UC-NI

SAN FRANCISCO

for its coming righ
intelligent teacher
recommend it.

" In a very sma!
whole History of t
office in this count
possible in a narra
thousands of even
historical periods-
pire, that of Charl'
tive. We can end'
From Prof. WM. P

u It is very hare
how to teach and \
is necessary, and r,
From R. M. LUSHJ

" This Manual i
effect a reform in t
chronological reca
From Pi

" Your Manual
and subjected to tl
It is tlie best corny

subject in the choice, "ancr^rr'arrgcmciu 01 mt! aetans, m me cieuinesg ana Minpiicuy of
the'language, in the omission of the endless and uninteresting minutiae with which many
text-books on this subject are cumbered, you have been highly successful. Unlike most
compends of history, the narrative is well connected and pleasing, thereby attracting
rather than repelling the student. Nor are the maps among the least valuable features of
the book. You have fully recognized the principle that the Study of History and Geog-
raphy should go hand in "irand It is extremely gratifying to find a book that

furnishes the pupil with the leading facts of history in so attractive a manner, and leaves
to the teacher so large an opportunity for oral instruction."

Published by Clark & Maynard, 5 Barclay St., New York,

ANDERSON'S SCHOOL HISTORIES.

Anderson's Pictorial School History of the United States.

By JOHN J. ANDERSON, A. M., Late Principal of Grammar School
No. 31, New York City; Author of a Grammar School and other
Histories of the United States, and of a Manual of General History.
Beautifully illustrated with about two hundred maps, portraits, vignettes,
etc. "With an appendix containing the Constitution of the United
States, with questions and explanations, and the Declaration of Inde-
pendence. 12mo. 400 pages.

The distinctive features of this work are : — 1st. A system of maps, with map questions
and references, combining the geography with the chronology, thus teaching 'byAhe eye
as well as the ear, and consequently making the impression upbii the memory more4ast-%'
ing. 2d. A second set of questions differing entirely from the first. The'se," by associat-
ing facts belonging to the same class or train of events, require answerp o£ a topical
character, and thus compel the student to review his lessons witbthoughtfiflness.

From the Hon. H. H. VAN DYCK, former Superintendent of Public. Instruot&m for' the

State of New York. r

"The books comprising Anderson's Series of School Histories have-^een in my pos-
session during the last six months. I have examined them with considerable care, and
find them works of decided merit. There is a directness, clearness, and conciseness in
the statements, and an admirable method connected with the chronological and geogra-
phical features of the narrative, that commend them to my judgment. To the instructor
who aims at thoroughness in the knowledge imparted to his pupils of our country's
history, these books arc certainly invaluable. I recommend them without reservation.'"

From-C. B. PARSONS, D. D., LL.D., Chairman of Coinmittee of Examination and Control

of Public Schools, Louisville, Ky.

"I have carefully examined the 'Pictorial History of the United States,' by John J.
Anderson, and unhesitatingly pronounce it the best of its kind that has fallen under my
observation. Its remarkable comprehensibility, so concisely given, " multum inparvo,
with its excellent arrangement of adaptation to the purposes of instruction, canuot fail
to recommend it to general use. I most cordially approve of its introduction into our
schools."

From Rev. J. M. ANDERSON, Principal of Ohio Female College, College Hill, Ohio.

"The book stands well the most careful scrutiny. I am particularly pleased with the
fairness of its statements as to the results of battles, etc. The history of our country is
rich enough in great deeds to warrant the historian in telling the whole truth, and
nothing but the truth, as to her reverses and misfortunes. Without truth, history is a
delusion and a snare. In point of method, clearness, and succinctness of narration,
also, I regard this book as incomparably the best manual of the kind that has appeared.
None but a practical and experienced teacher could have produced such a model class-
book. We shall lose no time in introducing it into this Institute."

From Miss JANE A. BARTHOLOMEW, the luell-knoivn teacher of History in the Connecticut

State Normal School.

" In respect to symmetry of plan, proportionate arrangement of matter, correctness,
clearness, and conciseness of statement, and in variety or explanatory information, it is
superior to any other text-book in United States history used here. The seals of the
States and miniature maps, are valuable additions to the book ; while the charts and
questions for review, condensing gradually, as they do, its whole contents, meet a want
which many teachers have neither the means nor ability to supply."

PUBLISHED BY

NEW YORK.

THK VISCERA IN POSITION.

TREATISE

ON

PHYSIOLOGY AND HYGIENE

FOR

EDUCATIONAL INSTITUTIONS AND GENERAL
READERS.

FULLY ILLUSTRATED.

JOSEPH C. HUTCHISON, M. D.,

President of the New York Pathological Society, Vice- President of the New York

Academy of Medicine, Surgeon to the Brooklyn City Hospital, late President

of the Medical Society of the State of New York, etc.

NEW YORK:

CLARK & MAYNARD, PUBLISHERS,

5 BARCLAY STREET.

1872.

4

<xy

Entered according to Act of Congress, in the year 1870,

By CLARK & MAYNARD.
In the Office ol the Librarian of Congress, at Washington,

EDUCATION

Stereotyped by LITTLK, KKNMK A Co..
846 and 647 Broadway.

TO MY WIFE,

'WHOSE SYMPATHY HAS, TOR MORE THAN TWENTY YEARS, LIGHTENED THB
CARES INCIDENT TO

AN ACTIVE PROFESSIONAL LIFE,

THIS HUMBLE VOLUME

IS AFFECTIONATELY INSCRIBED.

543488

PREFACE.

THIS work is designed to present the leading facts and principles
of human Physiology and Hygiene in clear and concise language,
so that pupils in schools and colleges, and readers not familiar with
the subjects, may readily comprehend them. Anatomy, or a de-
scription of the structure of an organ, is of course necessary to the
understanding of its Physiology, or its uses. Enough of the former
study has, therefore, been introduced, to enable the pupil to enter
intelligently upon the latter.

Familiar language, as far as practicable, has been employed,
rather than that of a technical character. With a view, however,
to supply what might seem to some a deficiency in this regard, a
Pronouncing Glossary has been added, which will enable the in-
quirer to understand the meaning of many scientific terms not
in common use.

In the preparation of the work the writer has carefully examined
all the best material at his command, and freely used it ; the special
object being to have it abreast of the present knowledge on the sub-
jects treated, as far as such is possible in a work so elementary as
this. The discussion of disputed points has been avoided, it being
manifestly inappropriate in a work of this kind.

Instruction in the rudiments of Physiology in schools does not
necessitate the general practice of dissections, or of experiments upon
animals. The most important subjects may be illustrated by draw-

4 PEEFACE.

ings, such as are contained in this work. Models, especially those
constructed by Auzoux of Paris, dried preparations of the human
body, and the organs of the lower animals, may also be used with
advantage.

The writer desires to acknowledge his indebtedness to R M
WYCKOFF, M.D., for valuable aid in the preparation of the manu-
script for the press; and to R. CRESSON STILES, M.D., a skilful
microscopist and physician, for the chapter " On the Use of the
Microscope in the Study of Physiology." Mr. AVON C. BURNHAM,
the well-known teacher of gymnastics, furnished the drawing of
the parlor gymnasium and the directions for its use.

Brooklyn, N. Y.< 1870.

CONTENTS.

CHAPTER I.

PAGE

THE FRAMEWORK OF THE BODY 15

The Bones — Their form and composition — The Properties of Bone — The
Skeleton — The Joints — The Spinal Column — The Growth of Bone —
The Repair of Bone.

CHAPTER II.
THE MUSCLES 26

The Muscles — Flexion and Extension — The Tendons — Contraction —
Physical Strength — Necessity for Exercise — Its Effects — Forms of
Exercise — Walking — Riding — Gymnastics — Open-air Exercise —
Sleep — Recreation.

CHAPTER III.
THE INTEGUMENT, OR SKIN 4

The Integument — Its Structure — The Nails and Hair — The Complexion
— The Sebaceous Glands — The Perspiratory Glands — Perspiration
and its uses — Importance of Bathing — Different kinds of Baths —
Manner of BatJiing — The Benefits of the Sun — Importance of
Warm Clothing — Poisonous Cosmetics.

CHAPTER IV.

THE CHEMISTRY OF FOOD 53

Tne Source of Food — Inorganic Substances — Water — Salt — Lime — Iron
— Organic Substances — Albumen, Fibrin, and Casein — The. Fats or
Oils — The Sugars^ Sfaich, and Gam — Stimulating Substances-
Necessity of a Regulated Diet.

CONTENTS.

CHAPTER V.

PAG15
FOOD AND DRINK 64

Necessity for Food — Waste and Repair — Hunger and Thirst — Amount
of Food — Renovation of the Body — Mixed Diet — Milk — Eggs — Meat
— Cooking — Vegetable Food — Bread — The Potato — Fruits — Purity
of Water— Action of Water upon Lead—Goffer, Tea, and Chocolate
— Effects of Alcohol.

CHAPTER VI.

DIGESTION 80

The Principal Processes of Nutrition — The General Plan of Digestion —
Mastication — The Teeth — Preservation of the Teeth — Insalivation
— The Stomach and the Gastric Juice — The Movements of the
Stomach — Gastric Digestion — The Intestines — The Bile and Pan-
creatic Juice — Intestinal Digestion — Absorption by means of Blood-
vessels and Lacteals — The Lymphatic or Absorbent System — The
Lymph — Conditions which affect Digestion — The Quality, Quan-
tity, and Temperature of the Food — The Influence of Exercise and
Sleep.

CHAPTER VII.
THE CIRCULATION 101

The Blood — Its Plasma and Corpuscles — Coagulation of the Blood — The
Uses of tJie Blood — Transfusion — Change of Color — The Organs of
the Circulation — The Heart, Arteries, and Veins — The Cavities
and Valves of the Heart — Its Vital Energy — Passage of the Blood
through the Heart — 1 he Frequency and Activity of its Movements —
The Pulse — The Spygmograph — TJie Capillary Blood-vessels — The
Bate of the Circulation — Assimilation — Injuries to the Blood-vessels.

CHAPTER VIII.
RESPIRATION 123

The Objects of Respiration — TJie Lungs — The Air- Passages— Vie Move-
ments of Respiration — Expiration and Inspiration — TJie Frequency
of Respiration — Capacity of the Lungs — The Air ice Breathe—
Changes in the Air from Respiration — Changes in the Blood — In-
terchange of Oases in the Lungs — Comparison between Arterial and

CONTENTS. 7

Venous Blood — Respiratory Labor — Impurities of the Air — Dust —
Carbonic Acid — Effects of Impure Air — Nature's Provision for
Purifiying the Air — Ventilation — Animal Heat.

CHAPTER IX.

PAGE

THE NERVOUS SYSTEM 148

Animal and Vegetative Functions — Sensation, Motion, and Volition —
The Structure of the Nervous System — The White and Gray Sub-
stances— The Brain — Its Convolutions — The Cerebellum — The Spi-
nal Cord and its System of Nerves — The Anterior and Posterior
Roots — TJie Sympathetic System of Nerves — The Properties of Nerv-
ous Tissue — Excitability of Nervous Tissues — The Functions of the
Spinal Nerves and Cord— The Direction of the Fibres of the Cord —
Reflex Activity and its Uses — The Functions of the Medulla Oblon-
gata and the Cranial Ganglia — The Reflex Action of the Brain.

CHAPTER X.

THE SPECIAL SENSES 177

The Production of Sensations — Variety of Sensations — General Sensi-
bility— Pain and its Function — Special Sensation, Touch, Taste,
Smell, Sight, and Hearing — The Hand, the Organ of Touch — The
Sense of Touch — Delicacy of Touch — Sensation of Temperature and
Weight — The Tongue t/ie Organ of Taste — The Nerves of Taste —
The Sense of Taste, and its Relations with the other Senses — The
Influence of Education on the Taste — The Nasal Cavities, or the
Organs of Smell — The Olfactory Nerve — The Uses of the Sense of
Smell— The Sense of Sight— Light— The Optic Nerve— The
Eyeball and its Coverings — The Function of the Iris — The
Sclerotic, Choroid, and Retina — The Tears and their Func-
tion— The Movements of the Eyeball — The Function of Ac-
commodation— The Sense of Hearing and Sound— The Ear, or
the organ of Hearing — The External, Middle, and Internal Ear.

CHAPTER XI.

THE VOICE 227

Voice and Speech — Ihe Larynx, or the Organ of the Voice — The Vocal
Cords— The Laryngoscope— The Production of the Voice— The Use
of the Tongue— The different Varieties of Voice— The Change of
Voice — Its Compass — Purity of Tone — Ventnloquy.

b CONTENTS.

*

CHAPTER XH.

FAOB
THE USE OF THE MICROSCOPE IX THE STUDY OF

PHYSIOLOGY 236

The Law of Tissues — Necessity of the Microscope — Different kinds of
Microscopes — Additional Apparatus — Preliminary Studies — The
Study of Human Tissues — Tissues of t?ie Inferior Animal* — Incen-
tives to Study.

APPENDIX.

POISONS AND THEIR ANTIDOTES , . , . - . ^, 247

GLOSSARY ^52

LIST OF ILLUSTRATIONS

FRONTISPIECE,
VISCERA IN POSITION,

1. Section of bone, 17

2. Structure of bone, magnified, .... 17

3. The skeleton, . , 18

4. Cells of cartilage, 20

5. Elbow-joint, . , 21

6. Spinal column, 22

7. The muscles, ........ 24

8. Muscular tissue, magnified, . •£ • • • 25

9. Biceps muscle of the arm, .... .26

10. View of knee-joint, ....... 27

n. Appliance for strengthening the muscles, . . -35

12. Appliance for strengthening the muscles, 35

13. Parlor gymnasium, 36

14. Root and transverse section of hair, magnified, . . 43

15. Granules of potato starch, . . . . . .61

1 6. Section of the trunk, 81

17. Section of a tooth, . . . . . . .82

1 8. Section of the jaws, 82

19. Section of the jaws — right side, 84

20. Structure of a salivary gland, ..... 87

21. Head of a horse, showing salivary gland, etc. . . 87

22. Section of chest and abdomen, . . . . 90

23. Organs of digestion, . . . . . . 91

24. The lacteals, 97

25. Blood corpuscles, . . . . . . • .102

26. Blood corpuscles of man and lower animals, . . - 103

27. Circulation of the blood, . . . . . . 108

10 LIST OF ILLUSTRATIONS.

FIG. PAGE

28. Heart and large vessels, 109

29. Section of the heart, 1 10

30. Form of the pulse, 116

31. Valves of the veins, . . . . . . . 117

32. Web of frog's foot, magnified, 119

33. Circulation in a frog's foot, 119

34. Organs of the chest, 124

35. Larynx, trachea, and bronchial tubes, . . . .125

36. Diagram of the structure of the air-cells, . . . 125

37. Section of the lungs, . . . . . . .126

38. Section of mouth and throat, 127

39. Ciliated cells, 128

40. Cerebro-spinal system, . . . . . . 151

41. Upper surface of the cerebrum, 153

42. Vertical section of the brain, 154

43. Base of the brain, 155

44. Brain and spinal cord, . . . . . . 156

45. Sense of touch, 185

46. Section of nasal cavity, 193

47. Front view of th^^ye, ....... 200

48. Vertical section of eye, ...... 202

49. Diagram for blind point of eye, 207

50. Retinal image, . . . . . . 210

51. Different shapes of the globe of the eye, . . .212

52. Function of accommodation, 214

53. Diagram of the ear, 218

54. Section of the ear, 221

55. Section of larynx and trachea, . . 229

56. View of vocal cords by the laryngoscope, . . . 232

57. Different positions of vocal cords, .232

58. Simple microscope, 238

59. Compound microscope, 239

60. Household microscope, ...... 240

61. Popular microscope., 241

INTRODUCTION.

THE Human Body is the abode of an immortal spirit,
and is the most complete and perfect specimen of the
Creator's handiwork. To examine its structure, to ascer-
tain the uses and modes of action of its various parts,
how to protect it from injury, and maintain it in a
healthy condition, is the design of this work.

The departments of knowledge which are concerned
in these investigations, are the science of Human Physi-
ology and the art of Hygiene.

PHYSIOLOGY treats of the vital actions and uses of the
various parts of living bodies, whether vegetable or ani-
mal. Every living thing, therefore, has a Physiology.
We have a Vegetable Physiology, which relates to plants ;
and an Animal Physiology, relating to the animal king-
dom. The latter is also divided into Comparative Physiol-
ogy, which treats of the inferior races of animals, and
Human Physiology, which teaches the uses of the various
parts of the human body.

HYGIENE, or the art of preserving health, is- the practi-
cal use of Physiology. It teaches us how to cultivate our
bodily and mental powers, so as to increase our strength
and to fit us for a higher enjoyment of life. It also shows
us how to prevent some of the accidents which may befall
the body, and to avoid disease. It is proper that we should

13 INTRODUCTION.

understand the construction and powers of our bodies ; but
it is our duty, as rational beings, to know the laws by which
health and strength may be maintained and disease warded
off.

There are various means by which we gain important
information respecting the Physiology of man. Plants
aid us in understanding the minute structure of the hu-
man body, its circulation, and absorption. From inferior
animals we learn much in respect to the workings of the
different organs, as we call those parts of the system which
have a particular duty to perform. In one of them, as in
the foot of the frog, we can study the circulation of the
blood; in another, we can study the action of the brain.

By vivisection, or the laying bare of some organ of a
living animal, we are able to investigate certain vital
processes which are too deeply hidden in the human body
to be studied directly. This is not necessarily a cruel
procedure, as we can, by the use of anaesthetics, so blunt
the sensibility of the animal under operation, that he
need not suffer while the experiment is being performed.
There are other means by which we gather our informa-
tion. There are occasionally men, who, from some acci-
dent, present certain parts, naturally out of view, in
exposed positions. In these cases, our knowledge is of
much greater value than when obtained from creatures
lower in the scale of being than man.

We are greatly aided, also, by the use of various instru-
ments of modern invention. Chief among these is the
microscope, which is, as we shall learn hereafter, an ar-
rangement and combination of lenses in such a way as
greatly to magnify the objects we wish to examine.

INTRODUCTION.

We have much to say of Life, or vital activity, in the
course of our study of Physiology ; but the most that we
know of it is seen in its results. What Life is, or where its
precise position is, we are not able to determine. We dis-
cover one thing, however, that all the parts of the body
are united together with wonderful sympathy, so that one
part cannot be injured and other parts not suffer damage.
It is further evident that all organs are not equally im-
portant in carrying on the work of Life; for some may
temporarily suspend their action, without serious results
to the system, while others must never cease from acting.
Yet there is nothing superfluous or without aim in our
frames, and no part or organ can suffer harm without
actual loss to the general bodily health. On this point
Science and Holy Writ strictly agree.

PHYSIOLOG-Y,

AND

HYGIENE.

CHAPTER I.
THE FRAMEWORK OF THE BODY.

Tlie Bones — Their Form and Composition — The Properties of Bone —
Tlie Skeleton— Tlie Joints— The Spinal Column— The Growth of
Bone — The Repair of Bone.

1. The Bones. — The framework which sustains the
human body is composed of the Bones. The superstructure
consists of the various organs on which the processes of
life depend. These organs are soft and delicately formed,
and, if unprotected, would, in most cases, rapidly be de-
stroyed when subjected to violence, however slight. The
bones, having great strength and power of resistance, afford
the protection required.

2. The more delicate the organ, the more completely does
Nature shield it. For example : the brain, which is soft in
structure, is enclosed on all sides by a complete box of bone ;
the eye, though it must be near the surface of the body
to command an extensive view, is sheltered from injury
within a deep recess of bone; the lungs, requiring freedom
of motion as well as protection, are surrounded by a large
case of bone and muscle. The bones serve other useful
purposes. They give permanence of form to the body, by

1 . The framework of the body ? The superstructure ? Softness and delicacy
of the organs ? How protected ?

2. The more delicate the organ ? Example in relation to the brain ? The eye ?
The lungs ? The services performed by the bones ?

1C - fll-E FRAMEWORK OF THE BODY.

holding rhe softer parts in their proper places. They
assist in movement, by affording points of attachment to
those organs which have power of motion — the muscles.

3. The Form and Composition of the Bones.—
Their shape and size vary greatly in different parts of the
body, but generally they are arranged in pairs, one bone for
each side of the body. They are composed of both mineral
and animal substances, united in the proportion of two
parts of the former to one of the latter ; and we may sep-
arate each of these substances from the other for examina-
tion. First, if we expose a bone to the action of fire,
the animal substance is driven off, or " burned out." We
now find that, though the shape of the bone is perfectly
retained, what is left is no longer tough, and does not sus-
tain weight as before. Again, we may remove the mineral
portion, which is a form of lime, by placing a bone into a
dilute acid. The lime will be dissolved out, and the shape
of the bone remain as before; but now its firmness has
disappeared, and it may be bent without breaking.

4. If, for any reason, either of these ingredients is dis-
proportionate in the bone during life, the body is in
danger. The lime is useful in giving rigidity of form,
while the animal substance insures toughness and elas-
ticity. By their union, we are able to withstand greater
shocks and heavier falls than would be possible with
either alone. In youth, the period of greatest activity,
the animal constituent is in excess: a bone then does
not break so readily, but, when broken, unites with great
rapidity and strength. On the other hand, the bones of
old persons are more easily broken, and in some cases fail
to unite. The mineral matter being then in excess, indi-
cates that the period of active exertion is drawing to a
close.

3. Their shape and size * Of what composed? Possibility of being separated ?
Effect of fire ? Of dilute acid ?

4. Effect of deficiency of ingredient ? Usefulness of the lime ? Of the animal
substance? Effect of their union ? Condition, in youth? Old age?

THE FRAMEWORK OF THE BODY.

1?

5. The Structure of the Bones. — If we examine one
of the long bones, which has been sawn through length-
wise, we observe that it is admirably fashioned for affording

A. Longitudinal B. Transverse section of bone.

FIG. 1.— SECTION op BONE.

lightness as well as strength (Fig. 1). Its exterior is hard
and resisting, but it is porous at the broad extremities,
while through the central portion
there is a cavity or canal which con-
tains an oily substance, called marrow.
Let us now take a thin section of
bone, and examine it under the mi-
croscope ; we discover that it is pierced
by numerous fine tubes (Fig. 2),
about which layers of bone-substance
are arranged. Accordingly, though a
bone be as hard as stone externally, it
is by no means as heavy as stone, by
reason of its light interior texture.
Another element of power is found in
the curved outline of the bones. The pre 2

curved line is said to be " the line of structure of bone en-
beauty," as it certainly is the line of lar£ed-
strength, and is uniformly employed
in the bones whose position exposes them to accident.

5. In what respect admirably fashioned ? Its formation? Microscopic exam
Ination ? The inference ? " Line of beauty ?"

FIG. 3.— THE SKELETON

THE FRAMEWORK OF THE BODY. 19

6. The Skeleton. — The number of bones in the human
body exceeds two hundred. When these are joined together
in the proper places, they form what is termed the Skeleton
(Fig. 3). It embraces three important cavities. The first,
surmounting the frame, is a box of bone, called the skull;
below this, is a bony case, or " chest ;" anl lower down is
a bony basin, called the pelvis. The two latter compose
the trunk. The trunk and skull are maintained in their
proper relations by the " spinal column/' Branching from
the trunk are two sets of limbs: the arms, which are
attached to the chest by means of the " collar-bone" and
" shoulder-blade ;" and the legs, directly joined to the lower
part of the trunk.

7. The cavities of which we have spoken, are designed
for the lodgment* and protection of the more delicate and
perishable parts of the system. Thus, the skull, together
with the bones of the face, shelters the brain and the
organs of four senses — sight, hearing, smell, and taste.
The chest contains the heart, lungs, and great blood-ves-
sels, while the lower part of the trunk sustains the liver,
stomach, and other organs

8. The Joints. — The point of union of two or more
bones forms a joint or articulation, the connection being
made in various ways according to the kind and amount
of motion desired. The movable joints are compacted
together by certain strong fibrous bands, called ligaments.
These ligaments are of a shining, silvery whiteness, and
very unyielding; so much so, that when sudden violence
is brought to bear in the vicinity of a joint, the bone to
which a ligament is attached may be broken, while the
ligament itself remains uninjured. When this connect-
ing material of the joints is strained or lacerated by an ac-

6. Number of bones? Skeleton? The skull ? Chest? The trunk ? The trunk
and skull, how maintained ? What of the arms ? Legs ?

7. Design of the cavities ? Give the examples.

8. Joint or articulation ? Movable joints, how compacted? The ligaments of
the movable joints ? What is a sprain ? Consequence of a serious sprain ?

20 THE FRAMEWORK OF THE BODY.

cident, a "sprain" is the consequence. An injury of this
sort may be, and frequently is, quite as serious as the
breaking of a bone.

9. The ligament, then, secures firmness to the joint;
it must also have flexibility and smoothness of motion.
This is accomplished by a beautiful mechanism the perfec-
tion of which is only feebly imitated by the most ingenious
contrivance of man. The ends of the bones are covered
by a thin layer of cartilage, which being smooth and elas-
tic, renders all the movements of the joint very easy. In
addition to this, there is an arrangement introduced for
"lubricating" the joint, by means of a delicate sac con-
taining fluid. This fluid is constantly supplied in small
quantities, but only so fast as it is used up in exercise.
In appearance, it is not unlike the white of an egg, and
hence its name synovia, or egg-like.

10. Thus, we observe, that two
very different substances enter into
the composition of a joint. The
ligament, very unyielding, affords
strength, while the cartilage, elastic
and moist, gives ease and smooth-
ness of motion. The amount of
motion provided for varies greatly
in different joints. In some there is
none at all, as in the skull, where
jg» one bone is dove-tailed into another
by what are termed sutures. Others
have a hinge-like motion, such as

Fro. 4.-CELLS op CARTILAGE. faOSQ Qf ftie elbow, wrist, ankle,

and knee; the most complete of these being the elbow-
joint (Fig. 5). Belonging to another class, the ball-and-

9. Office of the ligament ? What must it have ? How accomplished ? Describe

1 1 of "what do we observe as resards the composition of a joint ? The lament
and cart ilajre? What varies? Example of the skull? Other examples ?
ball-and-socket joint?

