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PATHFINDER PHYSIOLOGY No. 3
HYGIENIC PHYSIOLOGY
WITH SPECIAL REFERENCE TO THE USE OF
ALCOHOLIC DRINKS AND NARCOTICS
BEING A REVISED EDITION OF THE
FOURTEEN WEEKS IN HUMAN PHYSIOLOGY
BY JOEL DORMAN STEELE, PH.D.
ENLARGED EDITION WITH SELECTED READINGS
_Edited for the use of Schools, in accordance with the recent
Legislation upon Temperance Instruction_
INDORSEMENT.
BOSTON, _June_ 20, 1889.
The Pathfinder Series of Text-books on Anatomy, Physiology, and Hygiene
consists of the following volumes:
I. Child's Health Primer (for Primary Grades).
II. Hygiene for Young People or, Young People's Physiology. (for
Intermediate Classes)
III. Hygienic Physiology (for Advanced Pupils).
The above are the series originally prepared (as their general title
indicates) to supply the demand created by the laws for temperance
instruction in public schools in the United States. They were written by
experts under the supervision of the Scientific Department of the National
Woman's Christian Temperance Union, published by the instigation of the
same, and have been carefully revised from time to time, under the same
supervision, to keep them abreast with the latest teachings of science.
Being both teachable and well adapted to grade, their educational value,
as proven by schoolroom tests, is of the highest order. We therefore
cordially indorse and highly recommend the Pathfinder Series for use in
schools.
MARY H. HUNT,
_National and International Superintendent of the Scientific Dep't of
the Woman's Christian Temperance Union; Life Director of the National
Educational Association._
ADVISORY BOARD:
JOSEPH COOK, WILLIAM E. SHELDON, ALBERT H. PLUMB, D.D., DANIEL DORCHESTER,
D.D.
PREFACE
The term Physiology, or the science of the functions of the body, has come
to include Anatomy, or the science of its structure, and Hygiene, or the
laws of health; the one being essential to the proper understanding of
physiology, and the other being its practical application to life. The
three are intimately blended, and in treating of the different subjects
the author has drawn no line of distinction where nature has made none.
This work is not prepared for the use of medical students, but for the
instruction of youth in the principles which underlie the preservation of
health and the formation of correct physical habits. All else is made
subservient to this practical knowledge. A simple scientific dress is used
which, while conducing to clearness, also gratifies that general desire of
children to know something of the nomenclature of any study they pursue.
To the description of each organ is appended an account of its most common
diseases, accidents, etc., and, when practicable, their mode of treatment.
A pupil may thus learn, for example, the cause and cure of "a cold," the
management of a wound, or the nature of an inflammation.
The Practical Questions, which have been a prominent feature in other
books of the series, will be found, it is hoped, equally useful in this
work. Directions for preparing simple microscopic objects, and
illustrations of the different organs, are given under each subject.
The Readings, which represent the ideas but not always the exact
phraseology of the author quoted, have, in general, been selected with
direct reference to Practical Hygiene, a subject which now largely
occupies the public mind. The dangers that lurk in foul air and
contaminated water, in bad drainage, leaky gas pipes, and defective
plumbing, in reckless appetites, and in careless dissemination of
contagious diseases, are here portrayed in such a manner as, it is
trusted, will assist the pupil to avoid these treacherous quicksands, and
to provide for himself a solid path of health.
Under the heading of Health and Disease will be found Hints about the sick
room, Directions for the use of Disinfectants, Suggestions as to what to
do "Till the Doctor comes," and a list of antidotes for Poisons. Questions
for Class Use, a full Glossary, and an ample Index complete the book.
Believing in a Divine Architect of the human form, the author can not
refrain from occasionally pointing out His inimitable workmanship, and
impressing the lesson of a Great Final Cause.
The author has gleaned from every field, at home and abroad, to secure
that which would interest and profit his pupils. In general, Flint's great
work on the "Physiology of Man," an undisputed authority on both sides of
the Atlantic, has been adopted as the standard in digestion, respiration,
circulation, and the nervous system. Leidy's "Human Anatomy," and Sappey's
"Traité d'Anatomie" have been followed on all anatomical questions, and
have furnished many beautiful drawings. Huxley's "Physiology" has afforded
exceedingly valuable aid. Foster's "Text-Book of Physiology," Hinton's
"Health and its Conditions," Black's "Ten Laws of Health," Williams's
practical essay on "Our Eyes and How to Use them," Le Pileur's charming
treatise on "The Wonders of the Human Body," and that quaint volume, "Odd
Hours of a Physician," have aided the author with facts and fancies. The
writings of Draper, Dalton, Carpenter, Yalentin, Mapother, Watson,
Lankester, Letheby, Hall, Hamilton, Bell, Wilson, Bower, Cutter,
Hutchison, Wood, Bigelow, Stille, Holmes, Beigel, and others have been
freely consulted.
PUBLISHERS' NOTE.
An ABRIDGED EDITION of this work is published, to afford a cheaper manual
--adapted to Junior Classes and Common Schools. The abridgment contains
the essence of this text, nearly all its illustrations, and the whole of
the Temperance matter as here presented.
ORDER "HYGIENIC PHYSIOLOGY, ABRIDGED."
READING REFERENCES.
