leave

these for the present in position between the hip-bones), (_e_) the

tail.

4. =The ribs and sternum.=—Examine the manner of attachment of the

anterior (p. 217) pairs of ribs to the sternum or breast-bone. Some of

the more posterior ribs are free at their ventral ends.

5. =The bones of the fore-limb.=—Examine the bones in order and make

out: (_a_) the triangular shoulder-blade, (_b_) the single long bone

of the upper arm (its upper, rounded end fitting into a socket in the

shoulder-blade; its lower end forming, with the bones of the fore-arm,

the elbow joint), (_c_) the two bones of the fore-arm (these lie side

by side; notice the peg which makes it impossible for the hinged

elbow-joint to be bent back beyond a straight line), (_d_) the small

bones of the wrist, (_e_) the bones of the hand.

6. =The bones of the hind-limb.=—Notice that the limb as a whole is

divided into parts—upper leg, leg, ankle and foot—which correspond to

the divisions of the fore-limb. Make out: (_a_) that as the bone of

the upper arm fits into a socket in the shoulder-blade, so the bone

of the upper leg has a ball-shaped end which works in a socket of the

hip-bone. Notice that the two hip-bones are joined together ventrally,

and that they are fixed to the welded vertebrae of the hip-region. Does

this give increased strength to the hind-limb? Identify: (_b_) the two

bones of the leg (between knee and ankle) and notice that they differ

from the corresponding bones of the arm in being fused together in the

lower part; (_c_) the bones of the ankle, and (_d_) the bones of the

foot.

7. =The structure of a long bone.=—Take the long bones of the upper

arms and upper legs, and examine them further. Break one across the

middle. Is it solid or hollow? What is the advantage of its being

hollow? Is the tube empty or does it contain marrow? Are the ends of

the bone hollow or solid? Place one of the bones on a bright hot fire.

Is there any sign of burning? Does all the bone burn away? Carefully

remove what is left, and compare the brittleness of the “burnt” bone

with that of an unburnt bone. Place another bone for several days in

a cupful of water to which has been added about two teaspoonfuls of

strong hydrochloric acid. Then take it out, wash it; and try to bend

it. Continue the treatment until the bone is soft enough to tie in a

knot. Can you tie an ordinary bone in a knot? Why not? Put a “burnt”

bone in similar dilute acid. Does it dissolve? What do you think gives

a bone its hardness?

8. =Bones moved by muscle.=—Stretch out one of your arms and grasp

the middle of the upper arm firmly with the other hand. Now bend the

elbow, and notice that the great muscle (the _biceps_) of the front of

the upper arm thickens and becomes shorter. Straighten the arm again,

and notice that the muscle becomes thinner and longer again. Examine

Fig. 160, which shows how the upper end of the biceps is attached at

_a_ to the shoulder-blade and its lower end to one of the bones of the

fore-arm at _P_. If the biceps muscle shortens, the fore-arm must be

pulled up, because the shoulder remains stationary.

Carefully notice the various movements of which your arm is

capable—_e.g._ extension of the arm; bending (flexure) on the

elbow-joint; rotation of the fore-arm, so that either the palm or the

back of the hand can be turned upwards; and grasping. Observe your

power of touching the tip of the little finger with that of the thumb.

If a human skeleton is accessible watch how one (which?) of the two

long bones of the fore-arm rotates when the hand is turned over. How

many of these movements can the rabbit make?

=The uses of the skeleton.=—The bodies of vertebrate animals (p. 220)

are supported, and their more delicate parts protected from injury,

by an internal framework called the skeleton. In some of the simpler

fishes this is composed of gristle or “cartilage”; but in more highly

developed animals it consists almost entirely, in the adult state,

of bone. Further, almost all the bones are connected with strands or

bundles of red flesh called =muscle=, which the animal is able to

shorten or “contract” at will. When a muscle shortens, the bones to

which its ends are fixed are of necessity pulled nearer to each other.

If the bone at one end of the muscle remains stationary, that at the

other end is moved into a new position. This is, generally speaking,

the manner in which the numberless movements of the limbs, head, etc.,

are made.

[Illustration: FIG. 160.—The action of the Biceps muscle. _a_, the

attachment of the muscle to the shoulder-blade; _P_, attachment of the

muscle to the fore-arm; _F_, elbow; _W_, hand.]

=The movements of the limbs.=—An excellent illustration of this

relation between the bones and muscles is seen in the bending of the

arm at the elbow. When the arm is bent, a great mass of flesh, the

biceps muscle, in front of the upper arm may be observed to become much

thicker. The muscle (Fig. 160) thickens because it becomes shorter. Its

upper end is attached to the corner of the shoulder-blade (_a_), which

remains stationary; while its lower end is connected at _P_ with one

of the bones of the fore-arm. The shortening of the muscle therefore

draws up the fore-arm. The elbow-joint, about which the motion takes

place, is a very perfect hinge. Several other forms of joint are also

found in various parts of the body. It is seen, when the skeleton is

examined, that in every case the characters of the joints and the

attachment of the muscles are most admirably adapted to the movements

with which they are associated.

=The study of the skeleton.=—The study of the rabbit’s skeleton is not

only highly interesting in itself, but necessary for the intelligent

appreciation of the animal’s life. And when it is compared with the

skeletons of other familiar animals, a common plan of structure is

found which illustrates in the most convincing manner the kinship which

often exists between very dissimilar creatures. Such a comparison

shows that, almost bone for bone, the skeleton of a rabbit corresponds

with that of a man or a horse, and even with that of a bird or a frog.

Mounted skeletons are shown in most natural-history museums, and the

student should, whenever possible, examine and compare them.[9] He can

himself, however, easily separate the bones from a boiled rabbit, and

make out their main features and relationships.

=The rabbit’s skull and backbone=—The bones of the head are

collectively known as the =skull=. This consists of (1) a large brain

case; (2) the cavities for the organs of special sense, viz., (_a_)

a pair of nasal chambers (in which the organ of smell is located) in

front: their hinder ends open into the top of the throat; (_b_) the

eye-sockets at the sides, and (_c_) the flask-shaped chambers for the

internal ears at the sides of the hinder end of the brain-case; (3)

the jaws: the upper jaw is rigidly attached to the brain-case, but the

lower jaw is hinged at each side on the hinder end of the bony arch

which runs below the eye. Both upper and lower jaws bear teeth, which

are fixed in sockets. On each side the upper jaw contains two incisor

teeth (p. 219) and—much further back—six grinding teeth. In the lower

jaw are one incisor and five grinding teeth on each side.

[Illustration: FIG. 161.—The Rabbit. The skeleton in position, seen

from the left side.]

The =vertebral column= or backbone is a chain of bony rings or

_vertebrae_ which runs dorsally (p. 217) from the hinder end of the

skull to the tail, and forms a long tube containing the spinal cord—a

backward continuation of the brain. On the anterior face of the first

vertebra are two hollows into which a pair of knobs on the skull fit.

Although, with the exception of the first and second, all the vertebrae

are formed on essentially similar lines, there is considerable

variation in shape and size in the different regions of the spine, as

may be seen from Fig. 161. There are seven neck vertebrae, and this

number is remarkably constant in mammals (p. 220). Following these

are the chest vertebrae, which bear pairs of =ribs=. The majority of

the ribs curve round and join on to a ventral bar of bone called the

=sternum= or breast bone; so that the cavity of the chest, containing

those very important organs the heart and lungs, is enclosed in a

protective bony cage. The vertebrae of the abdominal region of the body

are very large and stout. Between them and the tail-bones are four

fused vertebrae, forming a mass which on each side gives attachment to

the large hip-bone.

=The bones of the rabbit’s limbs.=—The fore and hind-limbs of the

rabbit are obviously comparable: the upper arm corresponding to the

upper leg, the elbow to the knee, the fore-arm to the “leg,” the wrist

to the ankle, and the fore-foot to the hind-foot. This similarity

becomes even more apparent when the limb-skeletons are examined.