THE FRAMEWORK OF THE BODY.

socket joint, is that at the shoulder, possessing a freedom
of motion greater than any other in the body.

Fio. 5.— ELBOW JOINT. A, Bone of the arm ; B, C, Bones of the fore-arm.

11. The Spinal Column. — The spjnal column is often
spoken of as the " back-bone," as if it were a single bone,
while, in reality, it is composed of a chain of twenty-six
small bones, called vertebra. The spinal column is a
wonderful piece of mechanism. It not only connects the
important cavities of the body, as has already been shown,
but, also, itself forms a canal, which contains the spinal
cord. The joints of the vertebrae are remarkable for the
thick layers of cartilage which separate the adjacent sur-
faces of bone. The amount of motion between any two
of these bones is not great; but these little movements,
taken together, admit of very considerable flexibility, in
several directions, without endangering the supporting
power of the column.

11. What is the spinal column ? What docs it connect and form ? Joints of
the vertebrae ? Amount of motion ? Result ?

22 THE FRAMEWORK OF THE BODY.

12. The abundant supply of intervertebral cartilage has
another important use, namely, it adds greatly to the
elasticity of the frame. It is due, in part,
to this elastic material, and in part to the
frequent curves of the spine, that the brain
and other delicate organs are protected from
the shock of sudden falls or jars. During
the day, the constant pressure upon these
joints, while the body is erect, diminishes
the thickness of the cartilages; so that a
person is not so tall in the evening as in
the morning. The effects of this compres-
sion pass away when the body reclines in a
horizontal position.

13. The Growth of Bone.— Bone, like
all the other tissues of the body, is con-
stantly undergoing change, old material
being withdrawn, and new particles taking
their place. This has been shown conclu-
sively by experiments. If an animal be fed
with madder — a red coloring matter — for a
day or two, the bones soon become tinged ;
then, if the madder be discontinued for a
few days, the original color returns. If, how-
ever, this material be alternately given and
withheld, at short intervals, the bone will
be marked by a succession of red and white
rings. In very young animals, all the bones
become colored in a single day; in older
FIG. 6.— THE ones, a longer time is required. The process
of waste and repair, therefore, is constantly
taking place in this hard substance, and with astonishing
rapidity.

1 2. Elasticity of the frame ? Protection of the brain from shocks Tallness
of persons ? Effects of reclining ?

13. Change in bone? Example— animal and madder. Rapidity of change in
color? Waste and repair?

•

THE FRAMEWORK OF TIJE BODY. 23

14. The Repair of Bone. — Nature's provision for
uniting broken bones is very complete. At first, blood is
poured out around the ends of the bone, as a result of
the injury. This is gradually absorbed, and gives place
to a watery fluid, which, thickening from day to day, ac-
quires, at the end of two weeks, the consistency of jelly.
This begins to harden, by a deposit of new bone-substance,
until, at the expiration of five or six weeks, the broken
bone may be said to be united. It is, however, still fragile,
and must be used carefully a few weeks longer. The
process of hardening continues, and months must pass
before the union can be said to be complete.

QUESTIONS FOR TOPICAL REVIEW.

PAGE

1. What useful purposes do the bones serve ? 15, 16

2. State what you can of the composition of the bones 16

3. Of the usefulness of lime in the bones 16

4. Of the usefulness of animal substance in the bones 16

5. State what you can of the structure of the bones 17

6. Of the strength belonging to the bones '. 15. 16, 17

7. What is meant by the human skeleton ? 19

8. Give a description of its construction 19

9. What is meant by a joint in the human frame ? 19

10. State what you can of the movable joints 19, 20

11. What office is performed by the ligaments of the joints ? 19, 20

12. What by the cartilage at the joints ? 20

13. What movable joints are there ? 20, 21

14. Describe the construction of the spinal column 21

15. What properties and powers does the spinal column possess ? 21, 22

16. When is a person taller than at other times ? . . 22

17. Give the reason for this 22

18. What can you state of the growth of bone ? 22

f 19. Describe the process by which a broken bone is repaired 23

M ' Jr' w ft si

y^x^v -fc-t^

'*

:

THE MUSCLES.

FIG. 7.— TUB MUSCLES.

THE MUSCLES.

CHAPTER II.

THE MUSCLES.

The Muscles— Flexion and Extension— The Tendons— Contraction-
Physical Strength— Necessity for Exercise— Its Effects— Forms of
Exercise — Walking — Riding — Gymnastics — Open-air Exercise —
Sleep — Recreation.

1. The Muscles. — The great mass of the body exter-
nal to the skeleton, is composed of the flesh, or Muscles,
which largely determines its outline and weight. The
muscles are the organs of motion. Their number is
about four hundred, and to each of them is assigned a
separate and distinct office. They have all been studied,
one by one, and a name given to each, by the anatomist.
Each is attached to bones which it is designed to move.
A few are circular in form, and enclose cavities, the size
of which they diminish by contraction.

2. If we examine a piece of flesh, we observe that it is
soft, and of a deep red color. Its structure appears to be

composed of layers
and bundles of small
fibres. Let us fur-
ther examine these
fibres under the mi-
croscope. We now
discover that they
are, in turn, made up
of still finer fibres,
or fibrillce : these are

FIG. 8— MUSCULAR TISSUE.
a 6, Striped muecular fibres: c, The game more Seen in rig. 8. ihe

fibres are beautifully

1 . What are the muscles ? Their number ? The design of most of them ? Of
a few?

2. The structure of flesh? Its color, etc.? The composition of the fibres?
How marked?-

THE MUSCLES.

-B

marked by parallel wavy lines, about ten thousand to an
inch, which give the fibre its name of the striped muscular
fibre. All of the voluntary muscles present this appearance.
3. Flexion and Extension.— The muscles are, for
the most part, so arranged in pairs, or corresponding
sets, that when motion is produced in one direction by
one set, there is, opposite to it, another
muscle, or group of muscles, which
brings the limb back to its place. When
they act alternately, a to-and-fro move-
ment results. When a joint is bent, the
motion is called flexion; and when it is
made straight again, it is called exten-
sion. When both sets act equally, and
at the same moment, no motion is pro-
duced, but the body or limb is main-
tained in a fixed position: this occurs
when we stand erect. The muscles
which produce extension are more pow-
erful than those opposite to them.

4. The muscles are also distinguished,
on the other hand, as the voluntary
and involuntary muscles, according as
they are, or are not, under the control
of the will. The heart is an example of
the involuntary variety. We cannot
change its action in the least by an
effort of the will. When we sleep, and
the will ceases to act, the heart contin-
ues to beat without cessation. The voluntary muscles,
on the other hand, are such as are used only when we wisn
or will to use them — as the muscles of the hand or arm
(Pig. 9).

FIG. 9. — A, Biceps mus-
cle of the arm: B, C,
Its tendons.

3. Arrangement of the muscles? Their action ? Flexion and extension? Ac-
tion of the muscles when we stand erect ?

4. Kinds of muscles? The voluntary? Involuntary? The heart? Give the
example. The hand ? Arm ?

THE MUSCLES.

5. The Tendons. — Tendons, or sinews, are the ex-
tremities of muscles, and are compactly fastened upon
bone. They are very strong, and of a silvery whiteness.
They may be felt just beneath the skin, in certain parts of
the body, when the muscles are being used, as at the bend
of the elbow or knee. The largest tendon of the body is
that which is inserted into the heel, called the tendon of
Achilles, after the hero of the Grecian poet, the fable relat-
ing that it was at this point that he received his death-
wound, no other part of his body being vulnerable. The
muscles "which extend into the leg unite to form a single

FIG. 10. -VIEW OF KNEE-JOINT. A. Thigh bone: B, Knee-pan : C, D, Leg bones.

and very powerful tendon, and enclose a small bone called
the knee-pan, which, acting like a pulley, greatly increases
their power, and at the same time protects the front of the
knee-joint (Fig. 10).

6. Muscular Contraction. — The muscles, when acted
upon by the appropriate stimulus, contract, or so change

5. What are the tendons or sinews? Their strength? Color? Location?
Tendon of Achilles ? The fable ? Muscles of the leg ?

6. Contraction of the muscles ? Bending of the arm or finger ? Other agencies ?
Automatic movements ? In cold-blooded animals ?

28 THE MUSCLES.

their shape, that their extremities are brought nearer to-
gether. The bending of the arm, or of a finger, is effected
in this manner, by the will; but the will is not the only
means of producing this effect. Electricity, a sharp blow
over a muscle, and other stimuli, also cause it. Contrac-
tion does not always cease with life. In man ,:.after death
from cholera, automatic movements of hands and feet
have been observed, lasting not less than an hour. In
certain cold-blooded animals, as the turtle, contraction
has been known to take place for several days after the
head has been cut off.

7. The property which, in muscle, enables these move-
ments to take place is called contractility. If we grasp a
muscle while in exercise (for example, the large muscle in
the front of the arm), we notice the alternate swelling and
decrease of the muscle, as we move the forearm to and fro.
It was at one time supposed that the muscle actually in-
creased in volume during contraction. This, however, is
not the case ; for the muscle, while gaining in thickness,
loses in length in the same proportion; and thus, the
volume remains the same in action and at rest.

8. Contraction is not the permanent, or normal, state
of a muscle. It cannot long remain contracted, but after
a shorter or longer time, it wearies and is obliged to relax.
After a short rest, it can then again contract. It is for
this reason that the heart can beat all through life, night
and day, by having, as we shall hereafter see, a brief inter-
val of rest between successive pulsations. For the same
reason, it is more fatiguing to stand for any great length of
time in one position, than to be walking the same period.

9. Relative Strength of Animals.— The amount
of muscular power which different animals can exert, has

7. Contractility? Give the illustration. What was supposed? What is the
case?

8. What further in relation to contraction ? Weariness of a muscle ? Beating
of the heart ? Standing and walking ?

9. Muscular power of animals ? How tested ? Man's power ? Worse's ? The
comparison ?

THE MUSCLES. 29

been tested by experiment. By determining the number
of pounds which an animal can drag upon a level surface,
and afterward comparing that with its own weight, we can
judge of its muscular force. It is found that man is able
to drag a little less than his own weight. A draught-horse
can exert a force equal to about two-thirds of his weight.
The horse, tnferefore, though vastly heavier than man, is
relatively not so powerful.

10. Insects are remarkable for their power of carrying
objects larger and heavier than themselves. Many of
them can drag ten, and even twenty times their weight.
Some of the beetles have been known to move bodies more
than forty times their own weight. So far, therefore, from
it being a fact that animals have strength in proportion
to their weight and bulk, the reverse of that statement
seems to be the law.

11. Physical Strength. — The difference in strength,
as seen in different individuals, is not due to any original
difference in their muscles. Nature gives essentially the
same kind and amount of muscles to each person, and the
power of one, or the weakness of another, arises, in great
part, from the manner in which these organs are used or
disused.

12. Many authors complain of the physical degeneracy
of men at the present day, as compared with past genera-
tions. There is room for doubt as to the correctness of
this statement. Certain experiments have recently been
made with the metallic armor worn seven hundred years
ago, by which it is found that any man, of ordinary height
and muscular development, can carry the armor and wield
the weapons of an age supposed to be greatly our superipr
in strength. When we consider that in those days, only
very strong men could endure the hardships of soldier-life,

1 0. Power of insects ? Beetles ? Give the conclusion.

11. Difference in strength of individuals ? How caused ?

12. ComplailUMn relation to degeneracy? How true? How determined by
armor ? The fair supposition ?

30 THE MUSCLES.

it is fair to suppose that our age has not so greatly degen-
erated in respect to physical strength.

13. Importance of Exercise. — Action is the law of
the living body. Every organ demands use to preserve
it in full vigor, and to obtain from it its best services.
The value of that training of the mind, which we call
education, is everywhere recognized. The child is early
put to school, and for many years continues to study, in
order that his brain, which is the great centre of mental
power, may act healthfully and with force. It is impor-
tant that the body, also, should receive its education by
exercise. This is especially true of persons belonging to
certain classes of society, whose occupation confines them
within doors, and requires chiefly brain-work.

14. Persons who are engaged in manual labor in the
open air obtain all the exercise necessary for bodily health
in their regular business: their need is more likely to be a
discipline or exercise of the mind. A perfect business of
life, therefore, would be one which would combine both
physical and mental labor in their proper proportions.
If such a business were possible for all the human race, life
would thereby be vastly prolonged. Such is, in fact, to a
large extent, the occupation pertaining to one period of
life — childhood. A part of the time is spent by the child
in improving his mind by study, and another part of the
time he has physical exercise in his games and sports.

15. The Effects of Exercise. — Exercise consists in
a well-regulated use of the voluntary muscular system.
The effects, however, are not limited to the" parts used.
Other organs, which are not under the control of the
will, are indirectly influenced by it. For instance, the
heart l*ats more rapidly, the skin acts more freely, and

13. Action? Use of organs? Training of the mind? The child's brain?
Education of the body ? •

1 4. Work in the open air ? A perfect business ? The consequence of universal
perfect business ? Occupation of children ?

1 5. In what does exercise consist ? Effects of it ?

THE MUSCLES. 31

becomes hotter, as well as the parts beneath it, and the ap-
petite and power of digestion are increased. An increased
exhalation from the lungs and skin purifies the current of
the circulation, and the body as a whole thrives under its
influence.

16. The immediate effect of exercise, however, is upon
the muscles themselves; for by use they become firm and
large, and increase in power. If we examine a muscle thus
improved by exercise, we find that its fibres have become
larger and more closely blended together, that its color is
of a darker red, and that the supply of blood-vessels has
increased. Without exercise the muscle appears thin,
flabby, and pale. On the- other hand, excessive exercise,
without sufficient relaxation, produces in the muscle a
condition not very different from that which follows dis-
use. The muscle is worn out faster than nature builds it
up, and it becomes flabby, pale, and weak.

17. Violent exercise is not beneficial; and spasmodic
efforts to increase the muscular strength are not calculated
to secure such a result. Strength is the result of a gradual
growth, and is most surely acquired if the exercise be
carried to a point short of fatigue, and after an adequate
interval of rest. To gain the most beneficial results, the
exercise should be at regular hours, and during a regular
period. The activity of the exercise, and the time de-
voted to it must vary, of course, with the strength of the
individual, and should be carefully measured by it.

18. Different Modes of Exercise. — There are very
few who have not the power to walk. There is required
for it no expensive apparatus, nor does it demand a period
of preliminary training. Walking may be called the uni-
versal exercise. "With certain foreign nations, the English

16. General effect upon the muscles? Special effect? Effects of inaction?
Of excessive exercise ?

17. Of violent and spasmodic efforts? Strength, how attained? Give the
particulars.

1 8 . What may walking be called ? What further is said of walking ?

32 THE MUSCLES.

especially, it is a very popular exercise, and is practised
habitually by almost every class of society ; by the wealthy
as well as by those who have no carriages; by women as
well as by men.

19. Running, leaping, and certain other more rapid and
Violent movements, are the forms of exercise that are
most enjoyed in childhood. For the child, they are not
too severe, but they may be so prolonged as to become
injurious. Instances have been recorded where sudden
death has resulted after violent playing, from overtaxing
the heart: for example, we have the case of a young girl
who, while skipping the rope, and endeavoring to excel
her playmates by jumping the greatest number of times,
fell dead from rupture of the heart.

20. Carriage-riding, as a means of passive exercise, is par-
ticularly well suited to invalids, and persons advanced in
life. Horseback exercise brings into use a greater number
of muscles than any other one exercise, and with it there
is an exhilaration of feeling which refreshes the mind at the
same time. It is one of the manliest of exercises, but not
less suitable for women than for men. To be skilful in
riding, it is best to begin its practice in youth ; but there
are very few kinds of exercise of which the same is not
equally true.

21. For those who live near streams or bodies of water,
there are the delightful recreations of boating, swimming,
and skating. Certain of these exercises have a practical
importance aside from and above their use in increasing
the physical vigor. This is especially true of boating and
swimming, since they are often the means of saving life.
Practice in these exercises also teaches self-reliance,
courage, and presence of mind. Persons who have become
proficient in these vigorous exercises are generally the ones.

1 9. What is paid of running, and other like movements ? What, as related to
childhood ? What instance:* are a I hided to ? Example ?

20. Carriage-riding? Horseback-riding?

21. Boating, swimming, and skating ?

THE MUSCLES. 33

who, in times of danger, are the quickest to act and the
most certain to do so with judgment.

22. Physical Culture.— That form of exercise which
interests and excites the mind, will yield the best results ;
but to some persons no kind of exertion whatever is, at
first, agreeable. They should, nevertheless, make a trial
of some exercise, in the expectation that, as they be-
come proficient in it, it will become more pleasant. In
exercise, as many sets of muscles should be employed
as possible, open-air exercise being the best. Parlor
gymnastics, and the discipline of the gymnasium are
desirable, but they should not be the sole reliance for
physical culture. No in-door exercise, however excellent
in itself, can fill the place of hearty and vigorous activity
in the open air.

23. Gymnastic Exercises for Schools and Col-
leges.— In the system of education among the ancients,
physical culture predominated. In ancient Greece, physi-
cal exercises in- schools were prescribed and regulated by
law, and hence these schools were called gymnasia. At
the present time, on the contrary, this culture is almost
wholly unknown, as a part of the course of education, in
our schools and colleges. In a few of our institutions of
learning, however, physical exercises have been intro-
duced, with manifest advantage to the students, and they
form a part of the regular curriculum of exercises, — as
much so as the recitations in geography, grammar, or
Greek. The good effect of the experiments, as shown in
improved scholarship as well as increased bodily v^gor, in
the institutions where the plan has been tried, will, it is
hoped, lead to its universal adoption. We should then
hear less frequently of parents being obliged to withdraw
their children from school, because they become exhausted

22. What kind uf exercise yields the best results ? What advice is given ?

23. Physical culture among the ancients ? In Greece ? In schools and college?
at the present time ? Result to the body and mind ?

2*

34 THE MUSCLES.

or, perchance, have lost their health from intense and pro-
tracted mental application.

24. Were gymnastics more common in our educational
institutions we should not so often witness the sad spectacle
of young men and women leaving our colleges and semi-
naries, with finished educations it may be, but with consti-
tutions so impaired, that the life which should be devoted
to the accomplishment of noble purposes must be spent in
search of health. Spinal curvatures, which, according to
the experience of physicians, are now extremely frequent,
especially among ladies, would give place to the steady
gait and erect carriage which God designed his human
creatures should maintain.

25. All the exercises necessary for the proper develop-
ment of the body may be obtained from the use of a few
simple contrivances that every one can have at home, at
little cost — less by far than is spent for useless toys. Many
of these may be made available in the parlor or chamber,
though all exercises are far more useful in the open air. A
small portion of the day thus spent will afford agreeable
recreation as well as useful exercise. The Indian club, the
wand, the ring, and the dumb-bells answer ordinary pur-
poses very well. Illustrations are here introduced of a few
simple contrivances that may be useful for general exer-
cises, and are specially suitable for persons with weak
spines , or with spines that are the subject of lateral curva-
ture.

26. One of the simplest appliances for strengthening
the muscles of the spine, designed chiefly to exercise the
muscles on either side of the spine, consists of two wooden
handles attached to india-rubber cords, one of which is
attached to a hook made fast in the ceiling, or in the top
of the door-case ; and the other to another hook fastened
in the wall, door-post, or window-casing, about the height

24. The result of gymnastics in our colleges and other institutions of learning?

THE MUSCLES.

of the shoulder. When traction is made with the left hand.,
it exercises the muscles on the left side of the spine, while

FIG. 11.

those on the opposite side are left almost at rest, owing to
the oblique direction given to the shoulders when the right

PIG. 12.

hand grasps the horizontal cord. (This appliance will be
understood by referring to Fig. 13.)

36

THE MUSCLES.

27. Fig. 11 shows an appliance consisting of two strong
elastic cords, with handles, secured to a hook in the floor,
so arranged that the patient has to stoop forward to reach
them. On raising the body the spinal muscles are power-
fully exercised. Fig. 12 shows other modes of using the
elastic cords for strengthening the spine and chest.

FIG. 13.

28. These various appliances have been combined so as
to form a system of gymnastics suitable for parlor use;
other appliances have been added by which the muscles of

THE MUSCLES. 37

the legs may be called into action as well as those of the
spine and upper part of the body (Fig. 13). Combinations
of cords suitable for particular cases may also be made, and
by using one or several cords on the same hook, their power
may be adapted to the strength of the most robust as well
as to that of the invalid, or of the most delicate child.
The entire apparatus is quite simple in its construction
and inexpensive, requiring but little space, and at the
same time affording a great variety of exercises.

EXERCISES THAT MAY BE PRACTISED o*r THIS APPA-
RATUS.

EXERCISE I. (Fig. 13). — Stand erect under the cords and place the
heels together. Grasp the handles firmly, keeping the knees and
elbows stiff, and pull downward and forward until the fingers nearly
touch the toes. Return slowly to the erect position. Repeat.

EXERCISE II. (Fig. 13). — Stand erect, and having grasped the
handles overhead firmly, separate them and bring them down
slowly until they touch the sides : then return them slowly to the
original position. Repeat.

EXERCISE III. (Fig. 13). — Stand erect, heels together, grasp the
handles overhead, and charge forward with the right foot. Return
to first position, and then charge with the left. Repeat, using the
right and left foot alternately.

EXERCISE IV. (Fig. 13). — Stand erect, heels together. Grasp the
handle overhead, and charge forward with the right foot, knee bent.
Remain in this position and bring the arms down to the sides so that
the arm and fore-arm may form a right angle. Still holding the
handles, thrust forward, first the right hand and then the left, until
the arm is straight. Repeat. Return to first position, then charge
forward with the left foot, performing the same movements as before.

EXERCISE V. (Fig. 13). — In this exercise we change to the pulleys
leading from the side posts, which can be used in several different
ways. 1st. Stand erect, heels together, facing one of the posts,
grasp the handle with the right hand, the ajm being extended, then
flex the fore-arm on the arm. Repeat Perform the same move-
ments with the left hand. 2cl. Stand with back to the post ; grasp
the pulley behind with the right hand, then gradually bring the
hand forward until it is extended in a straight line in front. Repeat.
Perform the same exercise with the left hand.

THK

VI. vFis:. l:M. -This exereise is espeeiallv adapted to the
Stirrups are so arranged that they can bo attaehed to the
pulleys overhead, aiul ean han^r down to within three or tour toot of
the floor. Place the foot in the stirrup, and then press down until it
touches the floor. Repeat Exercise the left foot in the same way.

EXERCISE VIL (Fig. 18V— This exercise requires a little attention
in the adjustment of the apparatus. Under the pulleys in the floor
aiv passed ropes whidi can be attached to the snap-hooks that hold
the handles overhead. Stoop forward with the knees stiff; and take
hold of the handles, and then raise the body to the erect position.
Repeat

EXERCISE Vin. (Fig. 18).— Sit on the floor or on a seat three or
four inches high ; bend forward, take hold of the handles, and per-
form the same movements that you would in rowing a boat

EXERCISE IX. (Fig. 18).— The trapeze can now be let down ; take
hold of it with both hands, sustaining the weight of the body with
the arms, then rotate the body first from right to left, then from left
to right alternately. This exercise is especially suitable for females.

F.XKKt-isK X. ^Kisr. i;;\— <,;ra<p the trape/e as before, bearing all
the weight with the arms : then draw the body up slowly until you
can place the chin over the bars. This requires strength of muscle,
and might strain if done too violently ; if slowly performed there is
no danger.

These are but a few of the exercises that can be practised with
this apparatus. As these become familiar they can easily be modi-
fied, and new ones can be arranged to meet the requirements of
particular cases. Host of the exercises described can be practised
with one hand so as to strengthen the muscles on one side.

29. Rest. — We cannot always be active: repose must
succeed labor. We obtain this rest partly by suspending
all exertion, as in sleep, and partly by a change of employ-
ment It is said that Alfred the Great recommended that
each day should be divided in the following manner:
"Eight hours for work, eight hours for recreation, and
eight hours for sleep." This division of time is as good as
any that could now be made, if it be borne in mind that,
when the work is physical, the time of recreation should

aft.'Needof tepoM? How do tre obtain rat ? Alfred the Great ! The ei«ht-
hoor diTfeion of UmoT

THK MI.'HCLKH.

be devoted to the improvement of the mind; and when
mental, we should then recreate by means of physical
exercise.

30. During sleep, all voluntary activity ceases, the rapid-
ity of the circulation and breathing diminishes, and the
temperature of the body falls one or two degrees. In con-
sequence, the body needs warmer coverings than during
the hours of wakefulness. During sleep, the body seems
wholly at rest, and the mind is also inactive, if we except
those involuntary mental wanderings which we call dreams*
Nevertheless a very active and important physical process
is going on. Nutrition, or the nourishing of the tissues,
now takes place. While the body is in action, the process
of pulling down predominates, but in sleep, that of build-
ing up takes place more actively. In this way we are re-
freshed each night, and prepared for the work and pleasures
of another day. If sleep is insufficient, the effects are seen
in the lassitude and weakness which follow. Wakefulness
is very frequently the forerunner of insanity, especially
among those who perform excessive mental labor.

31. All persons do not require the same amount of sleep,
but the average of men need from seven to nine hours.
There are well-authenticated cases where individuals have
remained without sleep for many days without apparent
injury. Frederick the Great required only five hours of
sleep daily. Bonaparte could pass days with only a few
hours of rest. But this long continued absence of sleep is
attended with danger. After loss of sleep for a long period,
in some instances, stupor has come on so profoundly, that
there has been no awaking.

32. There are instances related of sailors falling asleep

30. Cessation of voluntary activity ? Temperature of the body ? Consequence ?
Body and mind daring sleep ? Nutrition ? Describe it. Consequence of inroffi-
ci'rrj' rten -•

31. Amount of sleep in different persons? Cages? Frederick the Great?
Bonaparte? Instance* of Jong deprivation of sleep ?