Foster's "Text-Book of Physiology"; Leidy's "Human Anatomy"; Draper's
"Human Physiology"; Dalton's "Physiology and Hygiene"; Cutter's
"Physiology"; Johnston and Church's "Chemistry of Common Life"; Letheby's
"Food"; Tyndall "On Light," and "On Sound"; Mint's "Physiology of Man ";
Rosenthal's "Physiology of the Muscles and Nerves"; Bernstein's "Five
Senses of Man"; Huxley and Youmans's "Physiology and Hygiene"; Sappey's
"Traité d'Anatomie "; Luys's "Brain and its Functions"; Smith's "Foods";
Bain's "Mind and Body"; Pettigrew's "Animal Locomotion"; Carpenter's
"Human Physiology," and "Mental Physiology"; Wilder and Gage's "Anatomy";
Jarvis's "Physiology and Laws of Health."
Hargreaves's "Alcohol and Science"; Richardson's "Ten Lectures on
Alcohol," and "Diseases of Modern Life"; Brown's "Alcohol"; Davis's
"Intemperance and Crime"; Pitman's "Alcohol and the State"; "Anti-
Tobacco"; Howie's "Stimulants and Narcotics"; Hunt's "Alcohol as Food or
Medicine"; Schützenberger's "Fermentation"; Hubbard's "Opium Habit and
Alcoholism"; Trouessart's "Microbes, Ferments, and Molds."
CONTENTS
INTRODUCTION
I.--THE SKELETON
THE HEAD
THE TRUNK
THE LIMBS
II.--THE MUSCLES
III.--THE SKIN
THE HAIR AND THE NAILS
THE TEETH
IV.--RESPIRATION AND THE VOICE
V.--THE CIRCULATION
THE BLOOD
THE HEART
THE ARTERIES
THE VEINS
VI.--DIGESTION AND FOOD
VII.--THE NERVOUS SYSTEM
THE BRAIN
THE SPINAL CORD AND THE NERVES
THE SYMPATHETIC SYSTEM
VIII.--THE SPECIAL SENSES
TOUCH
TASTE
SMELL
HEARING
SIGHT
IX.--HEALTH AND DISEASE.--DEATH AND DECAY
1. HINTS ABOUT THE SICK ROOM
2. DISINFECTANTS
3. WHAT TO DO "TILL THE DOCTOR COMES"
4. ANTIDOTES TO POISONS
X.--SELECTED READINGS
XI.--APPENDIX
QUESTIONS FOR CLASS USE
GLOSSARY
INDEX
SUGGESTIONS To Teachers
Seeing is believing--more than that, it is often knowing and remembering.
The mere reading of a statement is of little value compared with the
observation of a fact. Every opportunity should therefore be taken of
exhibiting to the pupil the phenomena described, and thus making them
real. A microscope is so essential to the understanding of many subjects,
that it is indispensable to the proper teaching of Physiology. A suitable
instrument and carefully prepared specimens, showing the structure of the
bones, the skin, and the blood of various animals, the pigment cells of
the eye, etc., may be obtained at a small cost from any good optician.
On naming the subject of a paragraph, the pupil should be prepared to tell
all he knows about it. No failure should discourage the teacher in
establishing this mode of study and recitation. A little practice will
produce the most satisfactory results. The unexpected question and the apt
reply develop a certain sharpness and readiness which are worthy of
cultivation. The questions for review, or any others that the wit of the
teacher may suggest, can be effectively used to break the monotony of a
topical recitation, thereby securing the benefits of both systems.
The pupil should expect to be questioned each day upon any subject passed
over during the term, and thus the entire knowledge gained will be within
his grasp for instant use. While some are reciting to the teacher, let
others write on slates or on the blackboard. At the close of the
recitation, let all criticise the ideas, the spelling, the use of
capitals, the pronunciation, the grammar, and the mode of expression.
Greater accuracy and much collateral drill may thus be secured at little
expense of valuable school time.
The Introduction is designed merely to furnish suggestive material for the
first lesson, preparatory to beginning the study. Other subjects for
consideration may be found in the section on Health and Disease, in the
Selected Readings, and among the questions given in the Appendix. Where
time will allow, the Selected Readings may profitably be used in
connection with the topics to which they relate. Questions upon them are
so incorporated with those upon the text proper that they may be employed
or not, according to the judgment of the teacher.
NOTE.--Interest in the study of Physiology will be much increased by the
use of the microscope and prepared slides. These may be obtained from any
good optician.
INTRODUCTION.
Physiological study in youth is of inestimable value. Precious lives are
frequently lost through ignorance. Thousands squander in early years the
strength which should have been kept for the work of real life. Habits are
often formed in youth which entail weakness and poverty upon manhood, and
are a cause of lifelong regret. The use of a strained limb may permanently
damage it. Some silly feat of strength may produce an irreparable injury.
A thoughtless hour of reading by twilight may impair the sight for life. A
terrible accident may happen, and a dear friend perish before our eyes,
while we stand by powerless to render the assistance we could so easily
give did we "only know what to do." The thousand little hints which may
save or lengthen life, may repel or abate disease, and the simple laws
which regulate our bodily vigor, should be so familiar that we may be
quick to apply them in an emergency. The preservation of health is easier
than the cure of disease. Childhood can not afford to wait for the lesson
of experience which is learned only when the penalty of violated law has
been already incurred, and health irrevocably lost.
NATURE'S LAWS INVIOLABLE.--In infancy, we learn how terribly Nature
punishes a violation of certain laws, and how promptly she applies the
penalty. We soon find out the peril of fire, falls, edged tools, and the
like. We fail, however, to notice the equally sharp and certain
punishments which bad habits entail. We are quick to feel the need of
food, but not so ready to perceive the danger of an excess. A lack of air
drives us at once to secure a supply; foul air is as fatal, but it gives
us no warning.