Commencing in each limb at the end nearest the body we find a single

long bone. In the fore-limb the rounded, upper end of this bone

works in a socket at the anterior angle of the =shoulder-blade=, a

triangular plate on each side which overlies the chest dorsally; in

the hind-limb the rounded end of the corresponding bone works in a

cup in the =hip-bone=. Again, between the elbow and the wrist are two

bones lying side by side; and between the knee and the ankle are two

corresponding bones, although here they are only separate in their

upper parts. Similarly, the wrist bones correspond to the ankle bones,

and the bones of what may be called the fingers to those of the toes.

Certain of the ankle bones are, however, much elongated: obviously a

great advantage to an animal which progresses by a series of hops—owing

to the increased leverage which is thereby given to the hind-foot. The

rabbit’s fore-foot bears five toes, the hind-foot four.

=The structure of a long bone.=—The long bones of the limbs are hollow

except at the ends. Strength and lightness are thus secured by a

device (the hollow cylinder), which has already (p. 72) been seen to

be adopted by the supporting structures of plants, and is also copied

by human engineers. The cavity of the tube is filled by marrow, which

supplies the bone with food. The hard, bony tube itself is partly

composed of mineral matter and partly of animal matter. The mineral

matter is left as a white, brittle framework when the animal matter

is burnt away; while on the other hand the mineral part—which gives

the bone its rigidity—may be dissolved out by immersing the bone in

dilute hydrochloric acid, leaving the organic tissue as a soft flexible

substance having the shape of the original bone.

45. HOW THE RABBIT DIGESTS ITS FOOD.

[Illustration: FIG. 162.—Experiment to show that starch solution will

not pass through a thin membrane. _b_, beaker; _w_, water; _p.p._,

parchment paper; _t.t._, stem of thistle funnel; _s_, starch solution

in head of thistle funnel.]

1. =A solution of starch will not pass through a thin membrane.=—Rub up

with water as much starch as will lie on a shilling, so as to form a

thin “cream,” and then pour on it about a cupful of boiling water. The

starch swells up and largely dissolves in the water. Add a few drops of

the starch solution to about half a pint of water, stir, and test it

by adding a little iodine solution (p. 2, footnote). A beautiful blue

colour is obtained, showing that the test is a very delicate one. Now

take a thistle funnel and with a file cut through the stem about six

inches below the head. Wet a piece of parchment paper or thin bladder

(having previously held it up to the light to be sure there are no

holes in it), and tie it tightly across the mouth of the funnel. Fill

the head and about an inch of the stem with the starch solution. This

can easily be done by means of a “canula,” such as is used for filling

fountain pens. Now put the funnel into a beaker of water, in the manner

shown in Fig. 162, and put the arrangement aside for a few hours.

After that time add iodine solution to the water in the beaker. No

blue colour is formed, showing that no starch has passed through the

membrane.

2. =A solution of sugar will pass through a thin membrane.=—A delicate

test for certain varieties of sugar (not, however, table sugar) is a

liquid known as Fehling’s solution.[10] Place a particle of honey in a

test tube with a teaspoonful of Fehling’s solution, and put the test

tube into a vessel of boiling water. Notice that in a short time the

blue colour of the solution disappears and the liquid becomes red and

turbid.

Now repeat Experiment =45, 1=, but instead of starch solution use

honey dissolved in water. To show that some of the honey-sugar has

passed through the membrane, take about a teaspoonful of the water in

the beaker, and put it in a test tube with twice as much Fehling’s

solution. Heat as before, and notice the red turbidity. If table sugar

is used it may be recognised by the sweet taste of the water after the

experiment.

3. =The action of saliva on starch.=—(_a_) Chew a piece of india-rubber

to induce a free flow of saliva, and collect the liquid. In one test

tube put half a teaspoonful of starch solution; in a second tube put a

mixture of equal quantities of starch solution and saliva; in a third

put saliva alone. Keep the tubes at blood heat for twenty minutes.

Then add a little water to each tube and divide its contents into two

parts. Test one part of each for starch with iodine solution, and the

other part for sugar with Fehling’s solution. The first tube contains

only starch. The second now contains no starch, but shows the presence

of sugar. The third contains neither starch nor sugar. _Evidently the

saliva has changed the starch of the second tube into sugar._

(_b_) Repeat the experiment, but keep the mixture of starch and saliva

in a _cold_ place. No sugar is produced.

(_c_) Repeat the experiment as in (_a_), but use saliva which has been

heated to boiling in a test tube. No sugar is formed.

=The necessity for food.=—It is common knowledge that a rabbit, like

every other animal, must have a regular supply of food if it is to

continue healthy, and that it would soon die outright if food were

withheld. The reason for this is that the living substance of the

animal’s body is incessantly wasting away. The rabbit cannot move a

muscle except at the expense of the living substance of the muscle,

and the more active is its life, the more rapidly does its body waste.

It is to counteract this continual waste by continual formation of new

living substance that food is taken.

But the succulent plants which the rabbit eats are not suddenly

transformed into animal muscle and bone, and so forth, when they are

swallowed. They have first of all to undergo a process which is called

=digestion=. This takes place in a tube—the digestive canal—which runs

from end to end of the body. The digestive canal of the rabbit is

coiled in a somewhat intricate manner. That of the frog is, however,

much simpler and more typical of vertebrates (p. 220) generally, and

will serve equally well in so elementary a consideration of digestion

as the present.[11]

=The frog’s digestive canal.=—The hinder end of the frog’s mouth opens

(Fig. 163) into the =gullet= (_gul._), a short wide tube which leads to

a capacious bag called the =stomach= (_st._). The termination of this

is continuous with a coiled narrow tube called the =small intestine=

(_s. in._), which passes suddenly into a much wider =large intestine=

or rectum. The rectum opens to the exterior, at the hinder end of the

body, by an aperture (_an._) known as the anus. In addition to the

digestive tube proper, two large digestive glands, the liver and the

pancreas, should be carefully noticed. The =liver= (_lr._) is a large,

dark red organ, consisting of two lobes which lie at the sides of the

stomach. It makes a digestive fluid called _bile_. The =pancreas=

(_pn._) is an elongated body which lies in the loop between the stomach

and the first portion—called the _duodenum_ (_du._)—of the small

intestine. It makes a digestive fluid called the _pancreatic juice_.

In the frog both the bile and the pancreatic juice are discharged into

the duodenum by one tube or duct (_b.d._). Small digestive glands also

occur in the inner wall of the stomach; these discharge a fluid called

_gastric juice_ into the cavity of the stomach.

[Illustration: FIG. 163.—The Frog, dissected from the left side. _gul_,

gullet; _st_, stomach; _du_, duodenum; _s. int_, small intestine;

_an._ anus; _lr_, liver; _pn_, pancreas; _b.d_, bile duct; _bl_,

urinary bladder; _c.art_, _l.au_, _s.v_, _v_, parts of the heart; _cn.

3_, “body” of 3rd vertebra; _eus t._ Eustachian tube; _gl_, glottis,

leading to _l.lng_, left lung, and _r.lng_, right lung; _n.a. 1_, arch

of 1st vertebra; _p.na_, internal opening of nostril; _sp.cd_, spinal

cord; _spl._ spleen; _tng_, tongue; _kd_, kidney; _ur_, ureter; _vo.t_,

vomerine teeth.]

=The rabbit’s digestive canal=—In its main features the digestive canal

of the rabbit resembles that of the frog; here also the mouth opens

into a long tube consisting of gullet, a bag-like stomach, a small

intestine, and a large intestine. There are also a liver and a pancreas

which discharge their fluids—by separate ducts, however,—into the first

part of the small intestine; and the stomach is supplied with gastric

juice by small glands in its inner wall. There are, however, certain

differences besides those of size in the digestive tubes of the two

animals. In the first place, a fluid called _saliva_ is poured into the

rabbit’s mouth by the ducts of salivary glands which occur near the

mouth. Secondly, the coils of the small intestine are very much more

complicated than in the frog. And lastly, at the junction of small and

large intestines there is given off, in the rabbit and in herbivorous

mammals generally (when these have simple stomachs,—p. 261), a great,

spirally-constricted tube which ends blindly in a finger-like process.