32. Instance* of sailors ? French soldiers ? During torture 1

40 THE MUSCLES.

on the gun-deck of their ships while in action. On the
retreat from Moscow, the French soldiers would fall asleep
on the march, and could only be aroused by the cry, "The
Cossacks are coming !" Tortured persons are said to have
slept upon the rack in the intervals of their torture. In
early life, while engaged in a laborious country practice,
the writer not unfrequently slept soundly on horseback.
These instances, and others, show the imperative demand
which nature makes for rest in sleep.

QUESTIONS FOR TOPICAL REVIEW.

PAGE

1. What can yon state of the number and division of the muscles ? 25, 26

2. Describe the structure of the muscles 25, 26

3. Their arrangement in pairs and consequent action 2G

4. What is the difference between the motion called flexion and that called

extension ? 26

5. Describe their action, and state which are the more powerful 23

6. What is the difference between voluntary and involuntary muscles? 26

7. Illustrate the difference between the two 20

8. State all you can of the tendons or sinews 27

9. What is meant by contraction of the muscles ? 27, 28

10. In how many and what ways may contraction be effected ? 28

11. What is stated of after-death contraction ? 23

12. Wrhy cannot a muscle in life continue contracted a Ions: time ? 23

13. How then can the constant beating of the heart be explained ? 28

14. How docs the strength of a man compare with that of a horse ? 29

15. What can you state in relation to the relative strength of animals ?. ... 28, 29

16. What, in relation to physical strength ? 29

17. What, in relation to physical degeneracy ? 29, 30

18. What, in relation to the importance of exercise ? 30

19. What is the effect of exercise upon the heart, skin, and appetite ?. 30, 31

20. How docs exercise affect the current of the body's circulation ? 31

21 . How does judicious exercise affect the muscles ? , 31

22. What is stated of violent and spasmodic exercise ? 31

23. Of the exercise of walking ? 31, 32, 33

24 Of running, leaping, and other modes of exercise ? 3s

25. Of physical culture, in connection with out-door exercises ?

26. Of the importance of gymnastics in our schools and colleges ? 33, 34

27. Of the importance of rest from labor or exercise ? • • • - 38, 39

28. What processes take place during sleep ? »

29. What effects follow insufficient sleep ? 39

THE INTEGUMENT, OR SKIN. 41

CHAPTER III.
THE INTEGUMENT, OB SKIN.

The Integument — Its Structure — The Nails and Hair — The Complexion
— The Sebaceous Glands — The Perspiratory Glands — Perspiration
and its Uses — Importance of Bathing — Different kinds of Baths —
Manner of Bathing — The Benefits of the Sun — Importance of Warm
Clothing — Poisonous Cosmetics.

1. The Integument. — The skin is the outer covering
of the body. The parts directly beneath it are very sensi-
tive, and require protection. This is shown whenever by
accident the skin is broken, pierced, or torn off, the bared
surface being very tender, and painful to the touch. Nature
has provided the body with a garment that is soft, pliable,
close-fitting, and very thin, and yet sufficiently strong to
enable us to come in contact with the objects that sur-
round us, without inconvenience or suffering.

2. The Structure of the Skin. — When examined with
the aid of the microscope, the skin is found to be made up
of two layers — the outer and the inner. The inner one is
called the cutis, or true skin ; the outer one is the epider-
mis, or scarf-skin. The latter is also known as the cuticle.
These two layers are closely united, but they may be sepa-
rated from each other. This separation takes place when-
ever, from a burn, or other cause, a blister is formed;
a watery fluid is poured out between the two layers, and
lifts the epidermis from the true skin.

Of the two layers, the cuticle is the thinner in most parts
of the body, and has the appearance of a whitish mem-
brane. It is tough and elastic, is without feeling, and does

1 . What is the skin ? Parts directly beneath ? What is shown ?

2. Microscopic examination ? What is the cutis ? The cuticle ? Their union ?
How separated ? What further is said of the cuticle ?

42 THE INTEGUMENT, OR SKIN.

not bleed,when cut. Examine it more closely, and we observe
that it is composed of minute flat cells, closely compacted,
and arranged layer upon layer.

3. The outer layer is constantly being worn out, and
falls from the body in the form of very fine scales. It is,
also, continually forming anew on the surface of the inner
layer. Its thickness varies in different parts of the body.
Where exposed to use, it is thick, hard, and horn-like, as
may be seen on the soles of the feet, or on the palms of the
hands, especially of those who are accustomed to perform
much manual labor. This is an admirable provision for
the increased protection of the sensitive parts below the
skin against all extraordinary exposure. Even the liabil-
ities of these parts to injury, are thus kindly provided for
by " the Hand that made us."

4. The cutis, or true skin, lies beneath the epidermis,
and is its origin and support. It is firm, dense, elastic,
very sensitive, and is freely supplied with blood-vessels.
It is closely connected with the tissues below it, but may
be separated by means of a sharp instrument. The surface
of the cutis is not smooth, but is covered here and there
with minute elevations, called papillce. These are arranged
in rows, along fine lines, or ridges, such as those which
mark the palm and fingers ; their number is about 80 to
the square line (a line being one-tAvelfth of an inch).
These papillce contain the blood-vessels which carry the
supply of blood needed by the ever-wasting skin. They
contain nerves also, and are largely concerned in the
sense of touch; hence they are particularly abundant
where the touch is most delicate, as at the ends of the
fingers.

5. The Nails and Hair, — These are appendages of the

3. Wearing out of the cuticle ? What then ? Variety in thickness of cuticle r
How accounted for?

4. Location and office of the cutis? What further is said of it? Papillae?
Touch ?

5. What are the nails and hair ? The growth of the nail ? The rapidity of it3
growth 2 Accident to the nail ?

THE INTEGUMENT, OR SKIN.

43

skin, and although very unlike the cuticle as it appears on
the surface of the body, they are, in reality, modified forms
of that layer of the skin. The nail grows from a fold of
the cuticle at the root, and from the under surface. As
fast as it is formed, it is
constantly being pushed
outward. The rapidity of
its growth can be ascer-
tained by filing a slight
groove on its surface, and
noticing how the space be-
tween it and the root of
the nail increases, in the
course of a few weeks.
When the nail is removed
by any accident, it will be
replaced by a new one, if
the root be not injured.

6. The hairs are pro-
duced in a similar manner ;

5. The hair sac.
c. TRANSVERSE SECTION OF A HAIR.

Fig. 14.

o, b. THE ROOT op A HAIR.
the Skm forming depreS- i,2,3. The skin forming the hair sac. 4.

sions, or hair sacs, from
the bottom of which they
grow and are nourished (Fig. 14). They are found, of
greater or less length, on almost all parts of the surface,
except the palms of the hands and soles of the feet. On
certain parts of the body, they grow to great length ; on
other parts they are so short, that they do not rise beyond
the hair sac in which they originate.

7. The bulb, or root, from which the hair arises, is
lodged in a small pouch, or depression in the skin. The
shaft is the part which grows out beyond the level of the
skin. Its growth is altogether in one direction, in length
alone. The outer part of the hair is quite firm, while its

6. How are the hairs produced ? Difference in their length ?

7. Root of the hair ? Shaft ? Firmness and softness ofthe hair?

44 THE INTEGUMENT, OR SKIN.

interior is softer, and probably conveys the fluids by which
it is nourished. The hair is more glossy in health than at
other times.

8. The nail serves as a protection to the end of the
finger, and also enables us to grasp more firmly, and to
pick up small objects. The hair, too, is a protection to
the parts it covers. On the head, it shields the brain from
extremes of heat and cold, and moderates the force of blows
upon the scalp. On the body, it is useful in affording a
more extensive surface for carrying off the perspiration.

9. Complexion. — In the deeper cells of the cuticle
lies a pigment, or coloring matter, consisting of minute
colored grains. On this pigment complexion depends; and,
according as it is present in less or greater amount, occa-
sions the difference of hue, that exists between the light
and dark races of men, and between the blonde and bru-
nette of the white races. Freckles are due to an irregular
increase of coloring matter.

10. The sun has a powerful influence over the develop-
ment of this pigment, as is shown by the swarthy hue of
those of the white race who have colonized in tropical
climates. It is also well illustrated by the fact, thai
among the Jews who have settled in northern Europe,
there are many who are fair complex ioned, while those
residing in India, are as dark as the Hindoos ground them,

11. An Albino is a person who may be said to have nc
complexion: that is, there is an entire absence of coloring
matter from the skin, hair, and iris of the eye. This con-
dition more frequently occurs among the dark races, and
in hot climates, although it has been observed in almosl
every race and clime.

12. Sebaceous Glands. — There are in the skin certain

8. Office of the nail ? Of the hair? Give the illustrations.

9. On what doe? the complexion depend ">. Light and dark races ">. Freckles !

10. Influence of the sun ? How illustrated? Jews?

11. What is an Albino? Where are Albino* found ?

l!4. What are sebaceous glands ? How do they act? Sebaceous glands of th<
fkce ? How do they act ?

THE INTEGUMENT, OR SKIN. 45

small glands, which produce an oily substance, called se-
baceous matter. These glands are little rounded sacs,
usually connected with the hair-bulbs; and upon these
bulbs, they empty their product of oil, which acts as a,
natural and adequate dressing for the hair (4, Fig. 13). A
portion of the sebaceous matter passes out upon the sur-
face, and prevents the cuticle from becoming dry and hard.
The glands situated upon the face and forehead, open
directly upon the skin. In these, the sebaceous matter is
liable to collect, and become too hard to flow off naturally.

13. These glands on the face and forehead frequently
appear, on the faces of the young, as small black points,
which are incorrectly called "worms." It is true, that oc-
casionally living animalcules are found in this thickened
sebaceous matter, but they can only be detected by the aid
of the microscope. This sebaceous matter acts not only to
keep the skin flexible, and furnish for the hair an oily
dressing, but it especially serves to protect the skin and
hair, from the acridity arising from the perspiration.

14. The Perspiratory Glands. — The chief product
of the skin's action is the perspiration. For the forma-
tion of this, there are furnished countless numbers of
little sweat-glands in the true skin. They consist of fine
tubes, with globe-like coils at their deeper extremity. Their
mouths or openings may be seen with an ordinary magnifying
glass, upon the fine ridges which mark the fingers. These
tubes, if uncoiled, measure about one-tenth of an inch in
length. In diameter, they are about one three-hundredth
of an inch, and upon certain parts of the body there are not
far from three thousand of these glands to the square inch.
Their whole number in the body is, therefore, very great;
and, in fact, it is computed if they were all united, end to end.
their combined measurement would exceed three miles.

13. Black pointy called worms? Animalcules? Service performed by seba-
ceous matter?

14. Perspiration? Sweat stands? Of what do they consist? Dimension of
the tubes?

46 THE INTEGUMENT, OR SKIN,

15. The Sensible and Insensible Perspiration.—

The pores of the skin are constantly exhaling a watery
fluid; but, under ordinary circumstances, there is no
moisture apparent upon the surface, for it evaporates as
rapidly as it is formed. This is called insensible perspira-
tion. Under the influence of heat or exercise, however,
this fluid is excreted more abundantly, and appears on the
surface in the form of minute, colorless drops. It is then
termed sensible perspiration.

16. . Water is the chief component of this fluid, there
being about ninety-eight parts of water to. two parts of
solid matter. The quantity escaping from the body varies
greatly, according to the temperature of the air, the
occupation of the individual, and other circumstances.
The average daily amount of this excretion, in the adult,
is not far from thirty ounces, nearly two pints, or more
than nine grains each minute.

17. The Uses of the Perspiration. — Besides liber-
ating from the blood this large amount of water, with the
effete matter it contains, the perspiration serves to regulate
the temperature of the body. That is to say, as evapora-
tion always diminishes temperature, so the perspiration, as
it passes off in the form of fine vapor, cools the surface.
Accordingly, in hot weather this function is much more
active, and the cooling influence increases in proportion.
When the air is already charged with moisture, and does
not readily receive this vapor of the body, the heat of
the atmosphere apparently increases, and the discomfort
therefrom is relatively greater.

18. The importance of this excretion is shown by the
effects that often follow its temporary interruption, namely,
headache, fever, and the other symptoms that accompany

1 5. What is sensible perspiration ? Insensible perspiration ?

16. Components of perspiration? Upon what does perspiration depend?
Amount of perspiration daily ?

17. What does perspiration set free from the blood ? What other service does
perspiration perform ? Explain the process.

18. Effect of interruption of excretion ? What experiments are mentioned ?

THE INTEGUMENT, OR SKIN. 47

"taking cold/' When the perspiration is completely
checked, the consequences are very serious. Experiments
have been performed upon certain smaller animals, as rab-
bits, to ascertain the results of closing the perspiratory
tubes. When they are covered by a coating of varnish
impervious to water and gases, death ensues in from six to
twelve hours ; the attendant symptoms resembling those
of suffocation.

19. It is related that, at the coronation of one of the
Popes about three hundred years ago, a little boy was
chosen to act the part of an angel ; and in order that his
appearance might be as gorgeous as possible, he was cov-
ered from head to foot with a coating of gold foil. He was
soon taken sick, and although every known means were
employed for his recovery, except the removal of his fata!
golden covering, he died in a few hours.

20. The Importance of Bathing. — From these con-
siderations, it is evident that health must greatly depend
upon the free action of the skin. " He who keeps the skin
ruddy and soft, shuts many gates against disease." When
the watery portion of the perspiration evaporates, the solid
matter is left behind on the surface. There, also, remain
the scales of the worn-out cuticle, and the excess of seba-
ceous matter. In order to secure the natural action of the
skin, these impurities require to be removed by the frequfcnt
application of water.

21. In warm climates, and during hot weather, ablution
should be more frequently practised. For a person in
good health, a daily cold bath is advisable. To this should
be added occasionally a tepid bath, with soap, Avater alone
not being sufficient to remove impurities of a greasy nature.
Soap facilitates this, by forming with such substances a
chemical mixture, which is readily soluble in water, and is
by it removed from the body.

19. Give the story in relation to the boy covered with gold foil.

20. Give the quotation. Perspiration ?

2 1 . Ablution in warm climates '- What advice i? iriven *

48 THE INTEGUMENT, OR SKIN.

22. There is a maxim by the chemist Liebig, to the effect,
that the civilization of a nation is high, in proportion to
the amount of soap that it consumes ; and that it is low, in
proportion to its use of perfumes. In some degree, we may
apply the same test to the refinement of an individual.
The soap removes impurity ; the perfume covers, while
retaining it.

23. The different kinds of Baths. — All persons are
not alike able to use the cold bath. When the health is
vigorous, and the system does not feel a shock after such a
bath, a prompt reaction and glow upon the surface will
show that it is beneficial. Where this pleasurable feeling
is not experienced, but rather a chill and sense of depres-
sion ensues, we are warned that the system will not,
with impunity, endure cold bathing.

24. It should also be borne in mind, that the warm or hot
bath cannot be continued so long, or repeated so frequently
as the cold, on account of the enervating effect of unusual
heat so applied to the body. For persons who are not in
robust health, one warm bath each week is sufficient ; this
class should be careful to avoid every extreme in reference
to bathing, clothing, and whatever greatly affects the actioi!
of the skin.

25. Sea-bathing is even more invigorating than fresh-
water bathing. Those who cannot endure the fresh water,
are often benefited by the salt-water baths. This may be
accounted for, in part, by the stimulant action upon the
surface, of the saline particles of the sea-water; but the
exciting scenes and circumstances of sea-bathing also exert
an important influence. The open-air exercise, the rolling
surf, the genial weather, and usually the cheerful company,
add to its intrinsic benefits.

22. Liebig'p maxim ? What further in added ?

23. What'is said about cold bathinir ?

24. What Is Mid about warm bathing?

25. What is said about sea-bathing ?

THE INTEGUMENT, OR SKIN. 49

26. Time and Manner of Bathing. — A person in
sound health may take a bath at almost any time, except
directly after a full meal. The most appropriate time is
about three hours after a meal, the noon-hour being proba-
bly the best. For the cold bath, taken rapidly, no time is
better than immediately after rising. Those beginning the
use of cold baths should first try them at 70° Fahr., and
gradually use those of a lower temperature. From five to
twenty minutes may be considered the proper limit of time
to remain in a bath ; but a sensation of chilliness is a signal
to withdraw instantly, whether at home, or at the sea-side.
Two sea-baths may be taken daily ; one of any other kind
is sufficient.

27. The body should be warm, rather than cold, whei)
stepping into the bath; and after it, the skin should be
thoroughly dried with a coarse towel. It is best to continue
friction until there is a sensation of warmth or "glow"
throughout the entire surface. This reaction is the test
of the good effects of the bath. If reaction is still incom-
plete, a short walk may be taken, especially in the sunshine.
It is very congenial, however, both to health and comfort,
to rest for a short time directly after bathing, or to take
some light refreshment. This is better than severe exer-
cise or a full meal.

28. Bathing among the Ancients. — The Romans
and other nations of antiquity made great use of the
vapor-bath as a means of preserving the health, but more
particularly as a luxury. Their method was not unlike
that employed in northern Europe at the present day.
The public baths of Rome and other cities are among the
grandest and most interesting monuments of ancient
luxury and splendor; and from their ruins have been re-
covered some of the most beautiful works of art.

26. What is gaid as to the time and manner of bathing ?

27. Condition of the body when bathing? Direction, after bathing?

28. Bathing among the ancients? Bath? of Rome?

3

50 THE INTEGUMENT, OR SKIN.

29. The Thermae, as the baths of Rome were called,
were of great extent, built very substantially, and orna-
mented at vast expense. They were practically free to all,
the cost of a bath having been less than a cent. It is
related that some persons bathed seven times a day. After
the bath their bodies were anointed with perfumed oil. If
the weather was fine, they passed directly from the Thermae
into the gymnasium, and engaged in some gentle exercise
previous to taking the midday meal. Between two and
three in the afternoon was the favorite hour for this ancient
luxury. Swimming was a favorite exercise, and a knowl-
edge of it was regarded as necessary to every educated man.
Their common expression, when speaking of an ignorant
person, was, " He can neither read nor swim."

30. The Sun-Bath. — Some also were accustomed daily
to anoint themselves, and lie or walk in apartments ar-
ranged for the purpose, with naked bodies exposed to the
direct rays of the sun. There is an interesting allusion to
this practice, in a letter of the younger Pliny to the his-
torian Tacitus, describing the destruction of Pompeii by
an eruption of Vesuvius. " My uncle," (Pliny the elder,)
"was at that time in command of the fleet at Misenum.
On the 24th of August, about one in the afternoon, my
mother desired him to notice a cloud which seemed 6f un-
usual shape and dimensions. He had just returned from
talcing the benefit of the sun, and after a cold bath, and a
slight repast, had retired to his study." Then follows a
description of the destruction of Pompeii, and the death
of the elder Pliny.

31. We may judge somewhat of "the benefits of the
sun," by observing the unnatural and undeveloped condi-
tion of plants and animals which are deprived of light.
Plants become blanched and tender ; the fish of subterra-

29. After the bath ? Swimming among the ancients *

30. The Sun-bath ? The story of Pliny ?

3 1 . Benefit of the pun ? Eftx-et upon plants * Skin ?

THE INTEGUMENT, OR SKIN. 51

nean lakes, where no light enters, are undersized, and have
no eyes; tadpoles kept in the dark do not develop into
frogs; men growing up in mines are sallow, pale, and
deformed. Besides the well-known effect of solar light in
tanning the skin, it also makes it thicker and better able
to resist exposure; though the complexion may be thereby
injured, the health gains more than compensates for the
loss of beauty. "To make good the loss of the lily, where
the sun has cast his ray, he seldom fails to plant the rose."

32. Clothing. — In reference to clothing, we are far
more apt, in our changeful climate, to use too little than
too much. An aphorism of Boerhaave, worth remember-
ing, if not of adopting, is, "We should put off our winter
clothing on midsummer's day, and put it on again the day
after." He also says, "Only fools and beggars suffer from
the cold ; the latter not being able to get sufficient clothes,
the others not having the sense to wear them." The prac-
tice of exposing the limbs and necks of young children,
for the alleged purpose of "hardening" them, is quite
hazardous. It is not to be denied that some seem to be
made tough by the process ; but it is so only with the rugged
children, the delicate ones will invariably suffer under this
fanciful treatment. As has been stated before, the skin is
constantly acting, by night as well as by day. It is there-
fore conducive both to cleanliness and comfort to change
entirely the clothing on retiring for the night. The day-
clothing should be aired during the night, and the bedding
should be aired in the morning, for the same reason.

33. Poisonous Cosmetics. — The extensive use of
cosmetics for the complexion is a fertile source of disease.
The majority of these preparations contain certain poison-
ous mineral substances, chiefly lead. Now, the skin
rapidly absorbs the fine particles of lead, and the system

32. Direction about clothing? Exposing limbs of children ? Clothing, night
and day ?

33. Cosmetics ? Painters' colic ?

52 THE IXTEGUMEXT, OR SKIX.

experiences the same evil effects that are observed among
the operatives in lead works and painters, namely, "paint-
ers' colic," and paralysis of the hands, called " wrist-drop."
34. Certain hair-dyes also contain lead, together with
other noxious and filthy ingredients. These do not work
as great harm as the cosmetics, since they are purposely
kept away from the skin, but they rob the hair of its
vitality. Eye-washes, too, are made from solutions of lead,
and many an eye has been ruined by their use. They de-
posit a white metallic scale on the surface of the eye, which
becomes a permanent obstruction to the vision.

QUESTIONS FOR TOPICAL REVIEW.

PAGE

1. What are the characteristics of the skin, and what office does it perform ? 41

2. What can you state of the structure of the skin ? 41

3. Describe the cuticle aiid tell its use 41, 42

4.- Describe the cutis or true skin and tell its use 42

5. What can you state of the nature and growth of the nail ? 42, 43

6. Of the nature and growth of the hair ? 4:2, 43, 4 1

7. Of the offices performed by the nails and hair * 44

8. How is the difference in complexion in different persons accounted for ?. 44

9. How is the presence of freckles accounted for ? 44

10. How does Nature provide a dressing for the hair ? 44, 45

11. What other service do the sebaceous glands perform ? 45

12. State what you can of the perspiratory gland* 45

1H. What is the difference between sensible and insensible perspiration ? . . . 46

14. State the uses and importance of perspiration 46, 47

15. What impurities gather naturally on the skin ? 47

16. Repeat what is said of the importance of bathing 47, 48

17. When should we indulge in cold, warm, and sea bathing ? 48, 49

18. What is the effect in each case ? 48

1H. What directions are given as to the time and manner for bathing ? 49

20. What is related of bathing among the ancients ? 49, 50

21. What, is related to show the antiquity of snn-bathing ? 50

22. What are the effects of snn-bathing ? -rA 51

23. What directions are given in relation to clothing the body ? , 51

24. What can you state of poisonous cosmetics ? 51,52

25. Of hair-dyes and eye-washes? 52

THE CHEMISTRY OF FOOD. 53

CHAPTER IV.
THE CHEMISTRY OF FOOD.

The Source of Food — Inorganic Substances — Water — Salt — Lime — Iron
— Organic Substances — Albumen, Fibrin, and Casein — The Fats or
Oils — The Sugars, Starch, and Gum — Stimulating Substances —
Necessity of a Regulated Diet.

1. The Source of Food. — The term, food includes all
those substances, whether liquid or solid, which are neces-
~ary for the nourishment of the body. The original source
of all food is the earth, which the poet has fitly styled the
" Mother of all living." In her bosom, and in the atmos-
phere about her, are contained all the elements on which
life depends. But man is unable to obtain nourishment
directly from such crude chemical forms as he finds in the
inorganic world. They must, with a few exceptions, be
prepared for his use, by being transformed into new and
higher combinations, more closely resembling the tissues
of his own body.

2. This transformation is effected, first, by the vegetable
world. But all plants are not alike useful to man ; while
some are absolutely hurtful. Accordingly, he must learn
to discriminate between that which is poisonous and that
which is life-supporting. Again, all parts of the same
plant or tree are not alike beneficial: in some, the fruit,
in others, the leaves, and in others, the seeds only are
'sufficiently refined for his use. These he must learn
to select ; he must also learn the proper modes of prepar'
ing each kind for his table, whether by cooking or othe
processes.

1 . The term food ? Source of food ? Need of preparing: food ?

2. Usefulness and hurtfulness of plants ? What then must man do ? Parti? of
the same plant or tree ?

54 THE CHEMISTRY OF FOOD.

3. Again, certain forms of the vegetable creation which
are unfit, in their crude state, for man's food, and which he
rejects, are chosen as food by some of the lower animals,
and are, by them, made ready for his use. Thus the bee
takes the clover, that man cannot eat, and from it collects
honey. The cattle eat the husks of corn and the dried
grass, that are by far too coarse for man, and in their own
flesh convert them into tissues closely resembling his mus-
cular tissue. In this way, by the aid of the transforming
processes of the vegetable and animal creations, the simple
chemical elements of the mineral kingdom are elaborated
into our choice articles of food.

4. Tnorganic Substances. — The substances we use as
food are classified as organic and inorganic. By organic
substances are meant those derived from living forms, such
as vegetables and animals. Inorganic substances are those
simpler inanimate forms which belong to the mineral
kingdom. The former alone are commonly spoken of as
food, but the latter enter very largely into the constitution
of the body, and must therefore be present in our food.
With the exception of two articles, water and common
salt, these substances only enter the system when blended
with organic substances.

5. Water. — Water, from a physiological point of view, is
the most important of all the articles of food. It is every-
where found in the body, even in the bones and the teeth.
It has been computed that as large a proportion as two-
thirds of the body is water. The teeth, the densest of the
solids in the human system, contain ten per cent, of water.
The muscles, tendons, and ligaments are more than half
water; for it is found that they lose more than half their

3. Certain forms of vegetable creation? Example of the bee? Cattle? The
inference ?

4. What classification ? Define organic substances. Inorganic. Organic,
how spoken of? The inorganic ? Water and salt ?

5. Water in physiology ?"' Where found ? Computation? Water in the teeth?
Muscles, tendons, and ligaments ? How ascertained? Water in the fluids of the
body ? What is the advantage ?

THE CHEMISTRY OF FOOD. 55

weight when dried with moderate heat. But it is in the
fluids of the body that water is found most abundantly.
It gives to them the power of holding a great variety of
substances in solution, and is the great highway by which
new supplies are conveyed to the point where they are
required, and by which old particles of matter, that have
served their uses, are brought to the outlets of the body to
te thus removed from the system.