Nature provides a little training for us at the outset of life, but leaves
the most for us to learn by bitter experience. So in youth we throw away
our strength as if it were a burden of which we desire to be rid. We eat
anything, and at any time; do anything we please, and sit up any number of
nights with little or no sleep. Because we feel only a momentary
discomfort from these physical sins, we fondly imagine when that is gone
we are all right again. Our drafts upon our constitution are promptly
paid, and we expect this will always be the case; but some day they will
come back to us, protested; Nature will refuse to meet our demands, and we
shall find ourselves physical bankrupts.
We are furnished in the beginning with a certain vital force upon which we
may draw. We can be spendthrifts and waste it in youth, or be wise and so
husband it till manhood. Our shortcomings are all charged against this
stock. Nature's memory never fails; she keeps her account with perfect
exactness. Every physical sin subtracts from the sum and strength of our
years. We may cure a disease, but it never leaves us as it found us. We
may heal a wound, but the scar still shows. We reap as we sow, and we may
either gather in the thorns, one by one, to torment and destroy, or we may
rejoice in the happy harvest of a hale old age.
I.
THE SKELETON.
"Not in the World of Light alone,
Where God has built His blazing throne,
Nor yet alone on earth below,
With belted seas that come and go,
And endless isles of sunlit green
Is all thy Maker's glory seen--
Look in upon thy wondrous frame,
Eternal wisdom still the same!"
HOLMES.
ANALYSIS OF THE SKELETON.
NOTE.--The following Table of 206 bones is exclusive of the 8 sesamoid
bones which occur in pairs at the roots of the thumb and great toe, making
214 as given by Leidy and Draper. Gray omits the bones of the ear, and
names 200 as the total number.
THE SKELETON.
_
| I. THE HEAD (_28 bones._)
| _
| | Frontal Bone (forehead).
| _ | Two Parietal Bones.
| | 1. CRANIUM..............| Two Temporal (temple) Bones.
| | (_8 bones._) | Sphenoid Bone.
| | | Ethmoid (sieve-like bone at root of nose).
| | |_Occipital Bone (back and base of skull).
| | _
| | | Two Superior Maxillary (upper jaw) Bones.
| | | Inferior Maxillary (lower jaw) Bone.
| | | Two Malar (cheek) Bones.
| | 2. FACE.................| Two Lachrymal Bones.
| | (_14 bones._) | Two Turbinated (scroll like) Bones, each
| | | side of nose.
| | | Two Nasal Bones (Bridge of nose).
| | | Vomer (the bone between the nostrils).
| | |_Two Palate Bones.
| | _
| | | Hammer.
| | 3. EARS.................| Anvil.
| |_ (_6 bones._) |_Stirrup.
|
| II. THE TRUNK (_54 bones._)
| _
| | Cervical Vertebræ (seven vertebræ of the
| _ | neck).
| | 1. SPINAL COLUMN........| Dorsal Vertebræ (twelve vertebræ of the
| | | back).
| | | Lumbar Vertebræ (five vertebræ of the
| | |_ loins).
| | _
| | | True Ribs.
| | 2. RIBS.................|_False Ribs.
| |
| | 3. STERNUM (breastbone).
| |
| | 4. OS HYOIDES (bone at the root of tongue).
| | _
| | | Two Innominata.
| |_5. PELVIS...............| Sacrum.
| |_Coccyx.
|
| III. THE LIMBS (_124 bones._)
| _
| _ | _Clavicle._
| | Shoulder...|__Scapula._
| _ | _
| | 1. UPPER LIMBS..........| | _Humerus._
| | (_64 bones._) | Arm........|__Ulna and Radius._
| | | _
| | | | _Eight Wrist or Carpal
| | | | Bones._
| | |_Hand.......| _Five Metacarpal Bones._
| | |__Phalanges (14 bones)._
| | _
| | _ | _Femur._
| | | Leg........| _Patella._
| | | |__Tibia and Fibula._
| | 2. LOWER LIMBS..........| _
| |_ (_60 bones._) | | _Seven Tarsal Bones._
|_ | Foot.......| _Five Metatarsal Bones._
|_ |__Phalanges (14 bones)._
_
| 1. Uses.
_ | 2. Composition.
| 1. FORM, STRUCTURE, | 3. Structure.
| ETC., OF THE BONES | 4. Growth.
| | 5. Repair.
THE SKELETON | |_6. The Joints.
| _
| 2. CLASSIFICATION OF | 1. The Head.
|_ THE BONES. | 2. The Trunk.
|_3. The Limbs.
THE SKELETON.
I. FORM, STRUCTURE, ETC., OF THE BONES.
(_See page 269_.)
THE SKELETON, or framework of the "House we live in," is composed of about
200 bones. [Footnote: The precise number varies in different periods of
life. Several which are separated in youth become united in old age. Thus
five of the "false vertebræ" at the base of the spine early join in one
great bone--the sacrum; while four tiny ones below it often run into a
bony mass--the coccyx (Fig. 6); in the child, the sternum is composed of
eight pieces, while in the adult it consists of only three. While,
however, the number of the bones is uncertain, their relative length is so
exact that the length of the entire skeleton, and thence the height of the
man, can be obtained by measuring a single one of the principal bones.
Fossil bones and those found at Pompeii have the same proportion as our
own.]
USES AND FORMS OF THE BONES.--They have three principal uses: 1. To
protect the delicate organs; [Footnote: An organ is a portion of the body
designed for a particular use, called its _function_. Thus the heart
circulates the blood; the liver produces the bile.] 2. To serve as levers
on which the muscles may act to produce motion; and 3. To preserve the
shape of the body.