=How the rabbit digests its food.=—A rabbit needs food to repair the

constant waste of substance which the activities of its life entail;

and the same is true of every other living thing, be it plant or

animal. Now, every part of a rabbit’s body is irrigated and drained by

the finest branches of a system of pipes through which blood is always

flowing; and it is in this blood-stream that the food is conveyed to

the muscles and other organs which are to be repaired. The food finds

its way into the blood when that fluid is flowing through the small

vessels which lie in the thickness of the wall of the digestive tube.

Before food can gain access to the blood it must be in a condition

in which it is capable of diffusing through the thin membrane which

separates them. =Digestion is the process which renders food soluble

and diffusible=, and hence capable of passing into the blood. The

food of animals is of several different kinds. A few of these are

soluble and diffusible at the time they are eaten, but most of them are

neither, and therefore require treating according to their nature. This

is why so many different fluids are poured into the rabbit’s digestive

canal. Saliva, gastric juice, bile, and pancreatic juice are each

capable of acting upon certain constituents of the food and rendering

them soluble and diffusible.

It would be beyond the scope of this book to consider the work of

these fluids in detail, but the =action of saliva= is not only fairly

typical, but it can easily be imitated outside the body. =Starch= is a

very common constituent of vegetable foods, and its presence or absence

is readily determined by the blue colour which it gives with a solution

of iodine. Starch is quite insoluble in cold water, but when treated

with hot water it swells up and, to a great extent, dissolves. But a

mere solution of starch cannot get into the blood, for it is incapable

(Expt. =45, 1=) of passing through a thin membrane. On the other

hand, if starch is mixed with saliva, and the mixture is kept at the

temperature of the body, it is found in a short time that the starch

has been changed into sugar, which is not only soluble, but readily

diffuses through a thin membrane. In other words, starch _as such_

is useless to the rabbit as food; only after it has been digested by

conversion into sugar can it be used by the body.

Something very similar often takes place in plants. It was seen (p. 33)

that the cotyledons of a pea become sweet during germination. Starch

is a convenient form of food for storing in the cotyledons of a pea,

the endosperm of the maize seed, the short stem of the crocus-corm,

and so on; but before the plant can use it as food the starch must be

made soluble and diffusible by being changed into sugar. In plants the

change is brought about, not by saliva, but by a substance known as

_diastase_.

The pancreatic juice continues the change of starch into sugar which

is commenced by the saliva, but it also digests other food-stuffs as

well. Similarly, gastric juice and bile are each concerned with the

digestion of certain foods. The result of the action—separate and

combined—of the digestive fluids is that, when a rabbit eats no more

food than it requires, all the useful parts of the food are absorbed

into the blood, and then distributed to the tissues by the blood as it

flows through them.

46. THE CIRCULATION OF THE BLOOD.

1. =Evidence of the circulation.=—(_a_) _The arterial pulse._—Feel your

pulse at the wrist and count the number of beats per minute.

(_b_) _The beats of the heart._—Similarly count how many times your

heart beats per minute. Put your ear over the heart of a friend, and

listen to the sounds of the heart. How many different sounds can you

distinguish?

(_c_) _The valves of the veins._—Press your thumb on your arm inside

the elbow, and then move it down the arm towards the wrist. Notice the

small knots which rise under the skin between the point of pressure and

the wrist.

2. =The structure of a sheep’s heart.=[12]—Procure from the butcher

a sheep’s heart with, if possible, the lungs still attached. If the

thin transparent bag which naturally surrounds the heart has been

left on, carefully cut it away. Make out the main external features

of the heart before cutting into it. The shape is conical, the apex

of the cone being posterior, the base (where the blood-vessels are

attached) anterior. The ventral face is rounded; the dorsal face is

flatter. Compare Fig. 164. The line of fat (_3_) marks the line of

division between two chambers, the right (_R.V._) and left (_L.V._)

_ventricles_. Feel that the right ventricle yields to pressure

more readily than the left. Two more chambers, the right and left

_auricles_, are situated at the basal (thick) end. _R.A._ and _L.A._

are flaps of the right and left auricles respectively. Identify the

great vessels _SVC_ and _IVC_ which discharge into the right auricle.

Cut them open to see the entrance. Then lay open the right auricle.

Pass your finger down and notice that the right auricle communicates

freely with the right ventricle. Observe that you can from the right

ventricle pass your finger into the tube _P.A._; make out that this

goes to the lungs. Lay open the left auricle, and see that it receives

vessels _from_ the lungs. Pass your finger from the left auricle into

the left ventricle, and notice that this latter chamber leads into the

_Aorta_, _Ao._ (_A´o´._ a branch of _Ao._). Notice that the walls of

the blood-vessels in connection with the two auricles are collapsed,

while those (_P.A._ and _Ao._) leading from the two ventricles are more

elastic and remain open. Which of the two auricles has the thicker

wall? Which of the two ventricles has the thicker wall? Can you pass

your finger from one auricle to the other? From one ventricle to the

other? Cut away the auricles and pour water into the ventricles. Then

squeeze the heart gently, and notice the flaps which rise to close the

openings into the ventricles. Could blood pass from the ventricles to

the auricles? Why not? Lay open the bases of the vessels _P.A._ and

_Ao._ leading from the right and left ventricles respectively, and

notice the pockets of thin membrane which are attached there. Open them

out gently with the point of a pencil. Put the heart under the tap and

let water trickle down the vessels towards the ventricles; notice how

the pockets stand out as they fill with water. What would be the effect

of blood trying to pass from _P.A._ or _Ao._ back into their respective

ventricles?

=The circulation of the blood.=—The blood of such an animal as the

rabbit is contained in a system of closed tubes called blood-vessels,

through which the fluid is continually flowing. The regular flow of

the blood in one direction is maintained by the action of the =heart=,

a four-chambered organ which is situated in the chest, between the

lungs. The heart is muscular, and, like other muscles (p. 225), has

the power of “contracting” in definite directions. The contraction of

the walls of the chambers of the heart lessens their capacity, and

therefore drives the blood out of them, the direction of flow being

determined by valves. The vessels which carry blood _to_ the heart are

called =veins=; those which transmit the blood which is pumped _out

of_ the heart are called =arteries=. The arteries branch into smaller

and smaller tubes which supply the various organs of the body, and the

small arterial branches divide again and again in the organs until

their finest ramifications form a close-meshed network of vessels with

excessively thin walls, through which diffusion can readily take place

between the tissues and the blood. These finest blood-vessels are

called =capillaries=. They can be studied in the transparent web of the

frog’s foot with the aid of a low power of the microscope. The blood

can then be seen flowing, at a speed which varies with the size of the

vessel, its course being rendered obvious by the tiny oval particles

(red corpuscles) which are suspended in it. The smallest capillaries

are so thin-walled that they appear to be merely channels in the

substance of the web, and the corpuscles creep along in single file.

But these channels unite to form larger vessels with obvious walls, and

these unite again and again until a main vein is formed in which the

blood, with its suspended corpuscles, rushes along in a swift torrent

towards the heart.

=The heart.=—The beginner will find the sheep’s heart more convenient

for examination than the rabbit’s, on account of its larger size;

but apart from some difference in the arrangement of the great

blood-vessels opening into them, the two hearts are broadly similar.

The heart (Fig. 164) consists of four chambers. Two of these, the

=auricles=, are receiving-chambers, and are placed at the thick,

anterior end of the heart. Into the right auricle open the great veins

(_SVC_, _IVC_,) which bring blood from all parts of the body except

the lungs; the left auricle receives only blood from the lungs. Each

auricle opens into a more posterior chamber called a =ventricle=, the

right auricle opening into the right ventricle and the left auricle

into the left ventricle. The ventricles pump blood into the arteries.