C. Man can remain a longer time without solid food
than without water.- He may be deprived of the former
for ten to twelve hours without great suffering, but depri-
vation of water for the same length of time will produce
both severe pain and great weakness. The food should contain
not less than two parts of water to one of solid nutriment.
Water constitutes the great bulk of all our drinks, and is
also a large constituent of the meats, vegetables, and fruits
which come upon the table. Fruits, especially, contain it
in great abundance, and, in their proper season, furnish
most agreeable and refreshing supplies of the needed fluid.

7. Common Salt. — Salt, or sodium chloride, as an
article of food, is obtained chiefly from the mineral king-
dom; although plants contain it in small quantities, and
it is also found in the tissues of nearly all animals used
as food. In the human body, it is an ingredient of all
the solids and fluids. The importance of salt to animal
life in general, is shown by the great appetite for it mani-
fested by domestic animals, and also by the habitual resort
of herds of wild beasts to the " salt-licks" or springs. In
those parts of the world where salt is obtained with diffi-
culty, man places a very high price upon it.

8. Experiments upon domestic animals show that the
withdrawal of salt from their food, not only makes their

6. Length of time man can do without food or water ? Give the comparison ?
Bulk of drinks ? Constituent, of meats?, etc. ? Fruits ?

7. Salt, how obtained ? Where found? In the human body? Importance oi
^alt ? What else can yon st ato of the value of salt ?

8. Experiments upon animals?

55 IHE CHEMISTRY OF FOOD.

hides rough and causes the hair to fall out, but also inter-
feres with the proper digestion of food. If it be withheld
persistently, they become entirely unable to appropriate
nourishment, and die of starvation.

9. Salt is usually taken into the system in sufficient
quantities in our food. Even the water we drink often
has traces of it. The habitual use of much salt in cook-
ing, or as a seasoning at the table, is not wise; and while
it may not lead to consumption, as some writers declare, it
is a bad habit in itself, and leads to the desire for other and
more injurious condiments.

10. Lime. — This is the mineral substance which we
have spoken of before as entering very largely into the com-
position of the bones. It is the important element which
gives solidity and permanence to the framework upon
which the body is built. Calcium tri-phosphate, or " bone-
earth," is the chief ingredient of the bones and teeth, but
is found in the cartilages and other parts of the body in
smaller quantities.

11. How does this substance find its way into the body?
Meat, milk, and other articles obtained from the animal
kingdom contain it, and it is abundantly stored away also
in the grains from which our bread is made, in wheat, rye,
and Indian corn. In early life, while the body is growing,
the supplies of this substance should be carefully provided.
The evil effects of the deprivation of it are too often and
painfully evident in the softening of the bones, and in the
predisposition to curvature of the spine — deformities which
are most deplorable and which continue through life.

12. Iron. — This substance is probably the most abun-
dant and widely diffused of the metals. It is found in

9. Salt, how taken into the system ? Its use in cooking ? Consumption ?

10. Lime in the bones? What does it impart ? Chief ingredient ot the bones
and teeth ? Where else found ?

11. How does lime find its way into the body? Early life? Effect of its
deprivation ?

12. Iron, its abundance and diffusion ? Where found ? What part of the blood
is it ? How supplied to the system ? In case of loss of blood or wasting disease ?

THE CHEMISTRY OF FOOD. 57

most of the vegetables, and is a very important component
of animal tissues. It enters into the composition of hu-
man blood in about one part per thousand. Ordinarily,
the food conveys to the system enough iron for its use, but
it must sometimes be introduced separately as a remedy,
especially after great loss of blood, or after some wasting
disease. Under its influence the blood seems to be
rapidly restored, and a natural color of the lips and skin
replaces the pallor caused by disease.

13. Other Inorganic Substances. — In addition to
the substances mentioned, the mineral kingdom supplies
compounds of soda, potash, and magnesia, which are es-
sential for the use of the body. They occur in small
quantities in the body, and enter it in combination with
the various articles of diet.

14. Organic Substances. — These substances are derived
from the vegetable and animal creations. They comprise
all those articles which are commonly spoken of as " food,"
and which are essential to sustain the body in life and
strength. They are divided into three groups, namely:
the Albuminoid substances, the Fats, and Sugars.

15. The Albuminoids. — This class includes three im-
portant nutritive substances — (1) Albumen, which gives it
its name; (2) Fibrin, including gluten; and (3) Casein.
These compounds constitute a large part of the human
body, and the food contains them in proportionally large
quantities. Their importance is so great, and the system
so promptly suffers from their absence, that they have been
styled the " nutritious substances." The properties which
they hold in common are, that they do not crystallize, and
have a jelly-like form, except when heat is applied to them,
when they harden, or coagulate.

1 3. Soda, potash, and magnesia ? How do they occur ?

1 \. Onranic eubstances, whence derived ? What do they comprise ? Groups :.
li. The Albuminoid class, includes what? These compounds conatituta
what? The food '? Their importance? Their properties ?

3*

58 THE CHEMISTRY OF FOOD.

16. They likewise decompose, or putrefy, under the influ-
ence of warmth and moisture. Hence the decay of all
dead animal tissues. Cold arrests this process. It is well
known that milk, eggs, and the like, " keep" much longer
in winter than at other seasons. The bodies of elephants,
caught in the ice many hundred years ago, are occasion-
ally borne by the icebergs to the coast of Siberia, com-
pletely frozen, but preserved almost perfectly in form and
limb.

17. Albumen exists in milk, meat, the grains, and the
juices of many plants; but the purest form is obtained
from the white of egg. When we consider that an egg is
composed chiefly of albumen and water — namely, six parts
in seven; and when we also consider the numerous, diverse,
and complex tissues — the muscles, bones, internal organs,
bill, claws, and feathers — with which the chick is equipped
on leaving his shell, we are impressed with the importance
of these apparently simple constituents of the food and
body.

18. Fibrin is derived from meats, and exists in the
blood both of man and the lower animals. Gluten, or
vegetable fibrin, resembles closely true fibrin, and is abun-
dantly furnished in wheat and other grains from which
flour is commonly made. Animal fibrin coagulates spon-
taneously when it is removed from the body, and thus
causes the "clotting" of the blood.

19. Casein is the curdy ingredient of milk, and a highly
important food-substance. Its coagulation in milk takes
place not from heat, but by the addition of an acid, and
also when milk becomes sour from exposure to the air. It
is commonly effected, however, by introducing a piece of
rennet, a preparation made from a calf's stomach. The
curds, or casein, may then be separated from the wliey,

1 6. Decomposition ? Effect of cold ? Illustrations ? Elephants ?

17. In what substance!* does albumen exist ? What further is said of the e<*s *

18. Fibrin, gluten, clotting of the blood ?

19. Casein ? Its coagulation ? Effect of rennet ? Making of cheese?

THE CHEMISTRY OF FOOJ). 50

and made into cheese, by pressing it sufficiently to drive
off the water.

20. The Fats or Oils. — This is the second group of
organic foods. Those which are more solid are called fats :
the more fluid ones are the oils. Oleaginous substances
are supplied in both animal and vegetable food; but, from
whatever source derived, they are chemically much alike.
They are insoluble in water, and yet they unite readily
with the watery fluids of the body, and are by them con-
veyed to its various parts for their nourishment. This is
due to their property of "emulsifying;" that is, they are
held in suspension, in a finely divided state, in water. Or-
dinary milk is an example of an emulsion. We know that
it contains fat ; for butter is obtained from it, and, under
the microscope, the minute oil-globules may be distinctly
seen.

21. In our country and climate, and also in colder
climates, fatty articles of food are principally derived from
the animal creation, such as meat or flesh, milk and butter.
But most of the bread-stuffs contain more or less fat or oil;
Indian meal as much as nine parts in a hundred.

22. Among persons living in cold climates, the appetite
for oleaginous food is especially eager ; and they require
large quantities of it to enable them to resist the depress-
ing influences of cold. Since vegetation is scanty and
innutritions, and the waters of the frozen regions abound
in animal life, they must rely wholly upon a diet derived
from the latter source. The Esquimaux consumes daily
from ten to fifteen pounds of meat or blubber, a, large
proportion of which is fat. The Laplander will drink
train-oil, and regards tallow-candles as a great delicacy.
In hot climates, on the contrary, where flourish the olive

20. What are the fata ? The oils ? How supplied? How alike? Emulsifying?
Example * How do we know it?

21. Whence are fatty articles of food derived?

22. Appetite of persons in cold climates ? What do they require ? Upon what
must they rely ? Why? The Esquimaux? Laplander? Olive and palm ?

60 THE CHEMISTKY OF FOOD.

and the palm, this kind of food may be obtained from
vegetable sources in abundant quantities.

23. The Sugars, or the Saccharine Substances. —
These constitute the third, and last, group of the organic
substances, which are employed as food. This group em-
braces, in addition to the different kinds of Sugar, the
varieties of starch and gum, from whatever source derived.
The two substances last named do not, at first sight, pre-
sent many points of similarity to sugar ; but they closely
resemble it in respect to their ultimate chemical composi-
tion, being made up of the same elements, in nearly the
same proportions. And their office in the system is the
same, since they are all changed into sugar by the processes
of digestion.

* 24. Sugar is chiefly of vegetable origin; the animal
varieties being obtained from honey and milk. The most
noticeable characteristic of this substance is its agreeable,
sweet taste, which makes it everywhere a favorite article of
food. But this quality of sweetness is not possessed by all
the varieties of sugar in the same degree ; that obtained
from milk, for instance, has a comparatively feeble taste,
but rather imparts a gritty feeling to the tongue. The
other important properties of sugar are, its power to
crystallize when evaporated from watery solutions, such as
the juices of many plants ; a tendency to ferment, by which
process alcohol is produced; and a ready solubility in
water. This latter quality renders it very easy of digestion,
and more so than any other of the saccharine, group. It is
computed that the annual production of sugar, in all parts
of the world, is more than one million of tons. The kind
of sugar that is in ordinary use, in this country, is prepared
from the juice of the sugar-cane, which contains eighteen
per cent, of sugar. In France it is manufactured from the

23. Which are the third of the organic groups? What do they embrace?
Points of resemblance ?

24. Origin of the sugars? Ordinary eugar? Beetroot? Maple-sugar? Grape-
r-ugar? Cane-sugar?

THE CHEMISTRY OF FOOD.

Gi

beet root, which holds about nine per cent. ; the maple- tree
of our climate yields a similar sugar. The sweet taste of
fruits is due to the presence of grape-sugar: the white
grains seen on raisins belong to this variety. Cane-sugar
is more soluble than the latter, and has twice the sweeteu-
;ng power.

25. Starch. — This is the most widely distributed of
the vegetable principles.
It is tasteless, inodorous,
and does not crystallize.
It consists of minute
rounded granules, which,
under the microscope,
reveal a somewhat uni-
form structure (Fig. 15).
Starch will not dissolve
in cold water, but in
boiling water the small
grains burst open, and
may then be dissolved
and digested.

26. The bread stuffs, wheat, corn, and rye flours, are
more than one-half starch. Rice, which is the "staff of
life" to one-third of the human family, contains eighty
per cent. Unripe fruits have much starch in them,
which renders them indigestible when eaten uncooked;
for the grains of raw starch are but slightly acted upon
within the body. But, under the potent chemistry of the
sun's ray, this crude material is converted into sugar.
Thus are the fruits prepared by the careful hand of
Nature, so that when ripe they may be freely used without
further preparation.

27. Gum is commonly found in those articles which

25. Starch, how widely distributed? Its qualities? Its constituents? Its
solubility ?

26. How much starch in bread-stuffs ? In rice ? Unrine fruits? Ripe fruits?

27. Gum, where found ? Its composition ? Gum Arabic- ?

FIG. 15.— GRANULES OF POTATO STAHCH.

62 THE CHEMISTRY OF FOOD.

also contain starch ; and has the same chemical composi-
tion as the latter, but is much less nutritious. In the
East, gum-arabic and similar substances are largely em-
ployed as food. Persons who travel by caravan across vast,
sandy deserts, find such substances well adapted to their
wants, since they are not perishable, and are easily packed
and carried.

28. Stimulating Substances. — The three classes of
food-principles already considered — the Albuminoids, the
Fats, and the Sugars — comprise all the more important
organic ingredients of our food. There are, besides, a
great variety of coloring and flavoring matters that stim-
ulate or increase the appetite for food by appealing to the
eye and taste; but they are not nutritious, and are quickly
separated from the truly useful substances, and do not
long remain in the body. Among these may be classed
spices, flavors of fruits, tea, coffee, and vegetable acids.

29. Necessity of a Regulated Diet.— A great vari-
ety of experiments have been tried in order to test the rela-
tive value of the different nutritive principles. They have
been practised to some extent upon man, but chiefly upon
those inferior animals which require a similar diet to man.

30. By this means it has been demonstrated that — first,
when any one of these substances is eaten exclusively, the
body is imperfectly nourished, and life is shortened. Dogs
fed exclusively upon either albumen, fat, or sugar, soon die
of starvation. Second, a diet long deprived of either of
these principles, is a fertile cause of disease; for example,
on ship-board, where fresh vegetables are not dealt out for a
long period, scurvy becomes prevalent among the sailors.
They are, however, to a certain extent mutually convertible,
and thus the missing article is indirectly supplied. For

28. The three classes of food principles ? What besides? What is ?aid of
them ? Name the articles not nutritions.

29. What is said of experiments that have been tried ?

30. What has been demonstrated in the first place? Example? Second de-
monstration ? Example ? Give the illustration in relation to convertibility.

THE CHEMISTEY OF FOOD. 63

instance, sugar changes to fat in the body; and hence, as
is well known, the " hands" on a sugar plantation grow
fat during the sugar season, by partaking freely of the
ripened juices of the cane.

31. That is the best diet therefore which contains some
of each of these principles, in due proportion; and that is
the worst which excludes the most of them. The cravings
and experience of man had unerringly guided him to a
correct regulation of his diet, long before the chemistry
of food was understood; so that his ordinary meals
long ago combined these various principles, the necessity
and value of which are now explained.

QUESTIONS FOR TOPICAL REVIEW.

PAGE

1. What is understood by the term food ? 53

2. What can yon state in relation to the source of food ? 53

3. What discriminations and selections are necessary ? 53, 54

4. How can you tell the organic from the inorganic substances 51 54

5. What relative position does water hold as an article of food ? 54

6. In what parts of the body is water found ? 54, 55

7. In what articles that we eat is it found ? 55

8. If you were required to go without water or solid food for a number of days,

which would you prefer to have, and why ? 55

9. What can you state of the importance of salt as an article of food ? 55, 56

10. How abundant is salt, and how does it find its way into the human sys-

tem ? 55, 56

11. What can you state of the importance of lime in the body ? 56

12. What, of the importance of iron ? 56, 57

13. What furthor ie stated of other inorganic substances ? 57

14. What in relation to organic substances ? 57

15. What can you state in relation to the albuminoids ? 57, 58

16. What, in relation to albumen ? ^

17. What, in relation to casein ? ^ 59

18. In relation to the fats or oils, and how generally consumed ? 59, 60

19. What do we understand by the sugars or saccharine substances ? 60

20. State what yon can of fmsrar— its origin and various qualities fiO- fit

21 . Of starch— its varieties and qualities • 61

22. Of the abundance of starch, and its importance as a food principle 61

23. What is stated In relation to stimulating substances ? 62

24. Of the necessity for regulation in diet? 62, 63

64 FOOD AND DRINK.

CHAPTER V.
FOOD AND DRINK.

Necessity for Food — Waste and Repair — Hunger and Thirst — Amount
of Food — Renovation of ike Body — Mixed Diet — Milk — Eggs — Meat
—Cooking— Vegetable Food— Bread— Tfie Potato— Fruits— Purity
of Water — Action of Water upon Lead — Coffee, Tea, and Clwcolate
—Effects of AlcoJwl.

1. Necessity for Food. — Activity is everywhere fol-
lowed by waste. The engine uses up coal and water to
produce motion, the stream wears away its bank, the
growing corn-blade draws tribute from the soil. When the
human body acts, and it is always in action during life, some
of its particles are worn out and thrown off. This waste
must constantly be repaired, or the body suffers. In this
fact is seen the necessity for food. The particles, thus worn
out, being henceforth useless, are removed from the body.
Our food and drink are rapidly transformed into a new
supply of living, useful material, to be in turn used up
and replaced by a fresher supply.

2. Waste and Repair. — In this way the healthful
body, though always wasting, is always building up, and
does not greatly change in size, form, or weight. At two
periods of life the processes of waste and repair are not ex-
actly balanced. In early life the process of building up is
more active, and in consequence the form is plump, and
the stature increases. Repair now exceeds waste. On the
other hand, when old age comes on, the wasting process is
more active, the flesh and weight diminish, the skin falls
in wrinkles, and the senses become dull. Only during the
prime of life — from about twenty to sixty years of age — is
the balance exact between loss and gain.

1 . What follows activity ? Examples ? Necessity for food ?

2. Give the theory in relation to waste and repair.

FOOD AND DRINK. 65

3. Hunger and Thirst. — When the system is deprived
of its supply of solid food during a longer time than usual,
nature gives warning by the sensation of hunger, to
repair the losses that have taken place? This sensation
or pain appears to be located in the stomach, but it is really
a distress of the system at large. Let a sufficient quantity
of nourishment be introduced into the system in any other
way than by the mouth, and it will appease hunger just as
certainly as when taken in the usual manner.

4. The feeling of thirst, in like manner, is evidence that
the system is suffering from the want of water. The
apparent seat of the distress of thirst is in the throat ; but
the injection of water into the blood-vessels is found to
quench thirst, and by the immersion of the body in water,
the skin will absorb sufficient to satisfy the demands of the
system. The length of time that man can exist without
food or drink is estimated to be about seven days. If water
alone be supplied, life will last much longer ; there being
cases recorded where men have lived twenty days and over,
without taking any solid food.

5. Quantity of Food. — The quantity of food required
varies greatly, according to the individual and his mode of
life. The young, and others who lead active lives, or who
live in the open air, require more food than the old, the
inactive, or the sedentary. Those who live in cold regions
require more than the inhabitants of hot climates. Habit,
also, has much to do with the quantity of food required.
Some habitually eat and drink more than they actually
need, while a few eat less than they should.

6. The average daily quantity of food and drink for a
healthy man of active habits is estimated at six pounds.
This amount may be divided in about the following pro-

3. System deprived of food? Warning? What is the pain ? How proved ?

4. Feeling of thirst? Seat of the pani ? How proved? Time a person can
exist, without food ?

5. Amount of food required? The young and others? Those living in hot
and cold climates ? Habits *

6. Quantity of food daily ? How divided ? Compare with the weight of t lie body ?

66 FOOD AND DRINK.

portions: the mineral kingdom furnishes three and one-
half pounds, including water and salt; the vegetable king-
dom, one and one-half pounds, including bread, vegetables,
and fruits; the animal kingdom, one pound, comprising
meat, eggs, butter, and the like. This quantity is about
one twenty-fourth the weight of the body, as it is generally
computed ; the average weight of an adult man being placed
at 140 pounds. A man, therefore, consumes an amount of
solid and liquid nutriment every twenty-four days equal
in weight to that of his body, a corresponding amount
being excreted, or removed from the system in the same
time.

7. Renovation of the Body.— By this process, so far
as weight is concerned, the body might be renewed every
twenty-four days; but these pounds of food are not all real
nutriment. A considerable portion of that which we eat
is innutritions, and though useful in various ways, is not
destined to repair the losses of the system. An opinion
has prevailed that the body is renewed throughout once in
seven years ; how correct this may be it is not easy to
decide, but probably the renovation of the body takes
place in a much shorter period. Some parts are very
frequently renewed, the nutritive fluids changing more or
less completely, several times during the day. The muscles,
and other parts in frequent exercise, change often during a
year ; the bones not so often, and the enamel of the teeth
probably never changes after being once fully formed.

8. Mixed Diet. — The habits of different nations in
respect to diet exhibit the widest and strangest diversity.
The civilized, cook their food, while savages often eat
it in a raw state. Some prefer it when fresh, others allow
it to remain until it has become tainted with decay.
Those dwelling in the far north subsist almost wholly on

- 7. How often then might the body be renewed? Why is it not? Opinion?
How correct ? What further is stated ?
8. Habits of nations? Give the different cases.

FOOD AND DRINK. 67

animal food, while those living in hot climates have boun-
tiful supplies of delicious fruits with which to satisfy all
their bodily wants. One race subsists upon the banana,
another upon the blubber of seals. In temperate climates,
a diet composed partly of vegetable and partly of animal
food is preferred.

9. The important point to consider is, however, not one
of origin, but whether the chemical principles (mentioned
in the last chapter) enter into the composition of the diet.
A purely vegetable diet may be selected which would contain
all the principles necessary to sustain life. It is recorded of
Louis Cornaro, a Venetian noble, that he supported himself
comfortably for fifty-eight years on a daily allowance of
twelve ounces of vegetable food, and about a pint of light
wine. On the other hand, the food of John the Baptist,
consisting of "locusts and wild honey/' is an example of
the sustaining power of a diet chiefly animal in its origin.

10. In our climate, those who lead active lives crave an
allowance of animal food; and it has been found by ex-
perience that with it they can accomplish more work and
are less subject to fatigue, than without it. Among na-
tions where an exclusively vegetable diet is employed, indi-
gestion is a disorder especially prevalent.

11. The necessity for occasionally changing or varying
the diet, is seen in the fact that no single article comprises
all the necessary principles of food, and that the contin-
uous use of any one diet, whether salt or fresh, is followed
by defective nutrition and disease. There is one exception
to this rule : in infancy, milk alone is best calculated
to support life ; for then the digestive powers are incom-
pletely developed, and the food must be presented in the
simplest form possible. It should also be remembered

9. The point to consider? Vegetable diet? Louis Cornaro ? John the Bap
tist ?

1 0. What has been found in our climate ? Exclusive vegetable diet ?

11. Necessity for change in diet? Continuous use of the same diet? Excep
tion ? Why ? Too rich diet ? Horses ?

08 FOOD AXI) DRINK.

that too rich diet is injurious, just as truly as one that i«
inadequate. When the food of horses is too nutritious, in-
stinct leads them to gnaw the wood-work of their mangers.

12. Different Articles of Diet— Milk.— Milk is
the earliest nutriment of the human race, and in the selec-
tion and arrangement of its constituents, may be regarded
as a model food, no other single article being capable of
sustaining life so long. Cow's milk holds casein, one of
the albuminoids, about five parts in one hundred; a fatty
principle, when separated, known as butter, about four
parts; sugar of milk four parts; water and salts eighty-
seven parts. The casein and fatty substance are far more
digestible in milk, than after they have been separated
from it in the form of cheese and butter.

13. Since milk, in itself, is so rich an article of food,
the use of it as a beverage is unwise, unless the quantity
of the other articles consumed be reduced at the same
time. The milk sold in cities is apt to be diluted with
water. The way to detect the cheat is by testing the
specific gravity of the article. Good milk is about 1030;
ckimmed milk 1035; but milk diluted one-fifth is 1024.
An instrument called the lactometer is also used, by
which the amount of cream present is ascertained.

14. Eggs. — The egg is about two-thirds water, the bal-
ance is pure albumen and fat in nearly equal proportions.
The fat is in the yolk, and gives it its yellow color, l^gg-s
contain none of the sugar-principles, and should be eaten
with bread or vegetables that contain them. Soft-boiled
eggs are more wholesome than those which are hard-boiled
or fried, as the latter require longer time to digest.

15. Meats. — The meats, so called, are derived from the
muscular parts of various animals. They are most im-

1 2. Milk as a model food ? Cow's milk ? The constituents when separated y
1 3. Milk as a beverage ? Milk sold in cities ? How to detect the cheat ?
14. Composition of eggs? Yolk? How should eggs be eaten ? Why? How
t-oiled ? Why ?
1 5. Meats, whence derived ? Why important ? Fk-h of youuir animal- y

FOOD AND DRINK. 69

portant articles of food for adults, inasmuch as they are
richly stored with albuminoid substances, and contain
more or less fat. Such food is very nourishing and easily
digested if eaten when fresh, — veal and pork being excep-
tions. The flesh of young animals is more tender and, in
general, more digestible than that of older ones. All meat
is more tough immediately after the killing of the animal,
but improves by being kept a certain length of time.

16. Some persons prefer flesh that has begun to show
signs of decomposition, or is unmistakably putrid. By
some, venison is not considered to have its proper flavor
until it is tainted. In England, people prefer mutton
that is in a similar condition, just as on the continent of
Europe many delight in cheese that is in a state of decom-
position. In certain less civilized countries flesh is riot only
eaten uncooked, but in a mouldy, rotten condition. The
use of such food is not always immediately injurious, but
it predisposes to certain diseases, as indigestion and fevers.

17. Cold is one means of preserving meat from decay.
In the markets of northern Russia, the frozen carcases of
animals stand exposed for sale in the winter air for a con-
siderable time, and are sawn in pieces, like sticks of wood,
as the purchases are made; such meat, when thawed,
being entirely fit for food. Beef and pork are preserved
by salting down in brine, and in this condition may be
carried on long voyages or kept for future use. Salted
meat is not as nutritious as fresh, since the brine absorbs
its rich juices and hardens its fibres. Long continued use
of salt meats, without fresh vegetables, gives rise to the
disease called scurvy, formerly very prevalent on ship-
board and in prisons ; but now scarcely known.

18. Cooking. — The preparation of food by the agency

16. Preference of persons? Venison ? Mutton ? Cheese ? Uncooked flesh

17. Cold as a preserver ? Meat in Russia? Beef and pork, how preserved
Salted meat as food ? Scurvy *

18. The antiquity of the custom of cooking food? Object of cooking? Th
oyster ? Raw meat as an occasional food ?

70 FOOD AND DRINK.

of fire is of almost universal practice, even among the
rudest, 'nations... --.The- object of cooking is to render food
more easy —o^ Digestion by softening it, to develop its
flavor, aiid io^faise its temperature more nearly to that of
the body. A few articles of flesh-food are eaten un-
cooked in civilized lands, the oyster being an instance.
Raw meat is occasionally eaten by invalids with weak
digestive powers, and by men training for athletic con-
tests.