Bones differ in form according to the uses they subserve. For convenience
in walking, some are long; for strength and compactness, some are short
and thick; for covering a cavity, some are flat; and for special purposes,
some are irregular. The general form is such as to combine strength and
lightness. For example, all the long bones of the limbs are round and
hollow, thus giving with the same weight a greater strength, [Footnote:
Cut a sheet of foolscap in two pieces. Roll one half into a compact
cylinder, and fold the other into a close, flat strip; support the ends of
each and hang weights in the middle until they bend. The superior strength
of the roll will astonish one unfamiliar with this mechanical principle.
In a rod, the particles break in succession, first those on the outside,
and later those in the center. In a tube, the particles are all arranged
where they resist the first strain. Iron pillars are therefore cast
hollow. Stalks of grass and grain are so light as to bend before a breath
of wind, yet are stiff enough to sustain their load of seed. Bone has been
found by experiment to possess twice the resisting property of solid oak.]
and also a larger surface for the attachment of the muscles.
The Composition of the Bones at maturity is about one part animal to two
parts mineral matter. The proportion varies with the age. In youth it is
nearly half and half, while in old age the mineral is greatly in excess.
By soaking a bone in weak muriatic acid, and thus dissolving the mineral
matter, its shape will not change, but its stiffness will disappear,
leaving a tough, gristly substance [Footnote: Mix a wineglass of muriatic
acid with a pint of water, and place in it a sheep's rib. In a day or two,
the bone will become so soft that it can be tied into a knot. In the same
way, an egg may be made so pliable that it can be crowded into a narrow-
necked bottle, within which it will expand, and become an object of great
curiosity to the uninitiated. By boiling bones at a high temperature, the
animal matter separates in the form of gelatine. Dogs and cats extract the
animal matter from the bones they eat. Fossil bones deposited in the
ground during the Geologic period, were found by Cuvier to contain
considerable animal matter. Gelatine was actually extracted from the
Cambridge mastodon, and made into glue. A tolerably nutritious food might
thus be manufactured from bones older than man himself.] (cartilage) which
can be bent like rubber.
If the bone be burned in the fire, thus consuming the animal matter, the
shape will still be the same, but it will have lost its tenacity, and the
beautiful, pure-white residue [Footnote: From bones thus calcined, the
phosphorus of the chemist is made. See Steele's "Popular Chemistry," page
114. If the animal matter be not consumed, but only charred, the bone will
be black and brittle. In this way, the "boneblack" of commerce is
manufactured.] may be crumbled into powder with the fingers.
FIG. 2.
[Illustration: _The Thigh Bone, or Femur, sawed lengthwise._]
We thus see that a bone receives hardness and rigidity from its mineral,
and tenacity and elasticity from its animal matter.
The entire bone is at first composed of cartilage, which gradually
_ossifies_ or turns to bone. [Footnote: The ossification of the bones
on the sides and upper part of the skull, for example, begins by a rounded
spot in the middle of each one. From this spot the ossification extends
outward in every direction, thus gradually approaching the edges of the
bone. When two adjacent bones meet, there will be a line where their edges
are in contact with each other, but have not yet united; but when more
than two bones meet in this way, there will be an empty space between them
at their point of junction. Thus, if you lay down three coins upon the
table with their edges touching one another, there will be a three-sided
space in the middle between them; if you lay down four coins in the same
manner, the space between them will be four-sided. Now at the back part of
the head there is a spot where three bones come together in this way,
leaving a small, three-sided opening between them: this is called the
"posterior fontanelle." On the top of the head, four bones come together,
leaving between them a large, four-sided opening: this is called the
"anterior fontanelle." These openings are termed the _fontanelles_,
because we can feel the pulsations of the brain through them, like the
bubbling of water in a fountain. They gradually diminish in size, owing to
the growth of the bony parts around them, and are completely closed at the
age of four years after birth.--DALTON.] Certain portions near the joints
are long delayed in this process, and by their elasticity assist in
breaking the shock of a fall. [Footnote: Frogs and toads, which move by
jumping, and consequently receive so many jars, retain these unossified
portions (epiphyses) nearly through, life, while alligators and turtles
whose position is sprawling, and whose motions are measured do not have
them at all--LEIDY] Hence the bones of children are tough, are not readily
fractured, and when broken easily heal again; [Footnote: This is only one
of the many illustrations of the Infinite care that watches over helpless
infancy, until knowledge and ability are acquired to meet the perils of
life.] while those of elderly people are liable to fracture, and do not
quickly unite.
FIG. 3.
[Illustration: _A thin slice of Bone, highly magnified showing the
lacunæ, the tiny tubes (canaliculi) radiating from them, and four
Haversian canals, three seen crosswise and one lengthwise._]
THE STRUCTURE OF THE BONES--When a bone is sawed lengthwise, it is found
to be a compact shell filled with a spongy substance This filling
increases in quantity, and becomes more porous at the ends of the bone,
thus giving greater size to form a strong joint, while the solid portion
increases near the middle, where strength alone is needed. Each fiber of
this bulky material diminishes the shock of a sudden blow, and also acts
as a beam to brace the exterior wall. The recumbent position of the
alligator protects him from falls, and therefore his bones contain very
little spongy substance.
In the body, bones are not the dry, dead, blanched things they commonly
seem to be, but are moist, living, pinkish structures, covered with a
tough membrane, called the per-i-os'-te-um [Footnote: The relations of the
periosteum to the bone are very interesting. Instances are on record where
the bone has been removed, leaving the periosteum, from which the entire
bone was afterward renewed.] (_peri_, around, and _osteon_, a
bone), while the hollow is filled with marrow, rich in fat, and full of
blood vessels. If we examine a thin slice with the microscope, we shall
see black spots with lines running in all directions, and looking very
like minute insects. These are really little cavities, called la-cu'-næ
[Footnote: When the bone is dry, the lacunæ are filled with air, which
refracts the light, so that none of it reaches the eye, and hence the
cavities appear black.] from which radiate tiny tubes. The lacunæ are
arranged in circles around larger tubes, termed from their discoverer,
_Haversian canals_, which serve as passages for the blood vessels
that nourish the bone.