The blood from the right ventricle is sent into the artery (_P.A._)

which supplies the capillaries of the lungs; while the blood of the

left ventricle is forced into the aorta (_Ao._), a great artery which

branches and supplies with blood all parts of the body except the

lungs. The two auricles contract simultaneously, forcing their contents

into the flaccid ventricles. Then both the filled ventricles contract

at once, and pump blood into the great arteries, flaps of membrane

between the auricles and ventricles preventing a backward flow into the

auricles. Similarly the bases of the great arteries are provided with

membranous pockets which readily admit the blood from the ventricles

when these contract, but entirely prevent a return of blood to the

ventricles. The appearance of these four sets of valves, as seen

from above, is shown in Fig. 165. After the contraction of the two

ventricles there is a short rest, then the auricles contract again and

the whole process is repeated.

[Illustration: FIG. 164.—Heart of Sheep, in position between the lungs.

_R.A._, appendage of right auricle; _L.A._, appendage of left auricle;

_R.V._, right ventricle; _L.V._, left ventricle; _S.V.C._, _I.V.C._,

great veins from the system generally; _P.A._, artery to lungs; _Ao._,

aorta; _A´o´._, branch of aorta; _L._, lung; _Tr._, windpipe, leading

to lungs; 2, 3, 4, fat.]

[Illustration: FIG. 165.—The orifices of the heart seen from above,

the auricles and great vessels being cut away. _PA_, valves at base

of artery to lungs; _Ao_, valves at base of aorta; _R.A.V._, orifice

between right auricle and ventricle, with its valves _l.v. 1_, _l.v.

2_, and _l.v. 3_; _L.A.V._, orifice between left auricle and ventricle,

with its valves _m.v. 1_ and _m.v. 2_.]

[Illustration: FIG. 166.—Diagrammatic sections of veins with valves. In

the upper figure the blood is supposed to be flowing in the direction

of the arrow, towards the heart; in the lower, back towards the

capillaries.]

[Illustration: FIG. 167.—A vein laid open to show a pair of

pouch-shaped valves.]

The =sounds= which are heard when the ear is placed over another

person’s heart are often compared to the syllables _lub-dup_. The “lub”

is partly caused by the contraction of the ventricles; the “dup,” which

immediately follows, is caused by the sudden closure of the valves at

the bases of the great arteries. The throb of the heart, which can be

felt from the outside, is really the thrust of the apex of the heart

against the chest-wall at each beat. The sudden forcing of blood into

the already-full but elastic arteries causes a wave to travel along

these vessels, which can readily be felt, or even seen, at places where

a fairly large artery lies just beneath the skin. This arterial wave is

called the =pulse=. Many of the veins are provided with pouch-shaped

valves which permit the blood to flow freely towards the heart, but

which bar the passage of blood in the opposite direction. Their action

will readily be understood from Figs. 166 and 167.

=The importance of the capillaries.=—The capillaries are the least

conspicuous part of the circulatory system, but they are by far the

most important. The heart, arteries, and veins exist merely to renew

constantly the blood which flows through these minute channels. The

excessive thinness of the walls of the capillaries makes it possible

for a ready exchange to take place between the living tissue and the

blood, and the vessels themselves form a network of such extremely

close texture that it is practically impossible to prick any living

part of the body with a fine needle without puncturing some of them and

“drawing blood.” The work of the blood in supplying the various organs

of the body with food has already been referred to. We have next to see

how this all-important fluid is of service in supplying the organs with

oxygen.

47. RESPIRATION.

1. =Carbon dioxide is formed when flesh burns.=—Dry a piece of meat and

attach it to the end of a wire. Then light it, and when it is burning

vigorously lower it into a clean glass jar. When the flame goes out

remove the charred flesh, and at once pour a little clear lime-water

into the jar and shake up. The lime-water turns milky, showing the

presence of carbon dioxide gas in the jar. Examine what is left of the

meat. It is charred, showing that meat contains carbon. How was the

carbon dioxide formed during the burning?

2. =Carbon dioxide is formed by the living body.=—Breathe through a

glass tube into clear lime-water, so that the air you expel from your

lungs bubbles through the liquid. Does the lime-water remain clear,

or turn milky? Does the air you breathe out contain a considerable

quantity of carbon dioxide gas?

=Burning and life.=—When a piece of the flesh of any animal has been

dried it may easily be set on fire. The burning is caused by the union

of the constituents of the flesh with some of the oxygen of the air

to form various gases. One of these gases is carbon dioxide, formed

by the combination of the carbon of the flesh with oxygen. Carbon is

present in all the parts of animals and plants, as is evident from

the separation of charcoal (an impure form of carbon) in the first

stages of burning; the carbon dioxide gas which is formed may easily be

recognised by the milkiness which it produces in clear lime-water. The

liberation of heat, and the formation of carbon dioxide, which always

accompany the burning of animal and plant tissues, are worthy of very

careful attention.

[Illustration: FIG. 168.—Experiment to prove that expired air contains

carbon dioxide.]

It is well known that the body of a living animal such as a rabbit

or a man is always _warm_; and the experiment (Fig. 168) of passing

through clear lime-water the air breathed out from the lungs shows, by

the milkiness produced, that the animal is also constantly producing

carbon dioxide during its life. Is life, then, always accompanied

by a peculiar form of burning, in which the living substance of the

body is the combustible material? It seems so, and the experiments of

physiologists tend to confirm this view.

=The necessity for breathing.=—The energy which enables a muscle to

contract is derived from the oxidation—the slow burning—of part of its

substance, just as the energy which enables a steam-engine to move

is derived from the burning of fuel in the boiler fires. The fires

soon go out, and the engine stops, unless fresh fuel is added from

time to time and a plentiful supply of air is available. Similarly,

a muscle loses its power of contracting, a gland that of secreting,

the brain that of thinking, unless the waste matters resulting from

previous activities are cleared away and replaced by fresh food and

fresh oxygen. Wherever vital action is taking place, whether in a

contracting muscle, a secreting gland, or a thinking brain, there is

continual consumption of oxygen and continual production of waste

material, chiefly carbon dioxide. In the higher animals the renewal of

oxygen and the removal of waste material are performed by the blood.

Blood-vessels are to the body what rivers and canals are to a country:

they act as highways for the transport of material. We may perhaps

carry the analogy a little farther and find in the red corpuscles of

the blood the rough equivalents of boats or canal-barges, for they

carry with them tiny loads of oxygen. As the blood creeps along the

narrow channels in an active tissue the red corpuscles relinquish their

oxygen, and the fluid portion of the blood takes up carbon dioxide.

The blood continues its course, and sooner or later arrives at a place

where it can obtain a fresh supply of oxygen and get rid of its surplus

carbon dioxide. In the rabbit this exchange takes place as the blood

is passing through the capillaries of the =lungs=. There the blood

is separated from the air by a membrane so delicate that gases can

readily pass through it; and, hence, on leaving the lungs the blood has

got rid of the waste carbon dioxide, and its red corpuscles are laden

with fresh oxygen. _This exchange of useless carbon dioxide for oxygen

constitutes respiration or breathing._

=The mechanism of respiration.=—In active animals the air inside the

lungs soon becomes vitiated, unless there is some means of changing

it. Under ordinary conditions a man changes the air in his lungs from

thirteen to fifteen times a minute. He does this quite automatically,

and without thinking about it. Every four seconds or so a set of

muscles contracts and pulls his ribs upwards and outwards; another

muscular contraction pulls down the floor of his chest at the same

time. As a consequence the cavity is much enlarged. The lungs follow

the movements of the walls of the chest, and some thirty cubic inches

of air are sucked in. Immediately the ribs fall back to their former

position, the chest-floor rises, and air is driven out. Then after a

short pause the process is repeated. It should be noticed that only

about thirty cubic inches of air are changed at each respiration,

although the capacity of the human lungs averages about 230 cubic

inches. All mammals breathe in much the same way.