19. In boiling meat, the water in which it is placed
tends to dissolve its nutrient juices. In fact, the cooking
may be so conducted as to rob the meat of its nourish-
ment, its tenderness, and even of its flavor. The proper
method, in order to preserve or promote these qualities, is
to place the meat in boiling water, which, after a few
minutes, should be reduced in temperature. In this way
the intense heat, at first, coagulates the exterior layers of
albumen, and imprisons the delicate juices ; after that,
moderate heat best softens it throughout. When soup is
to be made, an opposite course should be pursued ; for
then the object is to extract the juices and reject the fibre.
Meat, for such purpose, should be cut in small pieces and
put into cold water, which should then be gradually raised
to boiling heat.

20. Roasting is probably the best method of cooking
meat, especially "joints" or large pieces, as by this process
the meat is cooked in its ow/i juices. Roasting should
begin with intense heat, and be continued at a moderate
temperature, in order to prevent the drying out of the
nutritious juices, as by this process an outer coating or
crust of coagulated albumen is formed. During this pro-
cess the meat loses one-fourth of its weight, but the loss
is almost wholly water, evaporated by the heat. Too

19. Effect of boiling meat? How may the cooking be done? The proper
method ? Effect ? Making of soup ?

20. Roasting? How should it be done? Give th.5 philo^phy of the proce>s.
Frying ?

FOOD AND

intense or prolonged heat will
Frying is the worst possible meth<
penetrating the meat, or other articli?
and hardens it, and thus renders it indigt

21. Trichina. — It should be remembered that ham,
sausages, and other forms of pork, should never be eaten
in a raw or imperfectly cooked condition. The muscle of
the pig is often infested by a minute animal parasite, or
worm, called trichina spiralis. This worm may be intro-
duced alive into the human body in pork food, where it
multiplies with great rapidity, and gives rise to a painful
and serious disease. This disease has been prevalent in
Germany, and cases of it occur from time to time in this
country.

22. Fish. — The part of fish that is eaten is the muscle,
just as in the case of the meats and poultry. It closely
resembles flesh in its composition, but is more watery.
Some varieties are very easy of digestion, such as salmon,
trout, and cod: others are quite indigestible, especially
lobsters, clams, and shell-fish generally. A diet in which
fish enters as the chief article, is ill adapted to strengthen
mind or body, while its continued use is said to be the
fertile source of nearly every form of disease of the skin.
Some persons are so constituted that they can eat no kind
of fish without experiencing unpleasant results.

23. Vegetable Food. — The list of vegetable articles
of diet is a very long one, including the grains from which
our bread-stuffs are made, the vegetables from the garden,
and the fruits. All the products of the vegetable king-
dom are not alike useful. Some are positively hurtful;
indeed, the most virulent poisons, as strychnia and prussic
acid, are obtained from certain vegetables. Again, of such

21 . What is " Trichina ?" How guarded against ?

22. What part of fish is eaten? What does it resemble? Fish as food for
digestion ? Fish as a diet ?

23. List of vegetable articles? Usefulness of the different vegetables?
Strychnia ? What further is said in relation to the nourishing and other qualities
of vegetables ?

72 FOOD AND DRINK.

articles as have been found good for food, some are more
nourishing than others: some require very little prepara-
tion for use, while others are hard and indigestible, and
can only be used after undergoing many preparatory pro-
cesses. Great care must therefore be exercised, and many
experiments made, before we can arrive at a complete
knowledge in reference to these articles of diet. Tea,
coffee, and other substances from which drinks are made,
ire of vegetable origin.

24. Bread. — Wheat is the principal and most valuable
kind of grain for the service of man. Bread made from
wheat-flour has been in use for many hundreds of years,
and on this account, as well as because of its highly
nourishing properties, has been aptly called " the staff of
life." We never become tired of good bread as an article
of daily food.

The white kinds of flour contain more starch and less
gluten than the darker, and are therefore less nutritious.
The hard-grain wheat yields the best flour. In grinding
wheat, the chaff or bran is separated by a process called
"bolting." Unbolted flour is used for making brown or
Graham bread.

25. The form of bread most easily digested is that which
has been " leavened," or rendered porous by the use of
yeast, or by some similar method. Unleavened bread
requires much more mastication. Hot bread is unwhole-
some, because it is not firm enough to be thoroughly mas-
ticated, but is converted into a pasty, heavy mass that is
not easily digested.

26. Wheaten bread contains nearly every principle requi-
site for sustaining life, except fat. This is commonly added
in other articles of diet, especially in butter, — " bread and
butter," consequently, forming an almost perfect article of

24. Wheat? " Staff of life ?" White flour? Hard-grain wheats ? Bolting?
Graham bread ?

25. Leavened bread? Unleavened? Hot bread ?

26. Wheaten bread ? Bread and butter ? Experiment on the dog ?

FOOD AND DRINK. 73

food. The following experiment is recorded : " A dog
eating ad libitum of white bread, made of pure wheat, and
freely supplied with water, did not live beyond fifty days.
He died at the end of that time with all the signs of
gradual exhaustion." Death took place, not because there
was anything hurtful in the bread, but because of the
absence of one or more of the food-principles.

27. The Potato. — The common or Irish potato is the
vegetable most extensively used in this country and Great
Britain. Among the poorer classes in Ireland it is the
main article of food. While it is not so rich in nutritious
substances as many others, it has some very useful qualities.
It keeps well from season to season, and men do not weary
of its continuous use. It is more than two-thirds water,
the balance being chiefly starch, with a little albumen.

28. The sweet potato differs from the white or common,
in containing more water and a small proportion of sugar.
The common potato and the tomato belong to the same
botanical order as the "nightshades," but do not possess
their poisonous qualities, unless we except potatoes that
are in the process of germination or sprouting, when they
are found injurious as food.

29. Fruits. — These are produced, in this country, in
great abundance, and are remarkable alike for their variety
and delicious flavor ; consequently they are consumed in
large quantities, especially during the warmer months.
The moderate use of ripe fruits, in their season, is
beneficial, because they offer a pleasant substitute for the
more concentrated diet that is used in cold weather. The
amount of solid nutriment they contain is, however,
small. The percentage of water in cherries is seventy-
five, in grapes eighty-one, in apples eighty two. Unripe
fruits contain starch, which, during the process of ripening,

27. State what is said of the Irish potato ?

28. Sweet potato ? Nightshades ? Potatoes when germinating?

29. Fruits? Use of ripe fruit? Nutriment they contain? Starch in unripe
fruits ? Cooking of unripe fruits ?

4

74 FOOD AND DRINK.

is converted into sugar. Such fruits are indigestible and
should be avoided : cooking, however, in part removes the
objections to them.

30. Pure Water. — It is important that the water we
drink and use in the preparation of food should be pure.
It should be clear and colorless, with little or no taste or
smell, and free from any great amount of foreign ingre-
dients. Chemically pure water does not occur in nature :
it is only obtained by the condensation of steam, carefully
conducted, and is not as agreeable for drinking purposes
as the water furnished by springs and streams. Rain-water
is the purest occurring in nature ; but even this contains
certain impurities, especially the portion which falls in the
early part of a shower; for in its descent from the clouds,
the particles floating in the air are caught by the falling
drops.

31. Water from springs and wells always contains more
or less foreign matter of mineral origin. This imparts to
the drink its pleasant taste — the sparkle, or " life," coming
from the gases absorbed by the water during its passage
under ground. The ordinary supply of cities is from some
pure stream or pond conveyed from a distance through
pipes, the limpid fluid containing generally only a small
amount of impurity. Croton water, the supply of New
York City, is very pure, and contains only four and a half
grains to a gallon : the Ridgewood water of Brooklyn holds
even less foreign matter.

32. Drinking- water may contain as large a proportion as
sixty to seventy grains per gallon of impurity, but a much
larger quantity renders it unwholesome. The mineral
spring waters, used popularly as medicines, are highly
charged with mineral substances. Some of them, such as

30. How should drinking-water be as regard? color and smell? Chemically
pure water ? How obtained ? Agreeablenes-s of perfectly pure water ?

31. Spring and well water? Whence the sparkle, or life? The water supply
of cities ? Croton wate ? Ridgewood ?

32. Impurities in drinking-water? Mineral springs ?

FOOD AND DRINK. 75

the waters at Saratoga, contain three hundred grains and
more to the gallon.

33. Action of Water upon Lead. — The danger of
using water that has been in contact with certain metals is
well known. Lead is one of the most readily soluble, and
probably the most poisonous of these substances in common
use. When pure water and an untarnished surface of lead
come in contact, the water gradually corrodes the metal,
and soon holds an appreciable quantity of it in solution.
When this takes place the water becomes highly injurious:
the purer the water, and the more recent the use of the
metal, the greater will be the danger.

34. In cities, lead pipes are commonly used to convey
water through the houses ; lead being also used in the con-
struction of roofs, cisterns, and vessels for keeping water
and other liquids. After the articles of lead have been in
use several months, the danger of lead-poisoning dimin-
ishes. An insoluble coating of the sulphate of lead forms
upon the exposed surface, thus protecting it from further
corrosion. It is, however, a wise precaution, at all times to
reject the water or other fluid that has been in contact
with leaden vessels over night, or for a number of hours.
Allow the water in pipes to run freely before using.

35. Coffee. — This is an important addition to diet, and
if moderately used is beneficial to persons of adult age.
As commonly employed, it consists of an infusion in boil-
ing water of the roasted and ground berry. The water
extracts certain flavoring and coloring matters, but that
which gives it its peculiar stimulant qualities is the alka-
loid caffein. With most persons its action is that of a
gentle stimulant, without any injurious reaction. It pro-
duces a restful feeling after exhausting efforts of mind or

33. What is stated of the action of water upon lead ?

34. Lead in pipes and other things ? Advice ? What takes place after the arti,
cles of lead have been used much ? What is wise ?

35. Coffee as an article of diet? Of what does it consist? How does the
water affect the coffee? The peculiar stimulant ? How does it affect most per

7(? FOOD AND DRINK.

body; it tranquilizes, but does not disqualify for labor;
and hence it is highly esteemed by persons of literary pur-
suits.

36. Another property of coffee is, that it diminishes the
waste of the tissues, and consequently permits the per-
formance of excessive labor upon an economical and in-
adequate diet. This has been tested among the miners of
Belgium. Their allowance of solid food was below that
found necessary in prisons and elsewhere; but, with the
addition of about four pints of coffee daily, they were en-
abled to undergo severe labor without reducing their mus-
cular strength. The caravans which traverse the deserts
are supported by coffee during long journeys and length-
ened privation of food. Among armies it is indispensable
in supplementing their imperfect rations, and in relieving
the sense of fatigue after great exposure and long marches.
When taken with meals, coffee is also thought to promote
digestion.

37. Tea. — The effects of tea-drinking are very similar
to those of coffee, and are due to a peculiar principle called
thein. This principle is probably the same as that found
in coffee, caffein, since the chemical composition of both
is precisely alike. Tea, as a beverage, is made from the
dried leaves of the plant by the addition of hot water; if
the tea is boiled, the oil which gives it its agreeable flavor
is driven off with the steam. There are two kinds of
tea — the black and the green : the latter is sometimes in-
jurious, producing wakefulness and other nervous symp-
toms. The excessive use of either coffee or tea will cause
wakefulness.

38. During Dr. Kane's expedition in the Arctic regions,
the effects of these articles were compared. "After re-

36. Another property of coffee? Miners of Belgium? The Caravans?
A MI ong armies? Taken with meals?

37. Effects of tea-drinking? Peculiar principle? The tea beverage, how
made ? Black and green tea ? Excessive use of tea or coffee ?

38. Experiments made during Kane's expedition ?

FOOD AtfB DRINK. ' 77

peated trials, the men took most kindly to coffee in the
morning and tea in the evening. The coffee seemed to
continue its influence throughout the day, and they seemed
to grow hungry less rapidly than after drinking tea, while
tea soothed them after a day's hard labor, and the better
enabled them to sleep. They both operated upon fatigued
men like a charm, and their superiority over alcoholic
stimulants was very decided."

39. Chocolate is made from the seeds of the cocoa-tree,
a native of tropical America. Its effects resemble some-
what those of tea and coffee, but it is very rich in nutri-
ment. Linnaeus, the botanist, was so fond of this beverage,
that he gave to the cocoa-tree the name, Theobrovia — " the
Food of the Gods." Its active principle is theobromin.

40. Alcohol. — The list of beverages that are consumed
for the sake of the alcohol they contain is a very long one.
Their use is almost universally prevalent, every civilized
nation, and nearly every barbarous one, having its favorite
alcoholic drink ; and, as a general rule, the nations which
stand the highest in civilization have the greatest varieties
of these beverages, — at the same time using them the most
intelligently and wisely.

41. The wines and malt liquors that contain a small
amount of alcohol are produced by fermentation. The
beverages that hold a large proportion of alcohol, the
" ardent spirits," are made by distillation. Enormous
quantities of grains and fruits are thus yearly diverted
from their proper uses as food ; some of these being corn,
wheat, rye, barley, potatoes, and rice ; also the grape, apple,
pear, peach, sugar-cane, cherry, fig, and orange. Wine, the
fermented juice of the grape, has been in use from time
immemorial, while the introduction of distilled liquors
dates from a comparatively recent period.

39. State what is said of chocolate.

40. Use of alcoholic drink:?, how general "> The rule given 1

41 . The beverages produced by fermentation ? The ardent spirits '! Grains and
fruits employed ? Long use of wine ? Of distilled liquors ?

78 FOOD ANJ) JJULNK.

42. What is the physiological action of alcohol ? Its first
and most evident action is stimulation : this effect is tran-
sient, and is followed by a variable degree of depression.
At first it sharpens the appetite and quickens digestion,
but its habitual use impairs both. This stimulation is
efficient in giving the system an artificial strength during
some temporary derangement, and in enabling the endur-
ance of unusual fatigue or exposure. The experience of
Dr. Hayes, and other explorers of the polar regions, is that
alcohol does not enable the body to resist the influence of
cold, but, on the contrary, is always injurious.

43. Another property it has in common with tea and
coffee. It supports the powers of life, economizes food, and
retards the waste of tissues ; in other words, it " banks the
fires," and prevents their burning wastefully. On this
principle we explain the restorative influence of wines or
liquors during exhausting diseases, in convalescence, and
after excessive labors of mind or body.

44. Pure alcohol, or an excessive quantity of ardent
spirits, is an undoubted poison, and has been frequently
known to produce fatal results. Stimulants in moderate
quantities have been thought to increase strength, and in
this view they have been called "alcoholic foods." This is
not now conceded by scientific men. The prevailing opin-
ion is, that they serve no useful purpose as an article of
diet, and that their beneficial influence is limited to cases
where the system is enfeebled, where some unnatural de-
mand is made upon the vital powers, or where the supply
of food is insufficient. Hence, while alcohol has not the
power to build up, it may obstruct the process of pulling
down.

42. Describe the aciton of alcohol upon the human system? Experience of
Dr. Hayes and others ?

43. Another property of alcohol ? How do we explain the restorative influence
of wines and liquors ?

44. Alcohol, a poison? Moderate stimulants ? Prevailing opinion ? Hence?

REVIEW QUESTIONS. 79

QUESTIONS FOE TOPICAL KEVIEW.

PAGE

1. How is the necessity for food shown ? ^4

2. To what process of waste and repair is the body constantly subjected ? 64

3. How do you account for the sensations of hunger and thirst ? 05

4. What further can you state having relation to the subject ? .65

5. What can you state in regard to the quantity of food required for the

support of life ? ^ 66

6. What circumstances change the needs of persons, old and yonng, as re-

gards food and drink? "' 65 67

7. What becomes of all the food and drink we consume ? ' gg

8. What further can you state in relation to the process of renovation through

. which the body passes ? gg

9. What can you state of the habits of nations in respect to diet ? 66, 67, 69

10. What in relation to the selection of articles for food ? 67

11. What as respects the necessity for changing or varying the diet ? 67

12. What has been proved as regards animal food ? 67

13. Of what importance is milk as an article of food ? 67, 68

14. What are the constituents of milk ? 68

15. What can you state of eggs as an article of food ? 68

16. Of the meats, so called, as an article of food ? 68, 6!)

17. What effect does cold have upon meats ? 69

18. In what other way may beef and pork be preserved ? <j9

19. What can you state of salted meat as food, and of its continued use ? 59

20. What change does meat undergo in the cooking ? 70, 71

21. What directions are given for boiling meat ? 70

22. What for roasting, and with what results ? 70, 71

23. What is said about the frying of meats ? 71

24. Give the statement in relation to trichina 71

25. State what is said in relation to fish 71

26. What is stated of the usefulness and other properties of the products of

the vegetable kingdom ? 71, 72

27. What further is said of vegetable food ? 71, 72

28. Why is bread made of wheat flour so important as an article of food ? 72

29. State whatever else you can in relation to bread 72, 73

30. Give the statement respecting the potato 73

31. What is stated of fruits, the use of them, their nutritious qualities, etc.? 73, 74

32. How general is the existence of perfectly pure water ? 74

33. What is stated in relation to drinking water ? 74, 75

34. How does the action of water upon lead affect lead ? 75

35. What further can you state on the subject ? 75

36. What properties has coffee as an article of diet ? 75. 76

37. In what circumstances has coffee been found peculiarly beneficial ? 76

38. What comparison is made between coffee, tea, and chocolate ? 76

39. How are the wines, and malt and other alcoholic beverages produced ? 77

40. What articles are employed in their production ? 77

41. Describe the physiological action of alcohol 78

42. What comparison is made between tea, coffee, and alcohol ? 78

43. What can you state of alcohol, as a poison, a stimulant, and article of diet ? 78

44. What, then, can be said of alcohol as a recommendation ? 73

80 DIGESTION.

CHAPTER VI.
DIGESTION.

TJw Principal Processes of Nutrition — The General Plan of Digestion
—Mastication — Tlie Teeth — Preservation of the Teeth — Insalivation
— The Stomach and tlte Gastric Juice — The Movements of tlie
Stomach — Gastric Digestion — The Intestines — TJie Bile and Pan-
creatic Juice — Intestinal Digestion — Absorption by means of Blood-
vessels and Lacteals — Tlie Lymphatic or Absorbent System — The
Lymph — Conditions which affect Digestion — The Quality, Quan-
tity, and Temperature of Hie Food — The Influence of Exercise and
Sleep.

1. Nutrition. — The great design of food is to give
nutriments nourishment to the body. But this is not
accomplished directly, as the food must first pass through
certain preparatory changes, as follows : (1), Digestion, by
which the food is reduced to a soluble condition; (2), Ab-
sorption, by which, when digested, it is imbibed into the
blood; (3), Circulation, which carries the enriched blood
to the various parts of the system; and (4), Assimilation.
by which each tissue derives from the blood the materials
necessary for its support.

2. By these means the sustaining power of food is grad-
ually developed and employed, and the vital machinery
kept in working order, somewhat after the manner of the
steam-engine. To operate the latter, the force imprisoned
within the coal and water is set free and converted into
motion by the combustion of the fuel and the vaporization
of the water. It will be seen, however, when we come to
study these operations in the human body, that they are
conducted silently and harmoniously, with marvellous deli-
cacy and completeness, and without that friction, and con-

1 . Design of food ? How accomplished ?

2. Sustaining power of food ? Simile of the engine ? Operation in the human
body ?

DIGESTION.

81

sequent loss of power, which attend the working of the
most perfect machinery of man's invention.

3. General Plan of Digestion. — The great change
which food undergoes in digestion is essentially a reform-
ing process, reducing articles of

diet, which are at first more or
less solid, crude, and coarse, to
a liquid and finely comminuted
condition, suitable for absorption
into the blood. The entire pro-
cess of digestion takes place in
what is called the alimentary
canal, a narrow, tortuous tube,
about thirty feet in its entire
length. This canal begins in
the mouth, extends thence down-
ward through the gullet to the
stomach (a receptacle in which
the principal work of digestion
is performed), and thence onward
through the small and large in-
testines'.

4. The stomach and intestines
are situated in the cavity of the

attfomen (Fig. 16, C, and Fig. 22), FlG 16._SECTION op THE TRUNK

and OCCUpy about two-thirds of SHOWING THE CAVITIES OP THE
. , rf., , . . . , ., CHEST AND ABDOMEN.

its space. The action to which the A< CaVit,y of chest ;
food is subjected in these organs c' Abffi5?;
is of two kinds— mechanical and D* E' Spinal bolumn-
chemical. By the former it is crushed, agitated, and car-
ried onward from one point to another; by the latter it is
changed in form through the solvent power of the various
digestive juices.

3. Change of food in digestion? Process of digestion? Describe the alimen-
tary canal.

4. Situation of the stomach and intestines ? Action of the food ? Mechanical
action ? Chemical ?

4*

DIGESTIOX.

5. Mastication. — As soon as solid food is taken into
the mouth, it undergoes mastication, or chewing. It is
caught between the opposite surfaces of the teeth, and by
them is cut and crushed into very small fragments. In

the movements of chewing,
the lower jaw plays the chief
part; the upper jaw, having
almost no motion, acts sim-
ply as a point of resistance,
to meet the action of the
former. These movements
of the lower jaw are of three
sorts: a vertical or cutting,
a lateral or grinding, and a
to-and-fro or gnawing mo-
tion.

6. The teeth are composed
of a bone-like material, and
are held in place by roots
running deeply into the jaw.
exposed portion, or
is protected by a
thin layer of enamel (Fig.
17, «), the hardest substance
in the body, and, like flint, is capable of striking fire with
steel. In the interior of each tooth is a cavity, containing
blood-vessels and a nerve, which enter it through a minute
opening at the point of the root (Fig. 19).

7. There are two sets of teeth ; first, those belonging to
the earlier years of childhood, called the milk teeth, which
are twenty in number and small. At six or eight years of
age, when the jaw expands, and when the growing body
requires a more powerful and numerous set, the roots of

PIG. 17.— SECTION OF A TOOTH.

a, Enamel; b. Cavity- cc, Roots:

d, Body of the Tooth.

The

" crown,"

5. Describe the process of mastication ? How many and what movements ?

6. Composition of the teeth ? Enamel of the teeth ? Interior of teeth *

7. The milk teeth ? The permanent teeth ?

DIGESTION.

83

the milk teeth are absorbed, and the latter are "shed." or
fall out, one after another (Fig. 18), to make room for the
permanent set.

PIG. 18.— SECTION OF THE JAWS.
1' 2' 3' 4 5'. The Milk Teeth ; 1" to 8", The Germs of the Permanent Set.

8. There are thirty-two teeth in the permanent set, as
many being in one jaw as the other. Each half-jaw has
eight teeth, similarly shaped and arranged in the same
order : thus, two incisors, one canine, two bicuspids, and
three molars. The front teeth are small, sharp, and chisel-
edged, and are well adapted for cutting purposes; hence
their name incisors. The canines stand next, one on each
side of the jaw; these receive their name from their resem-
blance to the long, pointed tusks of the dog (Fig. 19).

8,9. Number of teeth ? How distributed ?

84

DIGESTION.

9. The bicuspids, next in order, are larger and have a
broader crown than the former; while behind them are
the molars, the largest and most powerful of the entire set.
These large back teeth, or " grinders," present a broad,
rough surface, suitable for holding and crushing the food.

FIG. 19.— SECTION op THE JAWS— RIGHT SIDE.

V, A, N. Veins. Arteries, and Nerves of the Teeth. The root of one tooth in each
jaw is cut vertically to show the cavity and the blood-vessels, etc., \\ithm H.
1 to 8, Permanent Teeth.

The third molar, or " wisdom tooth," is the last to be cut,
and does not appear until about the twenty-first year.

DIGESTION. 85

The order of arrangement of the teeth is indicated by the
following dental formula: —

M- "s~~ -M
B''' ~XB

c/4\c
I

10. It is interesting, at this point, to notice the different
forms of teeth in different animals, and observe how ad-
mirably their teeth are suited to the respective kinds of
food upon which they subsist. In the carnivora, or flesh-
feeders, the teeth are sharp and pointed, enabling them
both to seize their prey, and tear it in pieces ; while the
herbivora, or vegetable- feeders, have broad, blunt teeth,
with rough crowns, suitable for grinding the tough grasses
and grains upon which they feed. Human teeth partake
of both forms ; some of them are sharp, and others are
blunt ; they are therefore well adapted for the mastication
of both flesh and vegetables. Hence we argue that,
although man may live exclusively upon either vegetable
or animal food, he should, when possible, choose a diet
made up of both varieties.

11. Preservation of the Teeth. — In order that the
teeth shall remain in a sound and serviceable condition,
some care is of course requisite. In the first place, they
require frequent cleansing ; for every time we take food,
some particles of it remain in the mouth ; and these, on
account of the heat and moisture present, soon begin to
putrefy. This not only renders the breath very offensive,
but promotes decay of the teeth.

10. Different forms of teeth ? Human teeth ? The inference ?

1 1 . Cleaning of teeth ? Effects of not cleaning ?

SG DIGESTION.

12. The saliva, or moisture of the mouth, undergoes a
putrefactive change, and becomes the fertile soil in which
a certain minute fungus has its growth. This fluid, too, if
allowed to dry in the mouth, collects upon the teeth in the
form of an unsightly, yellow concretion, called tartar.
To prevent this formation, and to remove other offensive
substances, the teeth should be frequently cleaned with
water, applied by means of a soft tooth-brush. The de-
struction of the tartar fungus is best effected by the use
of a weak solution of carbolic acid.

13. Again, it should be borne in mind that the enamel,
Nature's protection for the teeth, when once destroyed, is
not formed anew ; and the body of the tooth thus exposed,
is liable to rapid decay. On this account, certain articles
are to be guarded against ; such as sharply acid substances
that corrode the enamel, and hard substances that break
or scratch it — as gritty tooth powders, metal tooth picks,
and the shells of hard nuts. Sudden alternations from
heat to cold, when eating or drinking, also tend to crack
the enamel.