GROWTH OF THE BONES.--By means of this system of canals, the blood
circulates as freely through the bones as through any part of the body,
The whole structure is constantly but slowly changing, [Footnote: Bone is
sometimes produced with surprising rapidity. The great Irish Elk is
calculated by Prof. Owen to have cast off and renewed, annually in its
antlers eighty pounds of bone.] old material being taken out and new put
in. A curious illustration is seen in the fact that if madder be mixed
with the food of pigs, it will tinge their bones red.
REPAIR OF THE BONES.--When a bone is broken, the blood at once oozes out
of the fractured ends. This soon gives place to a watery fluid, which in a
fortnight thickens to a gristly substance, strong enough to hold them in
place. Bone matter is then slowly deposited, which in five or six weeks
will unite the broken parts. Nature, at first, apparently endeavors to
remedy the weakness of the material by excess in the quantity, and so the
new portion is larger than the old. But the extra matter will be gradually
absorbed, sometimes so perfectly as to leave no trace of the injury. (See
p. 271.)
A broken limb should be held in place by splints, or a plaster cast, to
enable this process to go on uninterruptedly, and also lest a sudden jar
might rupture the partially mended break. For a long time, the new portion
consists largely of animal matter, and so is tender and pliable. The
utmost care is therefore necessary to prevent a malformation.
THE JOINTS are packed with a soft, smooth cartilage, or gristle, which
fits so perfectly as to be airtight. Upon convex surfaces, it is thickest
at the middle, and upon concave surfaces, it is thickest at the edge, or
where the wear is greatest. In addition, the ends of the bones are covered
with a thin membrane, the _synovial_ (_sun_, with; _ovum_,
an egg), which secretes a viscid fluid, not unlike the white of an egg.
This lubricates the joints, and prevents the noise and wear of friction.
The body is the only machine that oils itself.
The bones which form the joint are tied with stout ligaments (_ligo_,
I bind), or bands, of a smooth, silvery white tissue, [Footnote: The
general term _tissue_ is applied to the various textures of which the
organs are composed. For example, the osseous tissue forms the bones; the
fibrous tissue, the skin, tendons, and ligaments.] so strong that the
bones are sometimes broken without injuring the fastenings.
II. CLASSIFICATION OF THE BONES.
For convenience, the bones of the skeleton are considered in three
divisions: the _head_, the _trunk_, and the _limbs_.
1. THE HEAD.
THE BONES OF THE SKULL AND THE FACE form a cavity for the protection of
the brain and the four organs of sense, viz.: sight, smell, taste, and
hearing. All these bones are immovable except the lower jaw, which is
hinged [Footnote: A ring of cartilage is inserted in its joints, something
after the manner of a washer in machinery. This follows the movements of
the jaw, and admits of freer motion, while it guards against dislocation.]
at the back so as to allow for the opening and shutting of the mouth.
THE SKULL is composed, in general, of two compact plates, with a spongy
layer between. These are in several pieces, the outer ones being joined by
notched edges, sutures (su'tyurs,), in the way carpenters term
dovetailing. (See Fig. 4.)
FIG. 4.
[Illustration: _The Skull._--1. _frontal bone;_ 2, _parietal bone;_
3, _temporal bone;_ 4, _the sphenoid bone;_ 5, _ethmoid bone;_ 6,
_superior maxillary (upper jaw) bone;_ 7, _malar bone;_ 8, _lachrymal
bone;_ 9, _nasal bone;_ 10, _inferior maxillary (lower jaw) bone._]
The peculiar structure and form of the skull afford a perfect shelter for
the brain--an organ so delicate that, if unprotected, an ordinary blow
would destroy it. Its oval or egg shape adapts it to resist pressure. The
smaller and stronger end is in front, where the danger is greatest.
Projections before and behind shield the less protected parts. The hard
plates are not easy to penetrate. [Footnote: Instances have been known
where bullets, striking against the skull, have glanced off, been
flattened, or even split into halves. In the Peninsular Campaign, the
author saw a man who had been struck in the forehead by a bullet which,
instead of penetrating the brain, had followed the skull around to the
back of the head, and there passed out.] The spongy packing deadens every
blow. [Footnote: An experiment resembling the familiar one of the balls in
Natural Philosophy ("Steele's Popular Physics," Fig. 6, p. 26),
beautifully illustrates this point. Several balls of ivory are suspended
by cords, as in Fig. 5. If A be raised and then let fall, it will transmit
the force to B, and that to C, and so on until F is reached, which will
fly off with the impulse. If now a ball of spongy bone be substituted for
an ivory one anywhere in the line, the force will be checked, and the last
ball will not stir.] The separate pieces with their curious joinings
disperse any jar which one may receive, and also prevent fractures from
spreading.
FIG. 5.
[Illustration]
The frequent openings in this strong bone box afford safe avenues for the
passage of numerous nerves and vessels which communicate between the brain
and the rest of the body.
FIG. 6.
[Illustration: _The Spine; the seven vertebræ of the neck, cervical; the
twelve of the back, dorsal; the five of the loins, lumbar;_ a, _the
sacrum, and_ b, _the coccyx, coming the nine "false vertebræ."_
(p. 3).]
2 THE TRUNK.
THE TRUNK has two important cavities. The upper part, or _chest_,
contains the heart and the lungs, and the lower part, or _abdomen_,
holds the stomach, liver, kidneys, and other organs (Fig. 31). The
principal bones are those of the _spine_, the _ribs_, and the
_hips_.