=Plants and animals.=—There are considerably more points of similarity

than of difference between plants and animals. In every case the vital

activities are accompanied by an oxidation of living substance, and

from this fact arises the necessity for food and oxygen. The breathing

of plants is essentially like that of animals, and consists in taking

in oxygen and giving out carbon dioxide; though the _mechanism_ of

respiration is—except in the lowest plants and animals—entirely

different in the two cases. It is in the sources from which they obtain

their =food= that plants and animals are most unlike. An animal must be

supplied with food which has already been prepared by some other living

thing; and it is obvious that the food even of carnivorous animals can

ultimately be traced back to plants, for the flesh-eater preys upon

the vegetarian. Animals are therefore entirely dependent upon plants

for food. In this sense the saying “all flesh is grass” is full of

significance.

Green plants (Chapter II.) are quite independent of all other forms

of life, and can build up their substance from water, mineral matter,

and the carbon dioxide of the air. The taking in of carbon dioxide

and giving out of oxygen by green plants has nothing whatever to do

with respiration; it is part of their process of feeding. Green

plants breathe in the usual manner—by taking in oxygen and giving

out carbon dioxide. It should, however, be noticed that the peculiar

method by which a green plant obtains its carbonaceous food is of the

highest importance to animal life; for by this process the amount of

injurious carbon dioxide in the air is considerably lessened, while the

proportion of life-supporting oxygen in it is greatly increased.

Fungi (Chapter XI.) seem to be intermediate, as regards their method

of feeding, between green plants and animals. They require their

carbonaceous food in an organic form, that is, already prepared by

other living things; but they can obtain the other elements of their

food from mineral salts and water.

The thoughtful student will be increasingly impressed by the extent to

which the plant and animal kingdoms are dependent upon each other, and

by the manner in which each utilises the waste products of the other

for carrying on its own life processes.

EXERCISES ON CHAPTER XIII.

1. Of what parts does the skull of a rabbit consist? What is

the use of each part?

2. Describe one of the long bones of a rabbit’s leg. To what

features does it owe its strength?

3. The bones of the skeleton are useful (1) as affording

points of attachment for the muscles; (2) as affording

protection for delicate tissues and organs. Give examples

of each of these uses. Do not give the technical names for

the various muscles. (King’s Schol., 1902)

4. Draw and describe one of the middle joints of the

backbone of a quadruped, and explain the uses of the

various parts. (1898)

5. What is meant by “digestion”? Why must food be digested?

Where does digestion take place?

6. Give full practical instructions for demonstrating the

chief properties of saliva, and its action upon various

kinds of food. (1897)

7. Prove that the action of human saliva upon starch is not

due to living particles contained in it. (1898)

8. What are the chief uses of the blood? Why is it necessary

that it should be kept in motion? (1901)

9. Where would you look for the Aorta in a sheep’s heart?

What valves are found in it? How does it differ in

appearance and feel from a large vein? (1901)

10. What kinds of valves are found in a sheep’s heart, and

where are they placed? Describe a valve of each kind. (1898)

11. How does air breathed out from the lungs differ from

common air? How can the differences be demonstrated? (1898)

12. Describe the process by which a mammal renews the air in

its lungs.

13. What is meant by “respiration”? Why is respiration

necessary?

14. Point out the most remarkable differences between the

nutrition of a green plant and that of an animal. (1897)

15. Name organisms which can derive nourishment from carbon

dioxide, from sugar, and from the dead bodies of animals.

(1898)

16. What are the simplest functions which distinguish living

animal matter from inanimate matter? (King’s Schol. 1903)

17. Explain as fully as you can how food taken into the

stomach acts upon organs, such as the brain, which are not

closely connected with the stomach. (1904)

18. The uses of bone are, generally speaking, to protect

delicate structures, to support weight and to gain

leverage. Illustrate this statement by a simple

description of one example of each type. (Certificate, 1904)

19. The flow of liquids through the body is regulated in

certain localities by valves. Explain the action of a

valve, and indicate where they are to be found in the

body. (Certificate, 1904)

20. In which kind of blood-vessel can the pulse be felt? In

which kinds can it not be felt? Explain the reason of the

difference. (Certificate, 1905)

21. How is oxygen conveyed from the lungs to the various

parts of the body? Describe what could be observed if a

drop of blood were spread out on a piece of glass and

examined under a microscope. (King’s Schol. 1905)

FOOTNOTES:

[9] See footnote, p. 231.

[10] Prepared by adding to a solution of copper sulphate first tartaric

acid, and then caustic soda until the blue mixture is clear. It may be

obtained from a chemist if the materials are not available.

[11] NOTE TO TEACHERS.—A general dissection of a frog should be made

and exhibited to the class. Detailed instructions for such a dissection

will be found in Marshall’s _The Frog_ (Smith, Elder & Co.) or in

Huxley and Martin’s _Elementary Practical Biology_ (Macmillan). The

frog’s heart continues to beat for some time after the death of the

animal, and may be shown as an illustration of the next section of this

chapter. Teachers who are unskilled in dissection may obtain prepared

dissections, mounted skeletons, etc., from Newmann & Co., 84 Newman

Street, London, W.

[12] More detailed instructions will be found in Foster and Shore’s

_Physiology for Beginners_ (Macmillan).

CHAPTER XIV. SOME OTHER MAMMALS.

48. THE CAT AND DOG.

1. =The external characters of the cat.=—Carefully and gently examine a

cat, and make notes of the following characters:

(_a_) _Hair._—What is the covering of the body like? Is the hair

like that of a rabbit, _i.e._ fur (p. 216)? Are the whiskers very

noticeable? On what parts of the head do they grow? Are the fur and

large whiskers in any way connected with the animal’s habits?

(_b_) _Eyes._—Look at a cat’s eyes in a bright light. Is the pupil (p.

212) round or slit-like? Keep the cat in the dark for a few minutes and

then look again at the pupil of the eye; has it changed in form? Is the

change of any advantage to the cat?

(_c_) _Teeth._—Gently open the cat’s mouth and examine the teeth.

Notice the sharp, pointed teeth behind the incisors (p. 219); they are

called the _canine_ teeth. Has a rabbit any canine teeth? Why does a

cat, and not a rabbit, need such teeth? Feel the remaining teeth with

your finger; are they flat like those of a rabbit, or sharp-edged? How

are the characters of the teeth associated with the kind of food? Watch

a cat eating; does it chew its food or swallow it “in lumps”?

(_d_) _Tongue._—Pass your finger-end over the cat’s tongue; is it rough

or smooth? In which direction of motion of the finger does the tongue

feel roughest? Would the roughness be of any help to the animal in

licking meat from bones?

(_e_) _The limbs._—Measure the legs. Are the fore and hind limbs of

equal length, slightly unequal, or very unequal? How do they compare in

this respect with the limbs of the rabbit? Make out the main bones by

feeling through the skin, and especially notice where the ankle-joint

is. Examine the toes and notice how, when you gently squeeze them just

behind the ends, the sharp _claws_ protrude, and go back into a kind of

sheath when the pressure is removed. Can the animal put out its claws

and draw them back at will?

2. =The habits of the cat.=—(_a_) _Food._—What kind of food does the

cat prefer, animal or vegetable? Does it bolt its food greedily, or

does it eat deliberately and daintily? Have you ever known cats to hunt

other animals? Do they hunt singly, or do several cats join together

to hunt? How do they approach the prey; do they try to run it down by

speed, or do they creep up slyly and then spring? What is the use of

the claws? How does a cat drink?

(_b_) _Locomotion._—Watch a cat moving slowly; does it walk or hop? Try

to find out the order in which it puts its feet down. How does it run?

Is it nimble or clumsy? Does the cat walk with the whole sole of its

foot on the ground, or does it walk “on its toes”?