14. Insalivation. — When the morsel of food is* cut and
ground by the teeth, it is at the same time also intimately
mixed with the saliva, or fluids of the mouth. This con-
stitutes the second step of digestion, and is called insaliva-
tion. The saliva, the first of the digestive solvents, is a
colorless, watery, and frothy fluid. It is secreted (i. e.
separated from the blood) partly by the mucous mem-
brane which lines the mouth ; but chiefly by the salivary
glands, of which there are three pairs situated near the
mouth.

15. These glands consist of clusters of very small

12. Effects upon the saliva? Formation of tartar? How prevented? How
destroyed ?

13. Destruction of the enamel * How enarded against?

1 4. Mixing of food with the saliva V What is the' saliva ? How secreted ? The
salivary glands?

1 5. The flow of saliva ? The thought of food ? Anxiety and grief? Animals
fed upon dry and coarse food ?

DIGESTION.

pouches, around which a delicate network of blood-vessels
is arranged: they empty into the mouth by means of
little tubes, or
ducts. The flow
from these glands
is at all times suf-
n'cient to maintain
a soft and moist
condition of the
tongue and mouth;
but when they are
excited by the pres-
ence and taste of
food, they pour

forth the Saliva FlG- 20-— STRUCTURE OP A SALIVARY GLAND.

more freely. Even the mere thought of food will at
times cause the saliva to flow, as when the appetite is
stimulated by the sight or smell of some savory article ; so
that the common expres-
sion is correct that " the
mouth waters" for the fa-
vorite articles of food.
Anxiety and grief prevent
its flow, and cause "the
tongue to cleave to the
roof of the mouth." In
the horse and other ani-
mals, that feed upon dry
and coarse fodder, and re-

-i -t FIG. 21.— THE HEAD OP A HORSE, showing the

quire an abundant SUp- large salivary gknd (a), its duct (6), the

ply of saliva, we find large

salivary glands, as well as powerful muscles of mastication.

16. The mingling of the saliva with the food seems a

simple process, but it is one that plays an important part

1 6. Importance of the process ? The first place ? The second ? The third ?

88 DIGESTION.

in digegtion. In the first place, it facilitates the motions
of mastication, by moistening the food and lubricating the
various organs of the mouth. Secondly, it prepares the
way for other digestive acts: by the action of the teeth,
the saliva is forced into the solid food, softens the harder
substances, and assists in converting the whole morsel into
a semi-solid, pulpy mass, that can be easily swallowed, and
readily permeated by other digestive fluids. The saliva
also, by dissolving certain substances, as sugar and salt,
develops the peculiar taste of each ; whereas, if the tongue
be dry and coated, they are tasteless. Hence, if substances
are insoluble, they are devoid of taste.

17. Finally, the saliva has the property of acting chemi-
cally upon the food. As we have before stated (Chap. IV.),
starch, as starch, cannot enter the tissues of the body ; but,
in order to become nutriment, must first be changed to
grape sugar. This change is, in part, effected by the saliva,
and takes place almost instantly, whenever it comes in con-
tact with cooked starch. This important function is due
to an organic ingredient of the saliva • called ptyalin.
This substance has been extracted from the saliva by
the chemist, and has been found, by experiment, to
convert into sugar two thousand times its own weight of
starch.

18. Importance of Mastication and Insaliva-
tion. — Each of these processes complements the other,
and makes the entire work available; for, by their joint
action, they prepare the food in the best possible manner
for further digestive changes. The knowledge of these
preliminary functions will appear the more important,
when we reflect that they are the only ones which we can
regulate by the will. For, as soon as the act of swallowing
begins, the food not only passes out of sight, but beyond

IT. Its final importance ? Starch ? How effected ? Ptyalin ?
18. Each of the processes? Why is a knowledge of the digestive function
important ? How shown ?

DIGESTION. 89

control ; and the subsequent acts of digestion are conse-
quently involuntary and unconsciously performed.

19. It is generally known that rapid eating interferes
with digestion. How does this occur ? In the first place,
in rapid eating, the flow of the saliva is insufficient to
moisten the solid parts of the food, so that they remain too
hard and dry to be easily swallowed. This leads to the
free and frequent use of water, or some other beverage, at
meals, to " wash down" the food, — a most pernicious prac-
tice. For these fluids, not only cannot take the place of
the natural digestive juices, but, on the contrary, dilute
and weaken them.

20. Secondly, the saliva being largely the medium of the
sense of taste, the natural flavors of the food are not devel-
oped, and consequently it appears comparatively insipid.
Hence the desire for high-seasoned food, and pungent
sauces, that both deprave the taste and over excite the
digestive organs. Rapid eating also permits the entrance
of injurious substances which may escape detection by the
taste, and be unconsciously received into the system. In
some instances, the most acrid and poisonous substances
have frequently been swallowed " by mistake," before the
sense of taste could act, and demand their rejection.

21. Thirdly, the food, being imperfectly broken up by
the teeth, is hurried onward to the stomach, to be by it
more thoroughly divided. But the task thus imposed upon
the stomach, it is not at all adapted to perform ; so that the
crude masses of food remain a heavy burden within the
stomach, and a source of distress to that organ, retarding
the performance of its legitimate duty. Hence persons
who habitually eat too rapidly, frequently fall victims to
dyspepsia. Rapid eating also conduces to overeating.
The food is introduced so rapidly, that the system has not

19. Rapid eating? Describe the process and effects.

20. Loss of taste? Another effect of rapid eating? Mistakes?

21. Effect of imperfectly broken food in the stomach * Dyspepsia? Over-
eating ?

DIGESTION.

time to recognize that its real wants are met, and that its
losses have been made good; and hence the appetite con-
tinues, although more nutriment has been swallowed than
the system requires, or can healthfully appropriate.

22. The Stomach. — As soon as each separate portion
of food is masticated and insalivated, it is swallowed ; that

is, it is propelled down-
ward to the stomach,
through a narrow mus-
cular tube about nine
inches in length, called
the ffisopliagux, or gul-
let (Fig. 'S3). The
stomach is the. only
large expansion of the
digestive canals and is
the most important or-
gan of digestion. It is
a hollow, pear-shaped
pouch, having a ca-
pacity of three pints,
in the adult. Its walls
are thin and yielding,
and may become un-
naturally distended, as
in the case of those
who subsist on a bul-
ky, innutritions diet,
and of those who habitually gormandize.

23. The stomach has also two openings; that by which
food enters, being situated near the heart, is called the
cardiac, or heart orifice; the other is the pylorus, or
" gatekeeper," which guards the entrance to the intestines,

. 22. — SECTION op CHEST AND ABDOMEN.

A, Heart. D, The Liver.

B, The Lungs. E, Large Intestine.

C, Stomach. G, Small Intestine.

22. Gullet? Describe the stomach and its location. Effects of gormandizins?

23. Heart-orifice? Gatekeeper? Coins, etc.? Indication of the soil and
yielding texture of the stomach ?

DIGESTION.

91

-c

and, under ordinary circumstances, permits only such

matters to pass it as have first been properly acted upon

in the stomach. Coins, buttons, and the like are, however.

readily allowed to pass, because they can be of no use if

retained. The soft and

yielding texture of this

organ — the stomach —

indicates that it is r^h

designed to crush antT

comminute solid articles

of food.

24. The Gastric0
Juice.— We have seen
how the presence of food
in the mouth excites the
salivary glands, causing
the saliva quickly to
flow. In the same man-
ner, when food reaches
the stomach, its inner
lining, the mucous mem-
brane, is at once excited
to activity. (At first its
surface, which while the
stomach is empty pre-
sents a pale pink hue,
turns to a bright red
color, for the minute
blood-vessels which
course through it, are filled with blood. )( Presently a clear,
colorless, and acid fluid exudes, drop by drop, from its nu-
merous minute glands or "tubules," until finally the surface
is moistened in every part, and the fluid begins to mingle
with the food. This fluid is termed the gastric juice. \

FIG. 23.— THE ORGANS OF DIGESTION.

O, O3«ophagus. I, Small Intestines.
S, Stomach. C, Large Intestines.

L, Liver. P, Pancreas.

M, Pylorus. N, Spleen.

G, Gall-bladder.

24. What is meant by the gastric juice ?

92 DIGESTION.

25. The gastric juice is the proper solvent of certain
articles of food, especially those belonging to the albu-
minoid class. This solvent power is due to its peculiar in-
gredient, pepsin ; in digestion, this substance acts like a
ferment ; that is, it induces changes in the food simply by
its presence, but does not itself undergo change. The acid-
ity of the gastric juice, which is due to lactic acid, is not
accidental; for we find that the |flpi cannot act in an
alkaline solution — that is, one whicn is not acid or neutral.

fThe quantity of gastric juice secreted daily is very large,
probably not less than three or four pints at each meal.
Though this fluid is at once used in the reduction of the
food, it is not lost; since it is soon re-absorbed by the
stomach, together with those parts of the food which it
has digested and holds in solution. \

26. Movements of the Stomach. — The inner coat-
ing of the stomach is the mucous membrane, which, as we
have seen, furnishes the gastric juice. Next to this coating
lies another, called the muscular coat, composed of invol-*
untary muscular fibres, some of which run circularly, and
others in a longitudinal direction. These expand to ac-
commodate the food as it is introduced, and contract as it
passes out, In addition, these fibres are in continual mo-
tion while food remains in the stomach, and they act in
such manner that the contents are gently turned round
from side to side, or from one end of it to the other.

27. By these incessant movements of the stomach,
called the peristaltic movements, the gastric juice comes
in contact with all parts of the food. We are, however,
not conscious that these movements take place, nor have
we the power to control them. When such portions of the
food as are sufficiently digested approach the pylorus, it

25. .What is the office of the gastric juice? Acidity of the gastric juice*
Quantity of gastric juice used ? What becomes of it ?

26. Muscular coat of the stomach? Expansion and contraction of its fibres?
Action of the fibres?

27. Peristaltic movements? What is said of our consciousness of and power
over these movements ? Describe the movements of the pylorus.

DIGESTION. 93

expands to allow them to pass out, and it closes again to
confine the residue for further preparation.

28. The knowledge of these and other interesting and
instructive facts has been obtained by actual observation ;
the workings of the stomach of a living human being have
been laid open to view and examined — the result of a re-
markable accident. Alexis St. Martin, a Canadian voyageur,
received a gun-shot wound which laid open his stomach,
and which, in healing, left a permanent orifice nearly an
inch in diameter. Through this opening the observer
could watch the progress of digestion, and experiment with
different articles of food. Since that occurrence, artificial
openings into the stomach of the inferior animals have
been repeatedly made, so that the facts of stomach-digestion
are very well ascertained and verified.

29. Gastric Digestion. — What portions of the food
are digested in the stomach ? It was formerly thought
that all the great changes of digestion were wrought here,
but later investigation has taught us better. We now know
that the first change in digestion takes place in the mouth, in
the partial conversion of starch into sugar. We also know
that, of the three organic food principles (considered in
Chapter IV.) two — the fats and the sugars — are but slightly
affected by the stomach ; but that its action is confined to
that third and very important class, from which the tissues
are renewed, the albuminoids. A few articles need no
preparation before entering the system, as water, salt, and
grape-sugar. These are rapidly taken up by the blood-
vessels of the stomach, which everywhere underlie its
mucous membrane in an intricate and most delicate net-
work. In this way the function of absorption begins.

30. The albuminoid substances are speedily attacked and

28. How has the knowledge and the workings of the stomach been ascertained ?
St. Martin? How else?

29. What was formerly thought. ? What do we now know ? What else do we
now know ? Water, salt, and sugar? Absorption ?

30. Albuminose? The process ? Chyme?

94 DIGESTION.

digested by the gastric juice. From whatever source they
are derived, vegetable or animal, they are all transformed
into the same digestive product, called albuminose. This is
very soluble in water, and is readily absorbed by the blood-
vessels of the stomach. After a longer or shorter time,
varying from one to five hours, according to the individual
and the. quantity and quality of his food, the stomach will
be found empty. Xot only has the digested food passed
out, but also those substances which the stomach could
not digest or absorb have passed little by little through
the pylorus, to undergo further action in the intestines.
At the time of its exit, the digested food is of a pulpy
consistence, and dark color, and is then known as the chyme.

31. The Intestines. — The intestines, or "bowels,"'
are continuous with the stomach, and consist of a fleshy
tube, or canal, twenty-five feet in length. The small
intestine, whose diameter is about one inch and a half, is
twenty feet long and very tortuous. The large intestine is
much wider than the former, and five feet long (Fig. 2§).
The general structure of these organs resembles that of the
stomach. Like it, they are provided with a mucous mem-
brane, or inner lining, whence flow their digestive juices;
and, just outside of this, a muscular coat, which propels
the food onward from one point to another.

32. Moreover, both the intestines and stomach are envel-
oped in the folds of the same outer tunic or membrane, called
the peritoneum. This is so smooth and so well lubricated,
that the intestines have the utmost freedom of motion.
In the small intestines, the work of digestion is completed,
the large intestine receiving from them the indigestible
residue of the food, and in time expelling it from the body.

33. Intestinal Digestion. — As soon as the food
passes the pylorus and begins to accumulate in the upper

31. What are the intestines? The small intestines? The large intestines?
Their structure?

32. Peritoneum ? The work of digestion ?

33. The presence of food in the intestines ? ,Bile ?

DIGESTION. 95

part of the intestines, it excites the flow of a new digestive
fluid, which enters through a small tube, or duct, about
three inches below the stomach. It is formed by the union
of two distinct fluids — the bile and the pancreatic juice.
The bile is secreted by the liver, which is the largest gland
of the body, and is situated on the right side and upper
part of the abdomen (Fig. 22). The bile is constantly
formed, but it flows most rapidly during digestion. Dur-
ing the intervals of digestion it is stored in the gall-bladder ',
a small membranous bag attached to the under side of the
liver. This fluid is of a greenish-yellow color, having a
peculiar smell, and a very bitter taste.

34. The pancreatic juice is the product of a gland called
$\Q pancreas, situated behind the stomach. This fluid is col-
orless, viscid, and without odor. Like the digestive juices
previously described, it owes its solvent power to its pecu-
liar ferment principle, called pancreatin. By the joint
action of these fluids, the fatty parts of the food are pre-
pared for absorption. By previous steps of digestion the
fats are merely separated from the other components of the
food ; but here, within the intestines, they are reduced to a
state of minute division, or emulsion, resembling the con-
dition of butter in milk, before it has been churned.
There results from this action a white and milky fluid,
termed the chyle, which holds in solution the digestible
portions of the food, and is spread over the extensive
absorbent surface of the small intestines.

35. The mucous membrane of the intestines, also,
secretes or produces, a digestive fluid by means of numer-
ous "follicles," or minute glands; this is called the in-
testinal juice. From experiments on the inferior animals,
it has been ascertained that this fluid exerts a solvent influ-
ence over each of the three organic food principles, and in
tins' way may supplement and complete the action of the

34. The pancreatic juice ? The joint action of these fluids* ?

35. The mucous membrane ? Experiments on inferior animals ?

96 DIGESTION.

fluids previously mentioned, viz. : — of the saliva in convert-
ing starch into sugar, of the gastric juice in digesting the
albuminoids, and of the pancreatic juice and bile in
emulsifying the fats.

36. Absorption. — With the elaboration of the chyle,
the work of digestion is completed ; but, in a certain sense,
the food is yet outside of the body ; that is, the blood is not
yet enriched by it, and it is not in a position to nourish the
tissues. The process by which the liquefied food passes out
of the alimentary canal into the blood is called absorption.
This is accomplished in two ways ; first, by the blood-vessels.
We have seen how the inner membrane of the stomach is
underlaid by a tracery of minute and numerous vessels,
and how softie portions of the food are by them absorbed.
The supply of blood-vessels to the intestines is even
greater; particularly to the small intestines, where the
work of absorption is more actively carried on. /

37. The absorbing surface of the small intestines, if con-
sidered as a plane surface, amounts to not less than half a
square yard. Besides, the mucous membrane is formed in
folds with an immense number of thread-like prolongations,
called villi, which indefinitely multiply its absorbing capa-
city. These minute processes, the villi, give the surface
the appearance and smoothness of velvet; and during
digestion, they dip into the canal, and, by means of their
blood-vessels, absorb its fluid contents, just as the spongi-
oles which terminate the rootlets of plants, imbibe moisture
from the surrounding soil.

38. Secondly, absorption is also effected by the lacteals, a
set of vessels peculiar to the small intestines. These have
their beginnings in the little villi just mentioned, side by
side with the blood-vessels. These two sets of absorbents
run in different courses, but their destination is the same,

36, 37. How much thus far has been done with the food ? The next process ?
Give the first way.

38. How is absorption effected in another way? Describe it. Name of the
"teals ? Thoracic duct ?

DIGESTION.

97

which is the right side of the heart. The lacteals receive
their name from their milky-white appearance. After a
meal containing a por-
tion of fat, they are
then distended with
chyle, which they are
specially adapted to
receive: at other times
they are hardly dis-
cernible. The lacteals
all unite to form one
tube, the thoracic duct,
which passes upward
through the thorax, or
chest, and empties into
a large vein, situated
just beneath the left
collar-bone.

39. The Absorb-
ents, — The lacteals
belong to a class of

vessels known as absorbents, or lymphatics, which ram-
ify in nearly all parts of the body, except the brain and
spinal cord. The fluid which circulates through the lym-
phatics of the limbs, and all the organs not concerned in
digestion, is called lympli. This fluid is clear and color-
less, like water, and thus differs from the milky chyle
which the lacteals carry after digestion : it consists chiefly
of the watery part of the blood, which was not required by
the tissues, and is returned to the blood by the absorbents
or lymphatics.

40. Circumstances affecting Digestion. — What
length of time is required for the digestion of food ? From
observations made, in the case of St. Martin, the Canadian

FIG. 24. — THE LACTEALS.
A, Small Intestine. B, Lacteals.
C, Thoracic Duct. D, Absorbents.

E, Blood-vessel.

39. The absorbents ? Lymph ? What further of tho lymph ?

40. What can you state as to the time required for digestion ?

98 DIGESTION.

already referred to, it has been ascertained that, at the end
of two hours after a meal, the stomach is ordinarily empty.
How much time is needed to complete the digestion of
food, within the small intestines, is not certain ; but, from
what we have learned respecting their functions, it must
be evident that it largely depends upon the amount of
starch and fat which the food contains.

41. In addition to the preparations which the food
undergoes in cooking, which we have already considered,
many circumstances affect the duration of digestion ; such
as the quality, quantity, and temperature of the food ; the
condition of the mind and body ; sleep, exercise, and habit.
Fresh food, except new bread and the flesh of animals
recently slain, is more rapidly digested than that which is
stale ; and animal food more rapidly than that from the
vegetable kingdom.

42. Food should not be taken in too concentrated a form,
the action of the stomach being favored when it is some-
what bulky ; but a large quantity in the stomach often re-
tards digestion. If the white of one egg be given to a dog,
it will be digested in an hour, but if the white of eight
eggs be given it will not disappear in four hours. A wine-
glassful of ice-water causes the temperature of the stomach
to fall thirty degrees ; and it requires a half-hour before it
will recover its natural warmth — about a hundred degrees —
at which the operations of digestion are best conducted.
A variety of articles, if not too large in amount, is more
easily disposed of than a meal made of a single article;
although a single indigestible article may interfere with
the reduction of articles that are easily digested.

43. Strong emotion, whether of excitement or depression,
checks digestion, as do also a bad temper, anxiety, long
fasting, and bodily fatigue. The majority of these condi-

41. Circumstances affecting duration of digestion ? Fresh food ?

42. Food in concentrated form ? A large quantity of food? Experiment on
the dog ? Ice-water ? Variety of articles ?

43. Strong emotion ? The tongue of the patient ?

DIGESTION.

99

tions make tlie mouth dry, that is, they restrain the flow
of the saliva ; and without doubt they render the stomach
dry also, by preventing the flow of the gastric juice. And,
as a general rule, we may decide, from a parched and coated
tongue, that the condition of the stomach is not very dis-
similar, and that it is unfit for the performance of digestive
labor. This is one of the points which the physician bears
in mind when he examines the tongue of his patient.

44. The practice of eating at short intervals, or " between
meals," as it is called, has its disadvantage, as well as rapid
eating and over-eating, since it robs the stomach of its needed
period of entire rest, and thus overtasks its power. With
the exception of infants and the sick, no persons require
food more frequently than once in four hours. Severe
exercise either directly before or directly after eating retards
digestion ; a period of repose is most favorable to the proper
action of the stomach. The natural inclination to rest
after a hearty meal may be indulged, but should not be
carried to the extent of sleeping; since in that state the
stomach, as well as the brain and the muscles, seeks re-
lease from labor.

44. Eating between meals ? Severe exercise ? Sleep after meals }

/ ,4^*^*^-7?

u//sJe, &.

100 REVIEW QUESTIONS.

QUESTIONS FOR TOPICAL REVIEW.

PAGE

1. What do you understand by nutrition ? 80

2. How ie the process of nutrition carried on * 80

3. What further can you state on the subject ? 80, 81

4. Describe the general plan of digestion 81

5. How is the process of mastication carried on ? , 80, 82

ti. State what you can in relation to the formation of the teeth 82, 86

7. What, in relation to their arrangement ? &3, 84

8. What, in relation to the process of " shedding ?" 82, 83, 84

9. In relation to the different forms of teeth in different animals ? fc5

10. What causes operate to injure or destroy the teeth ? 85, 86

11. What suggestions and directions are given for the preservation of the

teeth ? 85, 86

12. What do you understand by insalivatiou ? 80, 86

13. How is the process of insalivation carried on ': 86, 87, 88

14. Of what importance is the saliva to the process ? 87, 88

15. Of what importance are mastication and insalivation ? 88, 89

16. Describe the consequences of rapid eating 89, 90

Y7. What becomes of the food directly after it has undergone mastication

and insalivation ? 90

18. Describe the location and formation of the stomach 90, 91, 92

19. Describe the process by which the gastric juice is formed '. 91

20. What are the properties and uses of the gastric juice ? 92

21. What are the movements of the stomach, and what their uses ? 92, 93

22. What further can you state on the subject ? 93

23. What portions of the food are digested in the stomach ? 93, 94

24. What are the first changes of digestion * 93

25. Describe the location and formation of the stomach 94

26. What further can you state in relation to the stomach ? 94

27. Descri be the process of intestinal digestion 94, 95, 96

28. What do you understand by absorption ? 80,- 96

29. How is the process of absorption effected ? 9(5, 97

30. What are the lacteals, and of what use are they * 96, 97

31. What length of time is required for the digestion of food ? 97, 98

32. What circumstances, of food, affect digestion ? 98

33. What circumstances, of emotion, affect digestion ? 98, 99

S4. What suggestions and directions are given upon the subject of eating

and drinking ? 98, 99

CIRCULATION OF TF1E BLOOD.
I H«Arl,Lungs, Arteries & Veins.]

THE CIRCULATION 101

CHAPTER VII. • ' • * > 5 . *« .1

T-HE CIRCULATION,

Tlie Blood — Its Plasma and Corpuscles — Coagulation of the Blood — The
Uses of the Blood — Transfusion — Change of Color — The Organs of
the Circulation — The Heart, Arteries, and Veins — The Cavities
and Valves of the Heart — Its Vital Energy — Passage of the Blood
through tfie Heart — The Frequency and Activity of its Movements —
The Pulse — The Spygmograph — The Capillary Blood-vessels— T/ie
Rate of the Circulation — Assimilation — Injuries to the Blood-vessels.

1. The Blood. — Every living organism of the higher
sort, whether animal or vegetable, requires for the main-
tenance of life and activity, a circulatory fluid, by which
nutriment is distributed to all its parts. In plants, this
fluid is the sap; in insects, it is a watery and colorless
blood; in reptiles and fishes, it is red but cold blood;
while in the nobler animals and man, it is the red and
warm blood.

2. The blood is the most important, as it is the most
abundant, fluid of the body ; and upon its presence, under
certain definite conditions, life depends. On this account
it is frequently, and very properly, termed "the vital
fluid." The importance of the blood, as essential to life,
was recognized in the earliest writings. In the narration
of the death of the murdered Abel, it is written, "the voice
of his blood crieth from the ground." In the Mosaic law,
proclaimed over thirty centuries ago, the Israelites were
forbidden to eat food that contained blood, for the reason
that "the life of the flesh is in the blood." With the
exception of a few tissues, such as the hair, the nails,
and the cornea of the eye, blood everywhere pervades the
body, as may be proven by puncturing any part with a

1. What is required by every living organism? In plants ? Insects? Reptiles*?
Man?

2. Importance and abundance of blood? Dependence of life ? Abel? Mosaic
law ? In what part of the body is blood not found ? Quantity of blood in the body ?

102

THE CIRCULATION:

Q«edle. The total quantity of blood in the body is esti-
mated at about one-eighth of its weight, or eighteen
pounds.

3. The color of the blood, in man and the higher ani-
mals, as is well known, is red ; but it varies from a bright
scarlet to a dark purple, according to the part whence it is
taken. " Blood is thicker than water," as the adage truly
states, and has a glutinous quality. It has a faint odor,
resembling that peculiar to the animal from which it is
taken.

4. When examined under the microscope, the blood no
longer appears a simple fluid, and its color is no longer red.
It is then seen to be made up of two distinct parts: first,
a clear, colorless fluid, called the plasma ; and secondly,
of a multitude of minute solid bodies, or corpuscles,
that float in the watery plasma. The plasma, or nutritive
liquid, is composed of water richly charged with materials
derived from the food, viz., ' albumen, which gives it
smoothness and swift motion; fibrin; certain fats; traces
of sugar; and various salts.

5. The Blood Corpus-
cles.— In man, these remark-
able "little bodies," as the
word corpuscles signifies, are
of a yellow color, but by their
vast numbers impart a red
hue to the blood. They are
very small, having a diameter
of about -j^Vo °f an inch, and
being one-fourth of that frac-
tion in thickness; 'so that if
3,500 of them were placed in
line, side by side, they would only extend one inch; or, if

FIG. 25.— THE BLOOD CORPUSCLES.