THE SPINE consists of twenty-four bones, between which are placed pads of
cartilage. [Footnote: These pads vary in thickness from one fourth to one
half an inch. They become condensed by the weight they bear during the
day, so that we are somewhat shorter at evening than in the morning.
Their elasticity causes them to resume their usual size during the night,
or when we lie down for a time.] A canal is hollowed out of the column
for the safe passage of the spinal cord. (See Fig. 50.) Projections
(processes) at the back and on either side are abundant for the attachment
of the muscles. The packing acts as a cushion to prevent any jar from
reaching the brain when we jump or run, while the double curve of the
spine also tends to disperse the force of a fall. Thus on every side the
utmost caution is taken to guard that precious gem in its casket.
THE PERFECTION OF THE SPINE surpasses all human contrivances. Its various
uses seem a bundle of contradictions. A chain of twenty-four bones is made
so stiff that it will bear a heavy burden, and so flexible that it will
bend like rubber; yet, all the while, it transmits no shock, and even
hides a delicate nerve within that would thrill with the slightest touch.
Resting upon it, the brain is borne without a tremor; and, clinging to it,
the vital organs are carried without fear of harm.
FIG. 7.
[Illustration: B, _the first cervical vertebra, the atlas;_ A, _the
atlas, and the second cervical vertebra, the axis;_ e, _the odontoid
process;_ c, _the foramen._]
THE SKULL ARTICULATES with (is jointed to) the spine in a peculiar manner.
On the top of the upper vertebra (atlas [Footnote: Thus called because,
as, in ancient fable, the god Atlas supported the world on his shoulders,
so in the body this bone bears the head.]) are two little hollows
(_a_, _b_, Fig. 7), nicely packed and lined with the synovial
membrane, into which fit the corresponding projections on the lower part
of the skull, and thus the head can rock to and fro. The second vertebra
(axis) has a peg, _e_, which projects through a hole, _c_, in
the first.
FIG. 8.
[Illustration: _The Thorax or Chest._ a, _the sternum;_ b _to_ c, _the
true ribs;_ d _to_ h, _the false ribs;_ g, h, _the floating ribs;_ i, k,
_the dorsal vertebræ._]
The surfaces of both vertebræ are so smooth that they easily glide on each
other, and thus, when we move the head side wise, the atlas turns around
the peg, _e_, of the axis.
THE RIBS, also twenty-four in number, are arranged in pairs on each side
of the chest. At the back, they are all attached to the spine. In front,
the upper seven pairs are tied by cartilages to the breastbone (sternum);
three are fastened to each other and to the cartilage above, and two, the
floating ribs, are loose.
The natural form of the chest is that of a cone diminishing upward. But,
owing to the tightness of the clothing commonly worn, the reverse is often
the case. The long, slender ribs give lightness, [Footnote: If the chest
wall were in one bone thick enough to resist a blow, it would be unwieldy
and heavy As it is, the separate bones bound by cartilages yield
gradually, and diffuse the force among them all, and so are rarely
broken.] the arched form confers strength, and the cartilages impart
elasticity,--properties essential to the protection of the delicate organs
within, and to freedom of motion in respiration. (See note, p. 80.)
FIG. 9.
[Illustration: _The Pelvis._ a, _the sacrum;_ b, b, _the right
and the left innominatum._]
THE HIP BONES, called by anatomists the innominata, or nameless bones,
form an irregular basin styled the _pelvis_ (_pelvis_, a basin).
In the upper part, is the foot of the spinal column--a wedge-shaped bone
termed the _sacrum_ [Footnote: So called because it was anciently
offered in sacrifice.] (sacred), firmly planted here between the
widespreading and solid bones of the pelvis, like the keystone to an arch,
and giving a steady support to the heavy burden above.
3. THE LIMBS.
TWO SETS OF LIMBS branch from the trunk, viz.: the upper, and the lower.
They closely resemble each other. The arm corresponds to the thigh; the
forearm, to the leg; the wrist, to the ankle; the fingers, to the toes.
The fingers and the toes are so much alike that they receive the same
name, _digits_, while the several bones of both have also the common
appellation, _phalanges_. The differences which exist grow out of
their varying uses. The foot is characterized by strength; the hand, by
mobility.
FIG. 10.
[Illustration: _The Shoulder Joint._ a, _the clavicle;_ b,
_the scapula._]
1. THE UPPER LIMBS.--THE SHOULDER.--The bones of the shoulder are the
collar bone (clavicle), and the shoulder blade (scapula). The
_clavicle_ (_clavis_, a key) is a long, slender bone, shaped
like the Italic _f_. It is fastened at one end to the breastbone and
the first rib, and, at the other, to the shoulder blade. (See Fig. 1.) It
thus holds the shoulder joint out from the chest, and gives the arm
greater play. If it be removed or broken, the head of the arm bone will
fall, and the motions of the arm be greatly restricted. [Footnote: Animals
which use the forelegs only for support (as the horse, ox, etc.), do not
possess this bone. "It is found in those that dig, fly, climb and seize."]
THE SHOULDER BLADE is a thin, flat, triangular bone, fitted to the top and
back of the chest, and designed to give a foundation for the muscles of
the shoulder.
THE SHOULDER JOINT.--The arm bone, or _humerus_, articulates with the
shoulder blade by a ball-and-socket joint. This consists of a cup-like
cavity in the latter bone, and a rounded head in the former, to fit it,--
thus affording a free rotary motion. The shallowness of the socket
accounts for the frequent dislocation of this joint, but a deeper one
would diminish the easy swing of the arm.
FIG. 11.