(_c_) _Likes and dislikes._—Do you consider a cat sociable, _i.e._

fond, in general, of the society of other cats? Do cats, as a rule,

show much appreciation of the difference between right and wrong? Are

they as affectionate as dogs? Have you ever heard of any cat trying to

remain in a house after the family had removed to another house? Are

cats fonder of warm or of cool places in a house? Do they like getting

wet? Do they pay much attention to personal cleanliness? How do they

wash themselves? Do you think the tongue is used as a comb? How? Can

you know whether a cat is pleased or angry (i) by the appearance and

movements of the tail, (ii) by the sounds which it makes?

(_d_) _Intelligence._—Write accounts of cases of great intelligence

which you have known cats to show.

(_e_) _Voice._—How do you describe a cat’s voice? How does the voice

vary according to the animal’s mood?

(_f_) _Play._—How does a cat play?

3. =Kittens.=—(_a_) _Appearance._—Are kittens helpless or active

when they are born? Is there any very marked difference between the

proportions of the body and limbs and those of a full-grown cat? At

what age is a cat full-grown?

(_b_) _Play._—How does a kitten play? How does it pretend to “stalk” a

small object, such as a ball of wool? In the same way that a full-grown

cat stalks a mouse? Why does the kitten adopt this method before it has

any experience of hunting?

(_c_) _Education._—Watch a cat with its kittens, and describe any

actions which seem like education. Have you ever seen a cat teach its

kittens to fight? Have you ever seen it punish a kitten for disobeying

a call?

4. =The external characters of the dog.=—Examine a dog in the same way,

and compare it point by point with the cat as regards the following

characters:

(_a_) _Hair._—Notice that the dog is covered, not with fur, but with

rough hair, and that the whiskers are not very large. How are these

differences associated with differences in habit?

(_b_) _Eyes._—Notice that the pupil is always round, although it is

smaller in a strong light than in a weak one.

(_c_) _Teeth._—Compare the teeth with those of the cat, and notice

that they are of similar form—with strong interlocking canines and a

sharp-edged tooth on each side of the upper jaw which clips against

a similar tooth in the lower jaw—but that the cat’s teeth are more

pointed.

(_d_) _Tongue._—Notice that the dog’s tongue is much smoother than the

cat’s.

(_e_) _Limbs._—Examine and measure the limbs, comparing them with those

of the cat, rabbit, and man. Notice that the claws are blunter than the

cat’s, and that they cannot be withdrawn into sheaths. How many toes

are there on the feet?

5. =The habits of the dog.=—(_a_) _Food._—Does the dog prefer animal

or vegetable food? Watch a dog gnawing a bone, and observe the use of

the clipping teeth. Does a dog eat greedily or deliberately? Does it

chew its food or swallow it in lumps? Do dogs hunt singly or in packs?

Do they stalk the prey stealthily, as cats do, or do they try to run

it down by speed? Whenever possible watch a pack of hounds; upon what

sense—hearing, sight, or smell—do the hounds rely most? How does a dog

drink?

(_b_) _Locomotion._—Does a slowly-moving dog hop or walk? Try to find

out the order in which it puts its feet down. How does it run? Does a

dog walk flat-footed or on its toes?

(_c_) _Likes and dislikes._—Do you consider dogs sociable or otherwise?

Do they seem to know the difference between right and wrong? Are dogs

affectionate? Are they more attached to the people or to the houses to

which they are accustomed? What can you learn of a dog’s feelings, by

the movements of its tail? Write accounts of instances, which you know

to be true, illustrating its likes and dislikes. What expression of the

human face seems to you most like the snarl of an angry dog? What are

the resemblances?

(_d_) _Intelligence._—Write accounts of evidence of intelligence, or

reasoning power, which you have observed in dogs.

(_e_) _Voice._—What is the ordinary voice of the dog? What other sounds

do dogs make, and what do they mean?

(_f_) _Play._—How do dogs play? Do you think dogs have any sense of

humour, or are able to appreciate a joke for the joke’s sake? Have you

ever seen any expression resembling a smile on a dog’s face?

6. =Puppies.=—(_a_) _Appearance._—Are puppies blind and helpless when

they are born, or are they active? How soon can they see? Are the

proportions of the body and limbs markedly different from those of the

full-grown dog? At what age is a dog full-grown?

(_b_) _Play._—Does a puppy play in the same manner as a kitten? What

differences have you noticed? Have these differences any connection

with the methods of catching the prey of the adult animals?

(_c_) _Education._—Have you ever seen a puppy being taught to do

anything by its mother? Write full accounts of such cases.

7. =Different breeds of dogs.=—Make notes of your observations of as

many different breeds of dogs as possible, _e.g._ collies, terriers,

retriever, fox-hound, pointer, spaniel, etc., and describe the

resemblances and differences in size, form, habits, intelligence, etc.

[Illustration: FIG. 169.—The Cat.]

=The external characters of the cat and dog.=—The cat and the dog are

so commonly kept as pets that they are perhaps more easily examined

than any other animals. In addition, they are so closely related and

yet exhibit so many differences that they afford a valuable exercise in

the methods of =comparison and contrast= which are at the foundation

of all successful work in Nature-Study. Several differences are at

once apparent on even a casual inspection. The body of the =cat= (Fig.

169) is covered with soft, smooth _fur_, and its head is provided

with long, sensitive whiskers. In both of these respects it resembles

the rabbit and other mammals which are in the habit of creeping along

narrow and dark passages. It is commonly said that cats can see in the

dark. Although this is not altogether true—for no animal can see in

total darkness—the cat’s eyes have the power of adapting themselves

remarkably to the intensity of the light. In a dim light, the curtain,

or iris, which surrounds the pupil (the dark, central window through

which light enters the eye) is drawn back so as to admit as much light

as possible; whereas in a very bright light the curtain is so nearly

closed that the pupil is merely a narrow, vertical slit. On the other

hand, the =dog= (Fig. 170), which is not fond of dark passages, has

its body clothed with _rough hair_, instead of fur; and its whiskers

are not nearly so long as those of the cat. Again, although the iris

of a dog’s eye alters in size to regulate the amount of light entering

the eye, the pupil is always round, and the change of size is much

less marked than in the cat. Another very noticeable difference is in

the =claws= at the ends of the toes, corresponding to the nails at the

ends of our own fingers and toes. In the cat these are sickle-shaped

and extremely sharp, and are kept drawn completely back into sheaths

when they are not required. The dog’s claws are blunt, and cannot be

retracted. Both the dog and the cat rest the weight of the body upon

the toes—not upon the sole of the foot—when walking or running.

[Illustration: FIG. 170.—Foxhound.]

There is also a very marked difference in the =tongues= of the two

animals. The tongue of the cat is rough, with small points directed

backwards. These points are of great help in licking the flesh from

bones; and they also serve as a comb when the cat—which is fastidious

about the cleanliness of its fur—“washes” itself. The tongue of the dog

is smooth and moist.

=The inherited habits of the cat and dog.=—Very obvious differences

are also to be seen in the habits of the two animals, and these would

be somewhat difficult to explain if we confined our attention to the

domesticated animals only, which live under artificial conditions.

When, however, we consider the wild relatives of the cat and dog, many

of the differences become full of significance. The wild animals of

the cat family, almost without exception, are either solitary or live

in pairs; whereas the wild dogs (wolves, jackals, etc.) live in packs.

The habits which these respective methods of life entailed have become

so firmly implanted in the nature of the race that even now, after

thousands of generations of domestication, they may be traced. Such

inherited habits, which are not dependent upon, or may be at variance

with, present conditions of life, are called =instincts=.

We will first see how the ancestral custom of living in organised packs

has left its impress upon the instincts of the domesticated dog. The

first essential to the success of any community of animals—whether

these are bees or rooks, wolves or men—is that all the creatures

composing it shall conform to certain rules, which have for their

object the good of the community and not merely that of the individual.