3. Color of blood? Its consistence ? Odor?

4. What is stated of the blood an viewed under the microscope ?

5. State what you can of the little bodies called corpuscles.

THE CIRCULATION

103

piled one above another, it would take at least 14,000 of
them to -stand an inch high. Although so small in size,
they are very regular in form. As seen under the micro-
scope, they are not globular or spherical, but flat, circular,
and disc-like, with central depressions on each side, some-
what like a pearl button that has not been perforated. In
freshly-drawn blood they show a disposition to arrange
themselves in little rolls like coins (Fig. 25).

6. The size and shape of the blood corpuscles vary in
different animals, so that it is possible to discriminate be-
tween those of man and the lower

animals (Fig. 26). This is a point of
considerable practical importance. (jP) c=>

For example, it is sometimes desir-
able to decide in a court of justice <a? #
the source, whether from man or an
inferior animal, of blood stains upon
the clothing of an accused person, or
upon some deadly weapon. This may
be done by a microscopical examina-
tion of a minute/portion of the dried
stain, previously refreshed by means
of gum-water. .Certain celebrated
cases are recorded in which the guilt
of criminals has been established, and
they have been condemned and pun- ^pvai corpusciesof a fowl,
ished upon the evidence which sci-
ence rendered on this single point,
the detecting of the human from
other blood.

7. The character of the blood of dead, extinct, and even
fossil animals, such as the mastodon, has been ascertained
by obtaining and examining traces of it which had been
shut up, perhaps for ages, in the circulatory canals of bone.
A means of detecting blood in minute quantities is found

FIG. 26.

6. The size and shape of the corpuscles ? Why is the fact important ?

7. The character of the blood of dead animals ? Means of detecting such blood ?

104 THE CIRCULATION.

in the spectroscope, the same instrument by which the
constitution of the heavenly bodies has been studied. If
a solution containing not more than one-thousandth part
of a grain of the coloring matter of the corpuscle, be ex-
amined, this instrument will detect it.

8. The corpuscles, just described, are known as the red
blood corpuscles. Besides these, and floating along in the
same plasma, are the white corpuscles. These are fewer
in number, but larger and globular in form. They are
colorless, and their motion is less rapid than that of the
other variety. The total number of both varieties of these
little bodies in the blood is enormous. It is calculated that
in a cubic inch of that fluid there are eighty-three mil-
lions, and at least five hundred times that number in ^he
whole body.

9. Coagulation. — The blood, in its natural condit n
in the body, remains perfectly fluid; but^ within a fe r
minutes after its removal from its proper vessels, whether
by accident or design, a change takes place. It begins to
coagulate, or assume a semi-solid consistence. If allowed
to stand, after several hours it separates into two distinct
parts, one of them being a dark red jelly, the coagulum,
or clot, which is heavy and sinks: and the other, a clear,
straw-colored liquid, called serum, which covers the clot.
This change is dependent upon the presence in the blood
of fibrin, which possesses the property of solidifying under
certain circumstances; one of these circumstances being
when the blood is separated from living tissues. The color
of the clot is due to the entanglement of the corpuscles
with the fibrin.

10. In this law of the coagulation of the blood is our
safeguard against death by haemorrhage, or against undue
loss of blood. If coagulation were impossible, the slight-

8. White corpuscles ? Total number of corpuscles in the body ?

9. The blood in its natural condition in the body ? Describe the process by
which the coagulation of blood takes place ?

1 0. If coagulation were impossible ? How is it in fact ?

THE CIRCULATION. 105

est injury in drawing blood would prove fatal. Whereas
now, in vastly the larger proportion of cases, bleeding
ceases spontaneously, because the blood, as it coagulates,
stops the mouths of the injured blood-vessels. In another
class of cases, where larger vessels are cut or torn, it is
simply necessary to close them by a temporary pressure ;
for in a few minutes the clot will form and seal them up.
In still more serious cases, where the blood-vessel is of
large size, the surgeon is obliged to tie a " ligature'' about
it, and thus prevent the force of the blood-current from
washing away the clots, which, forming within and around
the vessel, would close it effectually.

11. It is worthy of remark that this peculiarity is early
implanted in the blood, even before birth, and in advance
of any existing necessity for it; thus anticipating and
guarding against danger. But this is not all. Of most
of the inferior animals, which, as compared with man, are
quite helpless,*the blood coagulates more rapidly, and in
the case of the birds, almost instantly. The relative
composition of fluid and coagulated blood may be thus
«*< ^resented :

Fluid Blood. Coagulated Blood.

Plasma;.... Serum Serum

-Fibrin - ....
Corpuscles Corpuscles ...'-^-..Clot.

12. The Uses of the Blood.— The blood is the great
provider and purifier of the body. It both carries new
materials to all the tissues, and removes the worn out par-
ticles of matter. This is effected by the plasma. It both
conveys oxygen and removes carbonic acid. This is done-
through the corpuscles. Some singular experiments have

1 1 . What is worthy of remark ? Coagulation of the blood of inferior animals ':
Of the blood of birds ?

12. The blood, as a provider and purifier? What uses does the blood sub-
serve ? Experiments ? Transfusion ?

5*

106 THE CIRCULATION.

been tried to illustrate the life-giving power of the blood.
An animal that has bled so freely as to be at the point of
dying, is promptly brought back to life by an operation
called transfusion, by which fresh blood from a living
animal is injected into the blood-vessels of his body.

13. It is related that a dog, deaf and feeble from age,
had hearing and activity restored to him by the introduc-
tion into his veins of blood taken from a young dog ; and,
that a horse, twenty-six yea"rs old, having received the blood
of four lambs acquired new vigor. And further, that a dog,
just dead from an acute disease, was so far revived by trans-
fusion, as to be able to stand and make a few movements.

14. Transfusion has been practised upon man. At one
time, shortly after Harvey's discovery of the " Circulation
of the Blood," it became quite a fashionable remedy, it
being thought possible by it to cure all forms of disease,
and even to make the old young again. But these claims
were soon found extravagant, and many unhappy accidents
occurred in its practice ; so that being forbidden by govern-
ment and interdicted by the Pope, it rapidly fell into
disuse. At the present time, however, it is sometimes re-
sorted to in extreme cases, when there has been a great
and rapid loss of blood ; and there are upon record several
instances where, other means having failed, life has been
restored or prolonged by the operation of transfusion.

15. This reviving power of the blood seems to reside in
the corpuscles ; for transfusion, when attempted to be per-
formed with the serum alone, has, in every case, proved fruit-
less. Now, though so much depends upon the blood and
its corpuscles, it is a mistake to suppose that in them alone
is the seat of life, or that they are, in an exclusive manner,
alive. All the organs and parts of the body are mutually
dependent one upon the other; and the complete usefulness

13. The caee of the deaf and feeble dog ? Horse ? Dead dog ?

14. Transfusion, as a fashionable remedy ? What further of transfusion y

15. The seat of the reviving power of the blood ? What further is related

THE CIRCULATION. 107

of the blood, or of any other part, flows out of the har-
monious action of all the parts.

16. Change of Color. — The blood undergoes a variety
af changes in its journey through the system. As it visits
the different organs it both gives out and takes up mate-
rials. In one place it is enriched, in another it is impover-
ished. By reason of these alterations in its composition,
the blood also changes its color. In one part of the body
it is bright red, or arterial ; in another it is dark blue, or
venous. In the former case it is pure and fit for the sup-
port of the tissues ; in the latter, it is impure and charged
with effete materials. (The details of the change from
dark to bright will be given in the chapter on Respira-
tion.)

17. Circulation. — The blood is in constant motion
during life. From the heart, as a centre, a current is
always setting toward the different organs ; and from these
organs a current is constantly returning to the heart. In
this way a ceaseless circular movement is kept up, which is
called the Circulation of the Blood. This stream of the
vital fluid is confined to certain fixed channels, the blood-
vessels. Those branching from the heart are the arteries ;
those converging to it are the veins. The true course of
the blood was unknown before the beginning of the seven-
teenth century. In 1619 it was discovered by the illustri-
ous William Harvey. Like many other great discoverers,
he suffered persecution and loss, but unlike some of them,
he was fortunate enough to conquer and survive opposi-
tion. He lived long enough to see his discovery universally
accepted, and himself honored as a benefactor of mankind.

18. The Heart. — The heart is the central engine of
the circulation. In this wonderful little organ, hardly

1 G. Changes in the blood ? What further is stated ?

17. Motion of the blood? What is meant by the circulation of the blood*
How confined ? Discovery made by Harvey ?

18. Office of the heart? Location of the heart ? Its beat? Its shape? Pro-
tection to the heart ? What else i* t-n\d in relation to the heart ?

108

THE CIRCULATION.

FIG. i>7.— THE ORGANS OP CIRCULATION.

THE CIRCULATION.

109

larger than a man's fist, resides that sleepless force by
which, during the whole of life, the current of the blood
is kept in motion.
It is placed in the
middle and front
part of the chest,
inclining to the left
side. The heart-
beat may be felt and
heard between the
fifth and sixth ribs,
near the breast-bone.
Theshapeof Ihehenrl
is conical, with the
apex or point down-
ward and in front.
The base, which is
upward, is attached
so as to hold it se-
curely in its place,
while the apex is
freely moveable. In

Order that loSS of FIG. 28.— THE HEART AND LARGE VESSELS.

power from friction £ Sht Vent'icle' % A^"™16'
may be obviated, the F' Pulmonary Artcr*-

heart is enclosed between two layers of serous membrane,
which forms a kind of sac. This membrane is as smooth
as satin, and itself secretes a fluid in sufficient quantities
to keep it at all times well lubricated. The lining mem-
brane of the heart, likewise, is extremely delicate and
smooth.

19. The Cavities of the Heart.— The heart is hol-
low, and so partitioned as to contain four chambers or
cavities; two at the base, known as the auricles, from a

19. Formation of the heart ? Right and left heart ?

110

THE CIRCULATION.

fancied resemblance to the ear of a dog, and two at the
apex or point, called ventricles. An auricle and a ventricle

on the same side,
communicate with
each other, but there
is no opening from
side to side. It is
customary to regard
the heart as a double
organ, and to speak
of its division into
the right and left
heart. For while
both halves act to-
gether in point of
time, each half sus-
tains an entirely dis-
tinct portion of the
labor of the circu-
lation. Thus, the
right heart always
carries the dark or
venous blood, and the left always circulates the bright or
arterial blood.

20. If we examine the heart, we at once notice that
though its various chambers have about the same capacity,
the walls of the ventricles are thicker and stronger than
those of the auricles. This is a wise provision, for it is by
the powerful action of the former that the blood is forced
to the most remote regions of the body. The auricles, on
the contrary, need much less power, for they simply dis-
charge their contents into the cavities of the heart near at
hand and below them — into the ventricles.

FIG. 29.— SECTION OP THE HEART.

A, Right Ventricle

B, Left "

C, Right Auricle.

D, Left Auricle.

E, F, Inlets to the Ventricles.
G, Pulmonary Artery.
H, Aorta.

20. Capacity of the chambers of the heart ? What wise provision is men-
tioned ? The auricles ?

THE CIRCULATION. Ill

21. Action of the Heart.— The substance of the
heart is of a deep red color, and its fibres resemble those
of the voluntary muscles by which we move our bodies.
But the heart's movements are entirely involuntary. The
advantage of this is evident; for if it depended upon
us to will each movement, our entire attention would be
thus engaged, and we would find no time for study, pleas-
ure, or even sleep. The action of the heart consists in
alternate contractions- and dilatations. During contrac-
tion the walls come forcibly together, and thus drive out
the blood. In dilatation, they expand and receive a renewed
supply. These movements are called systole and diastole.
The latter may be called the heart's period of repose ; and
although it lasts only during two-fifths of a heart-beat, or
about a third of a second, yet during the day it amounts
to more than nine hours of total rest.

22. A remarkable property of the tissue of the heart is
its intense vitality. For while it is more constantly active
than any other organ of the body, it is the last to part
with its vital energy. This is especially interesting in
view of the fact that after life is apparently extinguished,
as from drowning, or poisoning by chloroform, there yet
lingers a spark of vitality in the heart, which, by contin-
ued effort, may be fanned into a flame so as to revivify the
whole body. In cold-blooded animals this irritability of
the heart is especially remarkable. The heart of a turtle
will pulsate, and the blood circulate for .a week after its
head has been cut off; and the heart will throb regularly
many hours after being cut out from the creature's chest.
The heart of a frog or serpent, separated entirely from the
body, will contract at the end of ten or twelve hours: that
of an alligator has been known to beat twenty-eight hours
after the death of the animal.

21. Substance of the heart? Its fibres? Its movements? The advantage
of such movements ? Action of the heart ? Its period of repose ?

22. Remarkable property of the tissue of the heart ? How shown ? How in-
teresting? In cold-blooded animals ? Heart of a turtle ? Of a frog? Alligator?

THE CIRCULATION.

23. Passage of the Blood through the Heart.—

Let us now trace the course of the blood through the
several cavities of the heart. In the first place, the venous
blood, rendered dark and impure by contact with the
changing tissues of the body, returns to the right heart
by the veins. It enters and fills the right auricle during
its dilatation : the auricle then contracts and fills the right
ventricle. Almost instantly, the ventricle contracts forcibly
and hurries the blood along the great artery of the lungs,
to be purified in those organs. Secondly, having completed
the circuit of the lungs, the pure and bright arterial blood
enters the left auricle. This now contracts and fills the left
ventricle, which cavity, in its turn, contracts and sends the
blood forth on its journey again through the system. This
general direction from right to left is the uniform and un-
deviating course of heart-currents.

24. The mechanism which enforces and regulates it, is
as simple as it is beautiful. Each ventricle has two open-
ings, an inlet and an outlet, each of which is guarded by
strong curtains, or valves. These valves open freely to
admit the blood entering from the right, but close inflex-
ibly against its return. Thus, when the auricle contracts,
the inlet valve opens ; but as soon as the ventricle begins
to contract, it closes promptly. The contents are then, so
to speak, cornered, and have but one avenue of escape,
that through the outlet valve into the arteries beyond. As
soon as the ventricle begins to dilate again, this valve
shuts tightly and obstructs the passage. The closing of
these valves occasions the two heart-sounds, which we hear
at the front of the chest.

25. Frequency of the Heart's Action.— The alter-
nation of contraction and dilation constitutes the heart-

23. Course of the blood through the heart ? Course of heart-currents ?

24. Openings of the ventricles ? How guarded ? How do the valves operate ?
The consequence ? Heart-sounds ?

25. Heart-beats? The heart as a susceptible organ? Heat, exercise, etc..'
Posture ?

THE CIRCULATION. 113

beats. These follow each other not only with great
regularity, but with great rapidity. The average number
in an adult man is about seventy-two in a minute. But
the heart is a susceptible organ, and many circumstances
affect its rate of action. Heat, exercise, and food will
increase its action, as cold, fasting, and sleep will decrease
it. Posture, too, has a curious influence; for if while sit-
ting, the beats of the heart number seventy-one; standing
erect will increase them to eighty-one, and lying down
will lower them to sixty-six.

26. The modifying influence of mental emotions is very
powerful. Sudden excitement of feeling will cause the
heart to palpitate, or throb violently. Depressing emotions
sometimes temporarily interrupt its movements, and the
person faints in consequence. Excessive joy, grief, or fear,
lias occasionally suspended the heart's action entirely, and
thus caused death. The rate of the heart-beat may be
naturally above or below seventy-two. Thus it is stated
that the pulse of the savage is always slower than that of
the civilized man. Bonaparte and Wellington were very
much alike in their heart's pulsations, which were less than
fifty in the case of each.

27. Activity of the Heart. — The average number of
heart-beats during a lifetime may be considered as at the
rate of seventy-two per minute, although this estimate is
probably low ; for during several years of early life the rate
is above one hundred a minute. In one hour, then, the
heart pulsates four thousand times ; in a day, one hundred
thousand times ; and in a year, nearly thirty-eight million
times. If we compute the number during a lifetime, thirty-
nine years being the present average longevity of civilized
mankind, we obtain as the vast aggregate, fourteen hun-
dred millions of pulsations.

26. Mental emotions ? Sudden excitement ? Excessive joy ? The heart-beat
rate ? Bonaparte and Wellington ?

27. Average number of heart-bears? In one hour ? Year? Lifetime?

114 THE CIRCULATION.

28. Again, if we estimate the amount of blood expelled
by each contraction of the ventricles, at four ounces, then
the weight of the blood moved during one minute will
amount to eighteen pounds. In a day it will be about
twelve tons; in a year, four thousand tons; and in the
course of a lifetime, over one hundred and fifty thousand
tons. These large figures indicate, in some measure, the
immense labor necessary to carry on the interior and vital
operations of our bodies. In this connection, we call to
mind the fanciful theories of the ancients in reference to
the uses of the heart. They regarded it as the abode of
the soul, and the source of the nobler emotions — bravery,
generosity, mercy, and love. The words courage and
cordiality are derived from a Latin word signifying heart.
Many other words and phrases, as hearty, heart-felt, to learn
by heart, and large-hearted, show how tenaciously these ex-
ploded opinions have fastened themselves upon our language.

29. At the present time the tendency is to ascribe purely
mechanical functions to the heart. This view, like the
older one, is inadequate; for it expresses only a small part
of our knowledge of this organ. The heart is unlike a
simple machine, because its motive power is not applied
from without, but resides in its own substance. Moreover,
it repairs its own waste, it lubricates its own action, and it
modifies its movements according to the varying needs of
the system. It is more than a mere force-pump, just as
the stomach is something more than a crucible, and the
eye something more than an optical instrument.

30. The Arteries. — The tube-like canals which carry
the blood away from the heart are the arteries. Their
walls are made of tough, fibrous materials, so that they
sustain the mighty impulse of the heart, and are not rup-
tured. In common with the heart, the arteries have a del-

28. Amount of blood expelled ? Theories of the ancients ?

29. The tendency at the present time ? Why is this view inadequate ''.

30. What arc the arteries ? Their walls? Their membraae I

THE CIRCULATION. 115

icately smooth lining membrane. They are also elastic,
and thus re-enforce the action of the heart : they always
remain open when cut across, and after death are always
found empty.

31. The early anatomists observed this phenomenon,
and supposing that the same condition existed during life,
came to the conclusion that these tubes were designed to
act as air-vessels, hence the name artery, from a Greek
word which signifies containing air. This circumstance
aifords us an illustration of the confused notions of the
ancients in reference to the internal operations of the
body. Cicero speaks of the arteries as "conveying the
breath to all parts of the body,"

32. The arterial system springs from the heart by a
single trunk, like a minute and hollow tree, with number-
less branches. As these branches leave the heart they
divide and subdivide, continually growing smaller and
smaller, until they can no longer be traced with the
naked eye. If, then, we continue the examination by the
aid of a microscope, we see these small branches sending-
off still smaller ones, until all the organs of the body are
penetrated by arteries.

33.. The Pulse. — With each contraction of the left
heart, the impulse causes a wave-like motion to traverse
the entire arterial system. If the arteries were exposed to
view, we might see successive undulations speeding from
the heart to the smallest of the branches, in about one-
sixth part of a second. The general course of the arteries
is as far as possible from the surface. This arrangement
is certainly wise, as it renders them less liable to injury,
the wounding of an artery being especially dangerous. It
also protects the arteries from external and unequal pres-
sure, by which the force of the heart would be counter*

3 1 . Early anatomist* ? The service of the illustration ?

32. The arterial system ? The branches and sub-branches of the arteries ?

33. Successive undulations from the heart ? Course of the arteries * Protec
tion of the arteries ? General location of the arteries ?

116' THE CIRCULATION.

acted and wasted. Accordingly, we generally find these
vessels hugging close to the bones, or hiding behind the
muscles and within the cavities of the body.

34. In a few situations, however, the arteries lie near the
surface ; and if we apply the finger to any of these parts,
we will distinctly feel the movement described, taking place
in harmony with the heart-beat. This is part of the wave-
motion just mentioned, and is known as the pulse. All
are more familiar with the pulse at the wrist, in the radial
artery ; but the pulse is not peculiar to that position, for it
may be felt in the carotid of the neck, in the temporal at
the temple, and elsewhere, especially near the joints.

35. Since the heart-beat makes the pulse, whatever
affects the former affects the latter also. Accordingly, the
pulse is a good index of the state of the health, so far as
.the health depends upon the action of the heart. It in-
forms the physician of the condition of the circulation in
four particulars: its rate, regularity, force, and fullness;
and nearly every disease modifies in some respect the con-
dition of the pulse. A very ingenious instrument, known
as the sphygmograph, or pulse-writer, has recently been
invented, by the aid of which the pulse is made to write
upon paper its own signature, or rather to sketch its own
profile. This instrument shows with great accuracy the

FIG. 30.— THE FORM OF THE PULSE.

difference between the pulses of health and those of disease.
In Fig. 30 is traced the form of the pulse in health, which
should be read from left to right. That part of the trace

3 i. Where do the arteries lie ? If we apply the finger * Pulse ? Where felt ?
35. The pulse as an index * Of what does it inform the physician ? Instrument
for recording pulsation t

THE CIRCULATION. 11

which is nearly perpendicular coincides with the contrac-
tion of the ventricles ; while the wavy portion marks their
dilatation.

36. The Veins. — The vessels which convey the blood
on its return to the heart are the veins. They begin in
the several organs of the body, and at first are extremely
small; but uniting together as they advance, they con-
stantly increase in size, reminding us of the way in which
the fine rootlets of the plant join together to form the
large roots, or of the rills and rivulets that flow together
to form the large streams and rivers. In structure, the
veins resemble the arteries, but their walls are compara-
tively inelastic. They are more numerous, and commu-
nicate with each other freely in their course, by means of
interlacing branches.

37. But the chief point of distinction is in the presence
of the valves in the veins. These are little folds of mem-
brane, disposed in such a way, that

they only open to receive blood
flowing toward the heart, and close
against a current in the opposite
direction. Their position in the
veins on the back of the hand may

be readily observed, if we first ob-pio 3( _THF VALVBR op THE
struct the return of blood by a cord VEINS.

tied around the forearm or wrist. In a few minutes the
veins will appear swollen, and upon them will be seen
certain prominences, about an inch apart. These latter
indicate the location of the valves, or, rather, they show
.that the vessels in front of the valves are distended by the
blood, which cannot force a passage back through them.

38. This simple experiment proves that the true direction
of the venous blood is toward the heart. That the color

36. What are the vein* ? How do they form ? What do they resemble ?

37. Valves in the veins ? What are they ? Their position ? Experiment with
the cord ?

38. What will be proved by the experiment ? What inference is drawn ?

118 THE CIRCULATION.

of the blood is dark, will be evident, if we compare the
hand thus bound by a cord with the hand not so bound.
It also proves that the veins lie superficially, while the
arteries are beneath the muscles, well protected from pres-
sure ; and that free communication exists from one vein to
another. If now we test the temperature of the constricted
member by means of a thermometer, we will find that it is
colder than natural, although the amount of blood is
larger than usual. From this fact we infer, that whatever
impedes the venous circulation tends to diminish vitality ;
and hence, articles of clothing or constrained postures,
that confine the body or limbs, and hinder the circulation
of the blood, are to be avoided as injurious to the health.

39. The Capillaries. — A third set of vessels completes
the list of the organs of the circulation, namely, the capil-
lary vessels, so called (from the Latin word capillarix,
hair-like), because of their extreme fineness. They are,
however, smaller than any hair, having a diameter of about
Tntair °f an inch, and can only be observed by the use of the
microscope. These vessels may be regarded as the connect-
ing link between the last of the arteries and the first of
the veins. The existence of these vessels was unknown to
Harvey, and was the one step wanting to complete his
great work. The capillaries were not discovered until
1661, a short time after the invention of the microscope.

40. The circulation of the blood, as seen under the
microscope, in the transparent web of a frog's foot, is a
spectacle of rare beauty, possessing more than ordinary
interest, when we consider that something very similar
is taking place in our own bodies, on a most magnificent,
scale. It is like opening a secret page in the history of
our own frames. We there see distinctly the three classes
of vessels with their moving contents; first, the artery,

39. Capillaries? How regarded ? Harvey?

40. The circulation of the blood in the web of a frog's foot? Describe it.
How general is the existence of the tissues t

THE CIRCULATION".

119

with its torrent of blood rushing down from the heart,
secondly, the vein, with its slow, steady stream flowing in
the opposite direction ; and between them lies the network
of capillaries, so fine that the corpuscles can only pass
through "in single file." The current has here an uncer-
tain or swaying motion, hurrying first in one direction, then
hesitating, and then turning back in the opposite direction,

FIG. ;«.— WEB op A FROG'S FOOT, FIG. .33.— MARGIN OP FROG'S W
slightly magnified. magnified 30 diameters.

and sometimes the capillaries contract so as to be entirely
empty. Certain of the tissues are destitute of capillaries ;
such are cartilage, hair, and a few others on the exterior of
the body. In all other structures, networks of these vessels
are spread out in countless numbers : so abundant is the
supply, that it is almost impossible to puncture any part
with the point of a needle without lacerating tens, or even
hundreds of these vessels.

41. The capillaries are elastic, and may so expand as to
produce an effect visible to the naked eye. If a grain of
sand, or some other foreign particle, lodge in the eye, it will
become irritated, and in a short time the white of the eye
will be "blood-shot." This appearance is due to an in-

41. Elasticity of the capillaries? Grain of sand in the eye? Blush? Other
cases ?

T20 THE CIRCULATION.

crease in the size of these vessels. A blush is another exam-
ple of this, but the excitement comes through the nervous
system, and the cause is some transient emotion, either of
pleasure or pain. Another example is sometimes seen in
purplish faces of men addicted to drinking brandy ; in
them the condition is a congestion of the capillary circula-
tion, and is permanent, the vessels having lost their power
of elastic contraction.

42. Rapidity of the Circulation. — That the blood
moves with great rapidity is evident from the almost instant
effects of certain poisons, as prussic acid, which act
through the blood. Experiments upon the horse, dog,
and other inferior animals, have been made to measure
its velocity. If a substance, which is capable of a distinct
chemical reaction (as potassium ferrocyanide, or barium
nitrate), be introduced into a vein of a horse on one side,
and blood be taken from a distant vein on the other side,
its presence may be detected at the end of twenty or thirty-
two seconds. In man, the blood moves with greater speed,
and the circuit is completed in twenty-four seconds.