[Illustration: _Bones of the right Forearm._ H, _the humerus;_
R, _the radius; and_ U, _the ulna._]
THE ELBOW.--At the elbow, the humerus articulates with the _ulna_--a
slender bone on the inner side of the forearm--by a hinge joint which
admits of motion in only two directions, _i. e._, backward and
forward. The ulna is small at its lower end; the _radius_, or large
bone of the forearm, on the contrary, is small at its upper end, while it
is large at its lower end, where it forms the wrist joint. At the elbow,
the head of the radius is convex and fits into a shallow cavity in the
ulna, while at the wrist the ulna plays in a similar socket in the radius.
Thus the radius may roll over and even cross the ulna.
THE WRIST, or _carpus_, consists of two rows of very irregular bones,
one of which articulates with the forearm; the other, with the hand. They
are placed side to side, and so firmly fastened as to admit of only a
gliding motion. This gives little play, but great strength, elasticity,
and power of resisting shocks.
THE HAND.--The _metacarpal_ (_meta_, beyond; _karpos_,
wrist), or bones of the palm, support each a thumb or a finger. Each
finger has three bones, while the thumb has only two. The first bone of
the thumb, standing apart from the rest, enjoys a special freedom of
motion, and adds greatly to the usefulness of the hand.
FIG. 12.
[Illustration: _Bones of the Hand and the Wrist._]
The first bone (Figs. 11, 12) of each finger is so attached to the
corresponding metacarpal bone as to move in several directions upon it,
but the other phalanges form hinge joints.
The fingers are named in order: the thumb, the index, the middle, the
ring, and the little finger. Their different lengths cause them to fit the
hollow of the hand when it is closed, and probably enable us more easily
to grasp objects of varying size. If the hand clasps a ball, the tips of
the fingers will be in a straight line.
The hand in its perfection belongs only to man. Its elegance of outline,
delicacy of mold, and beauty of color have made it the study of artists;
while its exquisite mobility and adaptation as a perfect instrument have
led many philosophers to attribute man's superiority even more to the hand
than to the mind. [Footnote: How constantly the hand aids us in explaining
or enforcing a thought! We affirm a fact by placing the hand as if we
would rest it firmly on a body; we deny by a gesture putting the false or
erroneous proposition away from us; we express doubt by holding the hand
suspended, as if hesitating whether to take or reject. When we part from
dear friends, or greet them again after long absence, the hand extends
toward them as if to retain, or to bring them sooner to us. If a recital
or a proposition is revolting, we reject it energetically in gesture as in
thought. In a friendly adieu we wave our good wishes to him who is their
object; but when it expresses enmity, by a brusque movement we sever every
tie. The open hand is carried backward to express fear or horror, as well
as to avoid contact; it goes forward to meet the hand of friendship; it is
raised suppliantly in prayer toward Him from whom we hope for help; it
caresses lovingly the downy cheek of the infant, and rests on its head
invoking the blessing of Heaven,--_Wonders of the Human Body_.]
FIG. 13.
[Illustration: _The Mechanism of the Hip Joint._]
2. THE LOWER LIMBS.--THE HIP--The thigh bone, or _femur_, is the
largest and necessarily the strongest in the skeleton, since at every step
it has to bear the weight of the whole body. It articulates with the hip
bone by a ball-and-socket joint. Unlike the shoulder joint, the cup here
is deep, thus affording less play, but greater strength. It fits so
tightly that the pressure of the air largely aids in keeping the bones in
place. [Footnote: In order to test this, a hole was bored through a hip
bone, so as to admit air into the socket, the thigh bone at once fell out
as far as the ligaments would permit. An experiment was also devised
whereby a suitably prepared hip joint was placed under the receiver of an
air pump. On exhausting the air, the weight of the femur caused it to drop
out of the socket, while the readmission of the air raised it to its
place. Without this arrangement, the adjacent muscles would have been
compelled to bear the additional weight of the thighbone every time it was
raised. Now the pressure of the air rids them of this unnecessary burden,
and hence they are less easily fatigued--WEBER] Indeed, when the muscles
are cut away, great force is required to detach the limbs.
THE KNEE is strengthened by the patella_, or kneepan (_patella_,
little dish), a chestnut-shaped bone firmly fastened over the joint.
The shin bone, or _tibia_, the large, triangular bone on the inner
side of the leg, articulates both with the femur and the foot by hinge
joints. The kneejoint is so made, however, as to admit of a slight rotary
motion when the limb is not extended.
The _fibula_ (_fibula_, a clasp), the small, outside bone of the
leg, is firmly bound at each end to the tibia. (See Fig. 1.) It is
immovable, and, as the tibia bears the principal weight of the body, the
chief use of this second bone seems to be to give more surface to which
the muscles may be attached. [Footnote: A young man in the hospital at
Limoges had lost the middle part of his tibia. The lost bone was not
reproduced, but the fibula, the naturally weak and slender part of the
leg, became thick and strong enough to support the whole body.--STANLEY'S
_Lectures_.]
THE FOOT.--The general arrangement of the foot is strikingly like that of
the hand (Fig. 1). The several parts are the _tarsus_, the
_metatarsus_, and the _phalanges_. The graceful arch of the
foot, and the numerous bones joined by cartilages, give an elasticity to
the step that could never be attained by a single, flat bone. [Footnote:
The foot consists of an arch, the base of which is more extended in front
than behind, and the whole weight of the body is made to fall on this arch
by means of a variety of joints. These joints further enable the foot to
be applied, without inconvenience, to rough and uneven surfaces.--HINTON.]