Acts which promote the wellbeing of the society as a whole are good,

and are directly or indirectly rewarded. Acts which tend to injure the

society as such are bad, and inevitably bring punishment either to

the individual offender or, what is worse, to his pack. A distinction

between right and wrong is thus established which would be impossible

to any animal living so solitary a life that its acts affected only

itself. In this manner were aroused the social instinct, the love

of praise and the dread of shame, the lifelong attachment to early

friends, and almost all the other qualities which have so endeared the

dog to mankind; because these qualities resulted naturally from the

ancestral pack-life. Left to itself, the dog loses its nerve, for it is

by nature unfitted for a solitary life. What more woe-begone animal is

ever seen than a lost dog?

Contrast the cat in these respects. It is at heart an outlaw, like its

wild ancestors: recognising, in general, no motives but those of its

own ease and gratification. Its social instinct is almost absent; and

though it sometimes displays affection to people who pet it, the cat

is, as a rule, more attached to places than to persons. It retains,

too, the independence and versatility which are developed by a solitary

life. A lost cat can usually take care of itself and find sufficient

food; and cases are not uncommon of cats leaving comfortable homes and

choosing to live wild lives in the woods.

Ancestral methods of =hunting= also account largely for certain

differences in the domestic cat and dog. The solitary ancestral cats,

like the lions and tigers of to-day, sprang suddenly upon the prey at

the end of silent, stealthy stalking. How firmly this method has become

fixed in the character of the race may be seen still in the manner in

which a cat stalks a mouse or a small bird, or even, in play, a dead

leaf. At the final spring the sharp, sickle-shaped claws are used to

hold down the victim. The solitary hunter is able to devour its capture

at leisure, and the domestic cat is still distinguished by its dainty

and deliberate manner of feeding.

The wild dogs hunt in a quite different manner. The whole pack joins

in the chase, the trail being followed by the sense of smell. There is

no attempt at concealment, no stealthy stalking; but an open reliance

upon speed, endurance, and numbers, rather than upon cunning. If one

dog loses the scent another picks it up and gives the signal. Mutual

help is thus the secret of success in hunting. But this is at an end

when the prey is killed. The victim is torn to pieces and devoured

greedily, each animal eating as rapidly as possible, for in most cases

there is not enough to satisfy them all. And the well-fed domestic dog

still betrays the ancestral necessity for hurried eating in the manner

of bolting his food.

=Methods of expressing feeling.=—Animals express their feelings in

various ways—by the voice, by the face, by the tail, and by the general

attitude of the body. Perhaps no animal’s feelings are more readily

recognised by man than the dog’s. “It is a remarkable fact,” says

Darwin,[13] “that the dog, since being domesticated, has learnt to bark

in at least four or five distinct tones. Although barking is a new art,

no doubt the wild parent-species of the dog expressed their feelings

by cries of various kinds. With the domesticated dog we have the bark

of eagerness, as in the chase; that of anger, as well as growling; the

yelp or howl of despair, as when shut up; the baying at night; the

bark of joy, as when starting on a walk with his master; and the very

distinct one of demand or supplication, as when wishing for a door

or window to be opened.” The movements of the tail are also full of

meaning, and capable of expressing several different moods. It seems

likely that in a dog the movements of the tail were originally of use

chiefly to signal to the rest of the pack. The use of the movements of

a cat’s tail is not very clear, although these also differ according to

the animal’s feelings.

=Carnivores.=—Dogs and cats, with several other mammals, which are

mostly flesh-eaters, are called =Carnivores=. They have never fewer

than four distinct toes on each foot, and the claws (nails) are often

capable of being withdrawn into sheaths. The teeth (Fig. 171) are

characterised by the large, interlocking canines, which are conical,

curved, and pointed; and by one of the cheek teeth on each side having

a sharp, cutting edge which bites against the similar tooth of the

other jaw, almost in the manner of the blades of scissors. The seals

and walruses, however, which are carnivores adapted to living in water,

have no such clipping teeth.

[Illustration: FIG. 171.—Skull of Wolf, seen from left side.]

49. THE BAT.

1. =Habits.=—At what time of the year have you seen bats flying about?

Do they fly in broad daylight, or only in the evening? How can you

distinguish a bat’s flight from that of a bird? Have you ever heard a

bat squeak? Upon what does it feed? Are flying insects plentiful in

winter? Have you ever seen a bat drink? How does it drink? What does

the bat do in winter? Try to find a sleeping bat in winter in a barn, a

hollow tree, or a belfry. What is its position?

2. =Appearance.=—Examine a sleeping bat or a stuffed specimen. What

is its body covered with, hair or feathers? Is it a bird or a mammal?

Is the hair soft and furry? How large are the ears? Are the whiskers

large or small? What are the wings like? Can you see any fingers?

How many fingers are there? Do any of the fingers bear claws? Do the

fingers support the wings? Which are longer, the fore limbs or the hind

limbs? Do the toes of the hind limbs bear claws? What is their use? If

possible, put a live bat on the ground; does it walk easily? Apart from

the wings, what animal does the bat seem most to resemble? Do you know

of any other flying mammal?

=The Bat= (Figs. 172 and 184_a_).—On summer evenings in most country

districts of Britain bats may be seen flitting about catching insects.

The flight is peculiar, and somewhat suggestive of that of a butterfly,

so that even in the dusk the animal may be distinguished easily from

a small bird. “Bats drink on the wing like swallows, by sipping the

surface as they play over pools and streams. They love to frequent

waters, not only for the sake of drinking, but on account of insects,

which are found over them in the greatest plenty.”[14]

[Illustration: FIG. 172.—The Bat. (× ⅓.)]

The voice of the bat is a shrill squeak, of so high a pitch that many

people cannot hear it at all. The animal is probably quite blind, but

it has keen powers of scent and hearing, and in avoiding obstacles

seems to be greatly aided by patches of specially sensitive skin on the

face, and by delicate whiskers. During the day it lurks in dark corners

of barns, church-towers, hollow trees, etc., hanging head downward by

the hooked claws of its hind feet.

On close examination the body of the bat is seen to be covered with

soft =fur=, a character which at once proclaims the animal to be not a

bird—as it has been incorrectly considered—but a =mammal=. The fur is

often of a bright chestnut colour. The ears are large and practically

devoid of hair, and are so thin as to be almost transparent. The wings

are thin folds of skin, which are attached in front to the long arms,

are supported by the greatly elongated fingers, and reach to the hind

limbs. Another membrane passes between the hind limbs, and in common

species is also supported by the tail. The thumb is free, and bears a

claw which is of some assistance in climbing. The hind limbs are small.

The structure of the bat is obviously but little adapted to walking,

and the animal moves about very awkwardly when on the ground, although

it can rise on the wing again without much difficulty.

The bat is rarely to be seen abroad after the middle of November, for

as the cold weather approaches and insects become scarce, it suspends

itself by its hind claws in some dark and sheltered corner, and goes to

sleep for the winter, reappearing in early spring.

50. HOOFED MAMMALS.

1. =The external characters of the sheep.=—(_a_) _Wool._—How does the

covering of a sheep’s body differ from the fur of a cat or rabbit,

and from the hair of the dog? Examine a lock of “raw” wool; is it at

all greasy? Dip it in water; is it much wetted? Are the fibres easily

entangled together? Why is woollen clothing so warm?

(_b_) _Teeth._—Obtain a sheep’s head from the butcher, and examine the

teeth. Notice the absence of incisors and canines in the upper jaw, and

of canines in the lower jaw. Observe the thickened pad on the surface

of the upper jaw, against which the lower incisors bite. Are the cheek

teeth flat, or sharp-edged like the cheek teeth of carnivores? Watch a

sheep feeding, and notice how it bites the grass. How is the lower jaw

moved during the chewing of the cud?

(_c_) _Horns._—Which sheep have the largest horns, the males (rams) or

the females (ewes)? If you can find a cast horn notice whether it is

hollow or solid. What is the use of horns?

(_d_) _Limbs._—Is there any marked difference in the lengths of fore

and hind limbs? Notice the _hoofs_ which cover those parts of the feet

touching the ground. How many hoofs are there on each foot?

2. =The habits of the sheep.=—Are sheep solitary or do they live in

flocks? What kind of ground do they seem to prefer, flat or hilly? Are

sheep on a hillside easily seen from a distance? Why not? Are sheep

nimble or clumsy? Can they run very fast? Would a flock of sheep be

safer from, say, wolves on a rocky hillside or on an open plain? In a

grazing flock of sheep notice whether most of the animals have their

heads turned in the same direction. Has the direction any relation to

the direction of the wind? Can you explain this?

In a running flock of sheep does any one animal act as leader? Is the

leader a ram or a ewe? Is it a lamb or an old animal? Do the rest of

the flock imitate the actions of the leader, and, for example, leap

over a wall at the same place in single file? Have you ever noticed

that if one animal jumps at a certain place, all the following sheep

jump at the same place? Have you ever seen sheep fighting? Were the

combatants rams or ewes? How did they fight?

What is the voice of a sheep like?

3. =Lambs.=—(_a_) _Appearance._—At what time of the year are lambs

born? Are they helpless or active? Have they long legs? What advantage

to the lamb is length of limb?

(_b_) _Play._—Watch lambs playing. Do they show a preference for any

eminence, _e.g._ a rock, in the neighbourhood? What is the meaning of

this preference? How do lambs fight? Have you ever seen a ewe stamp

with her fore-feet when anyone approached her lamb? At what age is a

sheep full grown?

=The sheep.=—The sheep (Fig. 173) differs in several important respects

from any of the animals previously mentioned. It is of course a mammal,

for it suckles its young, and its body is covered by hair; but the hair

is of that warm fleecy kind which is called =wool=. The fibres of wool

are seen under the microscope to be rough and scaly. For this reason

they can be spun into loosely-textured threads which entangle a great

deal of air; woollen garments are thus very bad conductors of heat. The

wool upon the sheep’s body is slightly greasy, from a substance which

is given off by the skin and protects the animal from rain. The toes

of the sheep are not armed with ordinary nails or claws, but claws are

represented by horny masses called =hoofs=, which encase the ends of

the toes, and upon which the whole weight of the body is thrown. The

sheep, especially the male (ram), is often provided with weapons in the

form of hollow =horns=, which grow upon its forehead.

[Illustration: FIG. 173.—Sheep.]

[Illustration: FIG. 174.—Section of Skull of Sheep. (After Flower.)]

[Illustration: FIG. 175.—Stomach of a Ruminant opened to show the

internal structure. For description, see text.]

=Method of feeding.=—The sheep is a strict vegetarian, living largely

upon grass. It grips the grass between its lower incisor teeth and a

hard pad on the upper jaw; there are no incisor teeth in the upper

jaw. Neither upper nor lower jaw bears canine teeth; and the cheek

teeth, which are used for chewing the food, have their crowns ridged

lengthwise. The arrangement of the teeth of the sheep is shown in Fig.

174. During grazing, however, the food is not at once chewed, but

is simply mixed with a large quantity of saliva and swallowed, the

chewing-process being performed at a later period. It is obviously a

great advantage to an animal, which in the wild state is liable at any

moment to be attacked by enemies, to be able to stow away its food

quickly, and afterwards masticate it at leisure. This is rendered

possible, in oxen, sheep, goats, deer, and the few other animals which

chew the cud, by the peculiar form of stomach shown in Fig. 175. The

hastily swallowed food is passed into the large paunch _b_ and into the

compartment _c_. When the animal finds an opportunity of “ruminating”

or chewing the cud, the food is returned to the mouth in small

quantities at a time, and is there finely divided by the cheek teeth.

In this condition it is again swallowed, and makes its way at once into

the compartment _d_, where it is strained between leaf-like folds and

then passed into the last chamber _e_, and thence to the intestines, to

undergo the final processes of digestion.

=Ruminants.=—Animals which, like the sheep, oxen, goats, deer, etc.,

ruminate or chew the cud in this manner, are called =ruminants=. In

all ruminants the weight of the body is supported by the tips of the

third and fourth toes of the feet, the remaining toes either having

completely disappeared or remaining very small (Fig. 176). The tips of

the toes are encased in horny hoofs, which represent greatly enlarged

claws or nails. The ruminants therefore belong to what may be called

the =even-toed hoofed mammals=. Pigs are also even-toed hoofed mammals,

but they are not ruminants, because, having simple stomachs, they do

not chew the cud.

[Illustration: FIG. 176.—Bones of fore-foot of Red Deer. (After

Flower.)]

[Illustration: FIG. 177.—Bones of fore-foot of Horse. (After Flower.)]

=Other hoofed mammals.=—In the horse and donkey the reduction of the

number of toes has gone still further; for these animals have now only

the third or middle toe of each foot left (Fig. 177); and because it

has to carry the whole weight of the body, it has become very large and

stout; its tip is encased in a hoof.

The =hoofed mammals= are therefore divided into two groups:

(1) the _odd-toed_, including the horse and ass (they have simple

stomachs, and therefore do not chew the cud); and

(2) the _even-toed_, including (_a_) ruminants like the sheep, etc.,

and (_b_) such non-ruminants as the pigs and their relatives.

=The inherited habits of the sheep.=—As in the cases of the dog and

cat, so in the sheep, the true explanation of several curious habits is

to be found in the manner of life of the wild ancestors; for it must

be remembered that domestication, however kindly an animal may take

to it, is an artificial condition of life. Wild sheep live in flocks,

as a rule in cold and mountainous districts; and some organisation is

necessary if they are not to be at the mercy of savage carnivores. An

old and experienced ram is generally in charge of the flock, and in

case of alarm he leads the way to a more inaccessible position. The

rest of the flock follow in single file, closely imitating his every

movement, leaping without hesitation—and therefore saving valuable

time—wherever he has leapt. The survival of this instinct in domestic

sheep may be observed whenever a flock is travelling along the road.

Even young lambs still display a decided preference for rocks,

hillocks, and other elevated positions. Wild sheep, being so liable

to sudden interruption when grazing, are enabled by their compound

stomachs to swallow food quickly and postpone the chewing process to a

more favourable opportunity. Sentinels usually keep watch, and warn the

flock of approaching enemies by stamping their hoofs on the ground, an

action which may still be seen whenever a ewe fears danger to her lambs.

=The play and education of the young.=—The young of mammals are usually

under the care of the mother for education and protection until they

are nearly adult; and it is generally found that the longest infancy

(in proportion to the natural life of the animal) occurs in the most

intelligent races. The importance of the play and education period

is very great, for it not only gives the young animal an opportunity

of training its natural faculties in comparative safety, by exercise

of various kinds and by games with companions of its own age and

strength; but it allows the mother to impart, by direct instruction,

some of the experience which she has personally gained during her

life. The extent of this maternal education is greater than has been

generally supposed; and every opportunity should be taken of observing

and recording cases of it.[15]

The play of young animals also in many cases gives important clues to

lost ancestral habits, which are not now to be seen in adult life. The

inherited tendency of animals to repeat, during their own development,

the history of their race is very great; some striking cases of this

will be considered in later chapters.

EXERCISES ON CHAPTER XIV.

1. Make a list of cases which you have observed of

protective colouration in mammals, specifying (_a_) the

colour of the animal, (_b_) the colour of its surroundings.

2. Describe any cases which you have observed of mammals

having differently-coloured coats in summer and winter. Of

what use is the change in colour?

3. Make a list of the mammals you know from observation to

walk (_a_) flat-footed, (_b_) on their toes, (_c_) on the

tips of their toes.

4. Make a list of the mammals which habitually hop, walk,

fly, and swim respectively; and find out, by observation

if possible, how the structure is adapted to the method of

life.

5. Study the habits of the mole, and try to discover by what

modifications it is enabled to burrow so rapidly.