The toes naturally lie straight forward in the line of the foot. Few
persons in civilized nations, however, have naturally formed feet. The big
toe is crowded upon the others, while crossed toes, nails grown-in,
enormous joints, corns, and bunions abound.
THE CAUSE OF THESE DEFORMITIES is found in the shape and size of
fashionable boots and shoes. The sole ought to be large enough for full
play of motion, the uppers should not crowd the toes, and the heels should
be low, flat, and broad. As it is, there is a constant warfare between
Nature and our shoemakers, [Footnote: When we are measured for boots or
shoes, we should stand on a sheet of paper, and have the shoemaker mark
with a pencil the exact outline of our feet as they bear our whole weight.
When the shoe is made, the sole should exactly cover this outline.] and we
are the victims. The narrow point in front pinches our toes, and compels
them to override one another; the narrow sole compresses the arch; while
the high heel, by throwing all the weight forward on the toes, strains the
ankle, and, by sending the pressure where Nature did not design it to
fall, causes that joint to become enlarged. The body bends forward to meet
the demand of this new motion, and thus loses its uprightness and beauty,
making our gait stiff and ungraceful. (See p. 271.)
DISEASES, ETC.--l. _Rickets_, a disease of early life, is caused by a
lack of mineral matter in the bones, rendering them soft and pliable, so
that they bend under the weight of the body. They thus become permanently
distorted, and of course are weaker than if they were straight, [Footnote:
Just here appears an exceedingly beautiful provision. As soon as the
disproportion of animal matter ceases, a larger supply of mineral is sent
to the weak points, and the bones actually become thicker, denser, harder,
and consequently stronger at the very concave part where the stress of
pressure is greatest.--WATSON'S _Lectures_. We shall often have
occasion to refer to similar wise and providential arrangements whereby
the body is enabled to remedy defects, and to prepare for accidents.]
Rickets is most common among children who have inherited a feeble
constitution and who are ill fed, or who live in damp, ill-ventilated
houses. "Rickety" children should have plenty of fresh air and sunlight,
nourishing food, comfortable clothing, and, in short, the best of hygienic
care.
2. _A Felon_ is a swelling of the finger or thumb, usually of the
last joint. It is marked by an accumulation beneath the periosteum and
next the bone. The physician will merely cut through the periosteum, and
let out the effete matter.
3. _Bowlegs_ are caused by children standing on their feet before the
bones of the lower limbs are strong enough to bear their weight. The
custom of encouraging young children to stand by means of a chair or the
support of the hand, while the bones are yet soft and pliable, is a cruel
one, and liable to produce permanent deformity. Nature will set the child
on its feet when the proper time comes.
4. _Curvature of the Spine_.--When the spine is bent, the packing
between the vertebræ becomes compressed on one side into a wedge-like
shape. After a time, it will lose its elasticity, and the spine will
become distorted. This often occurs in the case of students who bend
forward to bring their eyes nearer their books, instead of lifting their
books nearer their eyes, or who raise their right shoulder above their
left when writing at a desk which is too high. Round shoulders, small,
weak lungs, and, frequently, diseases of the spine are the consequences.
An erect posture in reading or writing conduces not alone to beauty of
form, but also to health of body. We shall learn hereafter that the action
of the muscles bears an important part in preserving the symmetry of the
spine. Muscular strength comes from bodily activity; hence, one of the
best preventives of spinal curvature is daily exercise in the open air.
5. _Sprains_ are produced when the ligaments which bind the bones of
a joint are strained, twisted, or torn from their attachments. They are
quite as serious as a broken bone, and require careful attention lest they
lead to a crippling for life. By premature use a sprained limb may be
permanently impaired. Hence, the joint should be kept quiet, even after
the immediate pain is gone.
6. _A Dislocation_ is the forcible displacement of a bone from its
socket. It is, generally, the result of a fall or a violent blow. The
tissues of the joint are often ruptured, while the contraction of the
muscles prevents the easy return of the bone to its place. A dislocation
should be reduced as soon as possible after the injury, before
inflammation supervenes.
PRACTICAL QUESTIONS.
1. Why does not a fall hurt a child as much as it does a grown person?
2. Should a young child ever be urged to stand or walk?
3. What is meant by "breaking one's neck"?
4. Should chairs or benches have straight backs?
5. Should a child's feet be allowed to dangle from a high seat?
6. Why can we tell whether a fowl is young by pressing on the point of the
breastbone?
7. What is the use of the marrow in the bones?
8. Why is the shoulder so often put out of joint?
9. How can you tie a knot in a bone?
10. Why are high pillows injurious?
11. Is a stooping posture a healthful position?
12. Should a boot have a heel piece?
13. Why should one always sit and walk erect?
14. Why does a young child creep rather than walk?
15. What is the natural direction of the big toe?
16. What is the difference between a sprain and a fracture? A dislocation?
17. Does the general health of the system affect the strength of the
bones?
18. Is living bone sensitive? _Ans_.--Scrape a bone, and its vessels
bleed; cut or bore a bone, and its granulations sprout up; break a bone,
and it will heal; cut a piece away, and more bone will readily be
produced; hurt it in any way, and it inflames; burn it, and it dies. Take
any proof of sensibility but the mere feeling of pain, and it will answer
to the proof.--BELL'S _Anatomy_. Animal sensibility would be
inconvenient; it is therefore not to be found except in diseased bone,
where it sometimes exhibits itself too acutely.--TODD'S _Cyclopedia of
Anatomy_.
19. Is the constitution of bone the same in animals as in man?
_Ans_.--The bones of quadrupeds do not differ much from those of man.
In general they are of a coarser texture, and in some, as in those of the
elephant's head, we find extensive air cells.--TODD'S _Anatomy_.
II.
THE MUSCLES.