43. What length of time is required for all the blood of
the body to make a complete round of the circulation?
This question cannot be answered with absolute accuracy,
since the amount of the blood is subject to continual
variations. But, if we assume this to be one-eighth of the
weight of the body, about eighteen pounds, it will be suf-
ficiently correct for our purpose. Now to complete the
circuit, this blood must pass once through the left ventricle,
the capacity of which is two ounces. Accordingly, we find
that, under ordinary circumstances, all the blood makes one
complete rotation every two minutes; passing successively
through the heart, the capillaries of the lungs, the arteries,
the capillaries of the extremities, and through the veins.

42. Show what time is required for a given portion of blood to travel once
around the body.

43. Time required for all the blood to circulate completely around?

THE CIRCULATION.

44. Assimilation. — The crowning act of the circula-
tion, the furnishing of supplies to the different parts of
the body, is effected by means of the capillaries. The or-
gans have been wasted by use ; the blood has been enriched,
by the products of digestion. Here, within the meshes of
the capillary network, the needy tissues and the needed
nutriment are brought together. By some mysterious
chemistry, each tissue selects and withdraws from the
blood the materials it requires, and converts them into a
substance like itself. This conversion of lifeless food into
living tissue is called assimilation. The process probably
takes place at all times, but the period especially favorable
for it is during sleep. Then the circulation is slower, and
more regular, and most of the functions are at rest. The
body is then like some trusty ship, which after a long voy-
age is "hauled up for repairs."

45. Iiyuries to the Blood-vessels. — It is important
to be able to discriminate between an artery and a vein, in
the case of a wound, and if we remember the physiology
of the circulation we may readily do so. For, as we have
already seen, haemorrhage from an artery is much more
dangerous than that from a vein. The latter tends to cease
spontaneously after a short time. The arterial blood flows
away from the heart with considerable force, in jets; its
color being bright scarlet. The venous blood flows toward
the heart from that side of the wound furthest from the
heart; its stream being continuous and sluggish; its color
dark. In an injury to an artery, pressure should be made
between the heart and the wound ; and in the case of a
vein that persistently bleeds, it should be made upon the
vessel beyond its point of injury.

44. What is meant by assimilation ? What can you say of its use, etc. ? Time ?

45. What is stated of the injuries to the blood-vessels ?

REVIEW QUESTION'S.

QUESTIONS FOR TOPICAL REVIEW.

PAGE

1. In what organisms is the so-called circulatory fluid found ? ............... 101

2. How is it designated in the different organisms ? .......................... 101

3. What can you state of the importance of blood to the body ? .......... 101, 105

4. Of its great abundance, color, and composition ? .................. 101, 102, 107

5. Describe the corpuscles of the human blood ............... ...... 102, 103, 104

6. What is said of them in comparison with those of the lower animals ?. . . 103

7. Of the importance of sometimes detecting human from other blood ? ...... 10-3

8. What means have we of detecting blood in spots or stains ? ........... 103, 104

9. What is meant by coagulation of the blood ? ............................... 104

10. What wisdom is there in the law of the blood's coagulation 5- ......... 104 105

11. How is this wisdom made manifest ? ...................................... 105

12. In what cases is the aid of the surgeon required ? ......................... 105

13. What are the two g: eat uses of the blood ? ................................. 105

14. Through what mediums is the blood provided with new material and re-

lieved of the old material ? .............................................. 105

15. What do you understand by the operation called transfusion ? ........... 106

16. What cases of transfusion are reported of the lower animals ? ............. 100

17. What can you state of transfusion as practised upon man ? ................ 106

18. What further can you say on the subject ? ............................. 106, 107

19. What changes take place in the color of the blood in its journey through

the system ? .................................. . .......................... 107

20. State all you can in relation to the circulation of the blood ................ 107

21. All, in relation to the size, shape, and location of the heart ........... 107, 109

22. How is the loss of power in the heart movements obviated ? ....... ...... 109

23. Give a description of the formation of the heart .......... , ....... 109, 110, 111

21. What can you state of the ventricles and auricles of the heart ? ............ 110

25. Describe the action of the heart ................ . .......................... Ill

26. What special vitality does the tissue of the heart possess ? ................. Ill

27. State all you can on the subject ........................................... Ill

28. Describe the course of the blood through the cavities of the heart ......... 112

29. Describe the mechanism that regulates the heart-currents ........ . ....... 112

30. How do you account for the two heart-sounds at the front of the chest ?. . . 112

31. State what you can of the frequency of the heart's action ............. 112, 113

32. Of the activity of the heart .......................................... 113, 114

33. What do you understand by the arteries ? ............................ 114, 115

34. State what you can of the arteries and the arterial system ............. 114, 115

35. What do you understand by the pulse ? ................................ 115, 116

30. In what part of the body may the pulse be felt ? .......................... 116

37. What further can you state of the pulse ? .............................. 116, 117

SS. What are the veins ? ...................................................... 117

39. Where do they exist, and how arc they formed ? ........................... 117

40. Describe the valves of the veins and their uses ............................ 117

41. Now give a full description of the construction of the veins ............... 117

42. What further can you siate of the veins? .............................. 117, 119

-13. What do you understand by the capillaries ? .......................... 118, 119

44 What service do the capillaries perform ? ........................ 118, 110, 121

45. Describe the circulation of the blood in the region of the heart ....... 118, 119

46. What can you state of the rapidity of the blood's circulation ? ............. 120

47. Of the process known as assimilation ? ................................... 121

48. Of injuries to the blood-vessels * ........ ............................... 121

RESPIRATION. 123

CHAPTER VIII.
RESPIRATION.

The Objects of Respiration — The Lungs — The Air-Passages — The Move-
ments of Respiration — Expiration, and Inspiration — The Frequency
of Respiration — Capacity of the Lungs — The Air we breathe —
Changes in the Air from Respiration — Changes in the Blood — In-
terchange of Oases in the Lungs — Comparison between Arterial and
Venous Blood — Respiratory Labor — Impurities of the Air — Dust —
Carbonic Acid — Effects of Impure Air — Nature's Provision for
Purifying tJie Air — Ventilation — Animal Heat — Spontaneous Com-
bustion.

1. The Object of Respiration. — In one set of capil-
laries, or hair-like vessels, the blood is impoverished for the
support of the different members and organs of the body.
In another capillary system the blood is refreshed and again
made fit to sustain life. The former belongs to the greater
or systemic circulation ; the latter to the lesser or pulmo-
nary, so called from pulmo, the lungs, in which organs it
is situated. The blood, as sent from the right side of the
heart to the lungs, is venous, dark, impure, and of a nature
unfit to circulate again through the tissues. But, when
the blood returns from the lungs to the left side of the
heart, it has become arterial, bright, pure, and no longer
hurtful to the tissues. This marvellous purifying change
is effected by means of the very familiar act of respiration,
or breathing.

2. The Lungs. — The lungs are the special organs of
respiration. There are two of them, one on each side of
the chest, which cavity they, with the heart, almost wholly
occupy. The lung-substance is soft, elastic, and sponge-
like. Under pressure of the finger, it crepitates, or crackles,
and floats when thrown into water ; these properties being

1 . Difference between the two sets of capillaries ? Change effected by respira-
tion or breathing?

2. What are the lungs? How many lungs are there? Lung-substance? Its
properties ? The pleura ?

124

RESPIRATION.

due to the presence of air in the minute air-cells of the
lungs. To facilitate the movements necessary to these
organs, each of them is provided with a double covering of
an exceedingly smooth and delicate membrane, called the

FIG. 34.— ORGANS or THE CHEST.

A, Lungs.

B, Heart.

D, Pulmonary Artery.

E, Trachea.

pleura. One layer of the pleura is attached to the walls
of the chest, and the other to the lungs; and they glide,
one upon the other, with utmost freedom. Like the mem-
brane which envelops the heart, the pleura secretes its own
lubricating fluid, in quantities sufficient to keep it alwaye
moist.

3. The Air-Passages. — The lungs communicate with
the external air by means of certain air-tubes, the longest of

3. Communication of the lungs with the external air ? Bronchial tubes ?

RESPIRATION.

which, the trachea, or windpipe, runs along the front of tl
neck (Fig. 34, E, and 35) .With-
in the chest this tube divides
into two branches, one entering
each lung; these in turn give
rise to numerous branches, or
bronchial tubes, as they are
called, which gradually dimin-
ish in size until they are about
one- twenty-fifth of an inch in
diameter. Each of these ter-
minates in a cluster of little
pouches, or "air-cells," having
very thin walls, and covered
with a capillary network, the
most intricate in the body
(Fig. 36).

4. These tubes are some-
what flexible, sufficiently so to
bend when the parts move in
which they are situated ; but
they are greatly strengthened
by bands or rings of cartilage
which keep the passages always
open; otherwise there would
be a constantly-recurring ten-
dency to collapse after every
breath. The lung-substance
essentially consists of these
bronchial tubes and terminal
air-cells, with the blood-ves-
sels ramifying . about them
(Fig. 37). At the top of the

v . ,! , , „ FIG. 36.— DIAGRAM AND SECTION OP

trachea is the larynx, a sort of THE AIR-CELLS.

PIG. 35.— LARYNX, TBACHEA, AND
BRONCHIAL TUBES.

4. Office of the bronchial tubes ? What further can you state of them ?

126 RESPIRATION.

box of cartilage, across which are stretched the vocal cords.
Here the voice is produced chiefly by the passage of the
respired air over these cords, causing them to vibrate.

FIG. 37. — SECTION OF THE LUNGS.

5. Over the opening of the larynx is found the epiglottis,
which fits like the lid of a box at the entrance to the
lungs, and closes during the act of swallowing, so that
food and drink shall pass backward to the oesophagus, or
gullet (Fig. 38). Occasionally it does not close in time,
and some substance intrudes within the larynx, when we at
once discover, by a choking sensation, that "something has
gone the wrong way," and, by coughing, we attempt to ex-
pel the unwelcome intruder. The epiglottis is one of the
many safeguards furnished by nature for our security and

5. The epiglottis ? When it does not close in time, what is the consequence?

RESPIRATION.

12?

comfort, and is planned and put in place long before these
organs are brought into actual use in breathing and in
taking food.

FIG. 38.— SECTION OP MOUTH AND THROAT.
A, The Tongue. C, Vocal C9rd. N, Trachea.

B, The Uvula.

E, Epiglottis.
L, Larynx.

O, (Esophagus.

6. The air -passages are linea tnrough nearly their
whole extent with mucous membrane, which maintains
these parts in a constantly moist condition. This meni-
brane has a peculiar kind of cells upon its outer stir-

6. Lining of the air-passages? Ciliated cells? Their uses? The three dis-
eases of the lungs ?

128 RESPIRATION.

face. If examined under a powerful microscope, we may
see, even for a considerable time after their removal from
the body, that these cells have minute hair-like processes
in motion, which wave like a field of grain under the
influence of a breeze (Fig. 39). This is a truly beauti-
ful sight; and since it is found that these little cilia, as
they are called, always produce currents in one direction,
from within outward, it is probable that they serve a

useful purpose in catching and
carrying away from the lungs
dust and other small particles
drawn in with the breath (Fig.
39). The three diseases which
more commonly affect the lungs,
as the result of exposure, are
FIG. 39.-ciLiATEi> CELLS. pneumonia, or inflammation of
the lungs, implicating principally

the air-cells; bronchitis, an inflammation of the large bron-
chial tubes; and pleurisy, an inflammation of the investing
membrane of the lungs, or pleura. Among the young, an
affection of the trachea takes place, known as croup.

7. The Movements of Respiration.— The act of
breathing has two parts — (1), inspiration, or drawing
air into the lungs, and (2), expiration, or expelling it
from the lungs again. In inspiration, the chest extends
in its length, breadth, and height, or width. We can
prove that this is the case as regards the two latter, by
observing the effect of a deep breath. The ribs are ele-
vated by means of numerous muscles, some of which oc-
cupy the entire spaces between those bones. But the
increase in length, or vertically, is not so apparent, as it is
caused by a muscle within the body called the diaphragm,
it being the thin partition which separates the chest from
the abdomen, rising like a dome within the chest. (Fig. 16).

7. The act of breathing ? Extension of the chest by breathing ?

RESPIRATION.

8. With every inspiration, the diaphragm contracts, and
in so doing, approaches more nearly a plane, or horizontal,
surface, and thus enlarges the capacity of the chest.
Laughing, sobbing, hiccoughing, and sneezing are caused
by the spasmodic or sudden contraction of the diaphragm.
The special power of this muscle is important in securing
endurance, or " long wind," as it is commonly expressed;
which may be obtained mainly by practice. It is possessed
in a marked degree by the mountaineer, the oarsman, and
the trained singer. As the walls of the chest extend, the
lungs expand, and the air rushes in to fill them. This
constitutes an inspiration. The habit of taking frequent
and deep inspirations, in the erect position, with the
shoulders thrown back, tends greatly to increase the ca-
pacity and power of the organs of respiration.

9. Expiration is a less powerful act than inspiration.
The diaphragm relaxes its contraction, and ascends in the
form of a dome; the ribs descend and contract the chest;
while the lungs themselves, being elastic, assist to drive
out the air. The latter passes out through the same chan-
nels by which it entered. At the end of each expiration
there is a pause, or period of repose, lasting about as long
as the period of action.

10. Frequency of Respiration. — It is usually esti-
mated that we breathe once during every four beats of the
heart, or about eighteen times in a minute. There is, of
course, a close relation between the heart and lungs, and
whatever modifies the pulse, in like manner affects the
breathing. When the action of the heart is hurried, a
larger amount of blood is sent to the lungs, and, as the
consequence, they must act more rapidly. Occasionally,
the heart beats so very forcibly that the lungs cannot keep
pace with it, and then we experience a peculiar sense of

8. Contraction of the diaphragm ? Power of the diaphragm? Effects of ex-
tending the wails of the chest ? The habit of taking frequent and deep inspirations '(

9. Expiration ? The mechanism of expiration ?

1O. Frequency of respiration ? Effect of hurried action of the heart?

6*

130 RESPIRATION.

distress from the want of air. This takes place when we
run until we are " out of breath.7' At the end of every
fifth or sixth breath, the inspiration is generally longer
than usual, the effect being to change more completely the
air of the lungs.

11. Although, as a general rule, the work of respiration
goes on unconsciously and without exertion on our part,
it is nevertheless under the control of the will. We can
increase or diminish the frequency of its acts at pleasure,
and we can "hold the breath," or arrest it altogether
for a short time. From twenty to thirty seconds is
ordinarily the longest period in which the breath can be
held ; but if we first expel all the impure air from the
lungs, by taking several very deep inspirations, the time
may be extended to one and a half or even two minutes.
This should be remembered, and acted upon, before pass-
ing through a burning building, or any place where the
air is very foul. The arrest of the respiration may be still
further prolonged by training and habit ; thus it is said,
the pearl-fishers of India can remain three or four minutes
under water without being compelled to breathe.

12. Capacity of the Lungs. — The lungs are not
filled and emptied by each respiration. For while their
full capacity, in the adult, is three hundred and twenty
cubic inches, or more than a gallon, the ordinary breath-
ing air is only one-sixteenth part of that volume, or twenty
cubic inches, being two-thirds of a pint. Accordingly, a
complete renovation, or rotation, of the air of the lungs
does not take place more frequently than about once in a
minute ; and by the gradual introduction of the external
air, its temperature is considerably elevated before it
reaches the delicate pulmonary capillaries. In tranquil
respiration, less than two-thirds of the breathing power is

1 1 . Respiration controlled by the will ? Advantage of the knowledge to us ?

12. Capacity of the lungs ? Time required to renovate the air in the lungs ?
In tranquil respiration ? Importance of the provision ?

RESPIRATION. 131

called into exercise, leaving a reserve capacity of about one
hundred and twenty cubic inches, equivalent to three and
one half pints. This provision is indispensable to the con-
tinuation of life; otherwise, a slight embarrassment of res-
piration, by an ordinary cold, for instance, would suffice
to cut off the necessary air, and the spark of life would
be speedily extinguished.

13. The Air we breathe.— The eartfi is enveloped
on all sides by an invisible fluid, called the atmosphere.
It forms a vast and shoreless ocean of air, forty-five miles
deep, encircling an4 pervading all objects on the earth's
surface, which is absolutely essential for the preservation of
all vegetable and animal life, — in the sea, as well as on the
land and in the air. At the bottom, or in the lower strata
of this aerial ocean, we move and have our being. Per-
fectly pure water will not support marine life, for a fish
may be drowned in water from which the air has been ex-
hausted, just as certainly as a mouse, or any other land
animal, will perish if put deeply into the water for a length
of time. The cause is the same in both cases : the animal
is deprived of the requisite amount of air. It is also stated,
that if the water-supply of the plant be deprived of air, its
vital processes are at once checked.

14. The air is not a simple element, as the ancients sup-
posed, but is formed by the mingling of two gases, known
to the chemist as oxygen and nitrogen, in the proportion
of one part of the former to four parts of the latter. These
gases are very unlike, being almost opposite in their prop-
erties: nitrogen is weak, inert, and cannot support life;
while oxygen is powerful, and incessantly active ; and is the
essential element which gives to the atmosphere its power
to support life and combustion. The discovery of this fact
was made bv the French chemist, Lavoisier, in 1778.

13. The atmosphere ? How high or deep ? How essential to life ? Marine lift
in perfectly pure water and air ?

14. Composition of the air ? Properties of the two gases ?

132 RESPIRATION.

15. Changes in the Air from Respiration. — Air

that has been once breathed is no longer fit for respiration.
An animal confined within it will sooner or later die; so
too, a lighted candle placed in it will be at once extin-
guished. If we collect a quantity of expired air and ana-
lyze it, we shall find that its composition is not the same
as that of the inspired air. When the air entered the
lungs it was rich in oxygen ; now it contains twenty-five
per cent, less of that gas. Its. volume, however, remains
nearly the same ; its loss being replaced by another and
very different gas, which the lungs exhaled, called carbonic
acid, or, as the chemist terms it, carbon dioxide.

16. The expired air has also gained moisture. This is
noticed when we breathe upon a mirror, or the window-
pane, the surface being tarnished by the condensation of
the watery vapor exhaled by the lungs. In cold weather,
this causes the fine cloud which is seen issuing from the
nostrils or mouth with each expiration, and contributes in
forming the feathery crystals of ice which decorate our
window-panes on a winter's morning.

17- This watery vapor contains a variable quantity of
animal matter, the exact nature of which is unknown; but
when collected it speedily putrefies and becomes highly
offensive. From the effects, upon small animals, of con-
finement in their own exhalations, having at the same
time an abundant supply of fresh air, it is believed that
the organic matters thrown off by the lungs and skin
are direct and active poisons; and that to such emana-
tions from the body, more than to any other cause, are
due the depressing and even fatal results which follow the
crowding of large numbers of persons into places of lim-
ited capacity.

1 !i. Air once breathed ? An animal in it ? A candle ? Analysis of expired air ?
Change in volume ?

1 6. What else has the expired air pained ? When and where noticed ?

17. Nature of the watery vapor ? Its effects upon animals ?

R-ESPIRATIOtf. 133

18. History furnishes many painful instances of the ill
effects of overcrowding. In 1756, of one hundred and
forty-six Englishmen imprisoned in the Black Hole of
Calcutta, only twenty-three, at the end of eight hours,
survived. After the battle of Austerlitz, three hundred
prisoners were crowded into a cavern, where, in a few
hours, two-thirds of their number died. On board a
steam-ship, during a stormy night, one hundred and
fifty passengers were confined in a small cabin, but
when morning came, only eighty remained alive.

19. Changes in the Blood from Respiration.—
The most striking change which the blood undergoes by
its passage through the lungs, is the change of color from
a dark blue to bright red. That this change is dependent
upon respiration has been fully proved by experiment.
If the trachea, or windpipe, of a living animal be so com-
pressed as to exclude the air from, the lungs, the blood in
the arteries will gradually "grow darker, until its color is
thelrame as that of the venous blood. When the pressure
is removed the^ blood speedily resumes its bright hue.
Again, if the animal be made to. breathe an atmosphere
containing more oxygen than atmospheric air, the color
changes from scarlet to vermilion, and becomes even
brighter than arterial blood. This change of color is not
of itself a very important matter, but it indicates a most
important change of composition.

20. The air, as we have seen, by respiration loses oxy-
gen and gains carbonic acid : the blood, on the contrary,
gains oxygen and loses carbonic acid. The oxygen is the
food of the blood corpuscles; while the articles we eat and
drink belong more particularly to the plasma of the blood.
The air, then, it is plain, is a sort of food, and we should

18. Give some of the instances furnished by history.

If). Change in the blood from blue to red. Upon what does the change depend ?
How shown ?

2O. What does the air lose and gain by respiration ? What, the blood ? Air as
food?

134 RESPIRATION.

undoubtedly so regard it, if it were not for the fact that
we require it constantly, instead of taking it at stated in-
tervals, as is the case with our articles of diet. Again, as
the demand of the system for food is expressed by the sen-
sation of hunger, so the demand for air is marked by a
painful sensation called suffocation.

21. Interchange of Gases in the Lungs. — As the
air and the blood are not in contact, they being separated
from each other by the walls of the air-cells and of the
blood-vessels, how can the two gases, oxygen and carbonic
acid, exchange places ? Moist animal membranes have a
property which enables them to transmit gases through
their substance, although they are impervious to liquids.
This may be beautifully shown by suspending a bladder
containing dark blood in a jar of oxygen. At the end of
a few hours the oxygen will have disappeared, the blood
will be brighter in color, and carbonic acid will be found
in the jar.

22. If this interchange takes place outside of the body,
how much more perfectly must it take place within, where
it is favored by many additional circumstances! The
walls of the vessels and the air-cells offer no obstacle to
this process, which is known as gaseous diffusion. Both
parts of the process are alike of vital importance. If oxy-
gen be not received, the organs cease to act; and if car-
bonic acid be retained in the blood, its action is that of a
poison ; unconsciousness, convulsions, and death follow-
ing.

23. Difference between Arterial and Venous
Blood. — The following table presents the essential points
of difference in the appearance and composition of the
blood, before and after its passage through the lungs : —

21 . Moist animal membranes ? How shown with the bladder ?

22. Gaseous diffusion? If oxygen be not received? If carbonic acid be re-
tained?

23. Difference in the appearance and composition of the blood? Temperature
of the hlood ? The blood while passing through the lungs ? The consequence ?

RESPIRATION. 135

Venous Blood.

Arterial Blood.

Color,

Dark blue,

Scarlet.

Oxygen,

8 per cent,

18 per cent.

Carbonic Acid,

15 to 20 per cent.,

6 per cent., or less.

Water,

More,

Less.

The temperature of the blood varies considerably; but
the arterial stream is generally warmer than the venous.
The blood imparts heat to the air while passing through
the lungs, and consequently the contents of the right side
of the heart has a higher temperature than the contents
on the left side.

24. By means of the spectroscope, we learn that the
change of color in the blood has its seat in the corpuscles ;
and that, according as they retain oxygen, or release it, they
present the spectrum of arterial or venous blood. There
evidently exists, on the part of these little bodies, an affin-
ity for this gas, and hence they have been called " carriers
of oxygen." It was long ago thought that blue blood was
a trait peculiar to persons of princely and royal descent,
and boastful allusions to the " sang azure" of kings and
nobles are quite often met with. Physiology, however, in-
forms us that blue blood flows in the veins of the low as
well as the high, and that so far from its presence indicat-
ing a mark of purity, it, in reality, represents the waste and
decay of the system.

25. Amount of Respiratory Labor. — During or-
dinary calm respiration, we breathe eighteen times in a
minute; and twenty cubic inches of air pass in and out of
the lungs with every breath. This is equivalent to the use
of three hundred and sixty cubic inches, or more than ten
pints of air each minute. From this we calculate that the
quantity of air which hourly traverses the lungs is about
thirteen cubic feet, or seventy-eight gallons; and daily, not

24. What do we learn by means of the spectroscope ? " Carriers of oxygen ?"
Blue blood in the system ?

25. The amount of air that passes in and out of the lungs ?

136 RESPIRATION.

less than three hundred cubic feet, an amount nearly equal '
to the contents of sixty barrels.

26. Of this large volume of air five per cent, is absorbed
in its transit through the lungs. The loss thus sustained is
almost wholly of oxygen, and amounts to fifteen cubic feet
daily. The quantity of carbonic acid exhaled by the lungs
during the day is somewhat less, being twelve cubic feet.
Under the influence of excitement or exertion, the breath-
ing becomes more frequent and more profound ; and then
the internal respiratory work increases proportionately,
and may even be double that of the above estimate. It
has been estimated that in drawing a full breath, a man
exerts a muscular force equal to raising two hundred
pounds placed upon the chest.

27. Impurities of the Air. — The oxygen in the at-
mosphere is of such prime importance, and its proportion
is so nicely adjusted to the wants of man, that any gas or
volatile substance which supplants it must be regarded as
a hurtful impurity. All gases, however, are not alike in-
jurious. Some, if inhaled, are necessarily fatal ; arsen-
uretted hydrogen being one of these, a single bubble of
which destroyed the life of its discoverer, Gehlen. Others
are not directly dangerous, but by taking the place of
oxygen, and excluding it from the lungs, they become so.
Into this latter class we place carbonic acid.

28. Most of the actively poisonous gases have a pungent
or offensive odor; and, as may be inferred, most repugnant
odors indicate the presence of substances unfit for respira-
tion. Accordingly, as we cannot see or taste these impu-
rities, the sense of smell is our principal safeguard against
them ; and we recognize the design which has planted this
sense, like a sentinel at the proper entrance of the air-

26. Air absorbed in its transit through the lungs ? The loss ? Carbonic acid
exhaled ? Effect of excitement or exertion ? What estimate ?

27. Importance of the oxygen in the atmosphere? Injurious character of

28. Pungency of gases ? The inference ? Our safeguard ?

RESPIRATION. 137

passages, the nostrils, to give as warning of approaching
harm. Take, as an example, the ordinary illuminating
gas of cities, from which so many accidents happen. How
many more deaths would it cause if, when a leak occurs,
we were not able to discover the escape of the gas by means
of its disagreeable odor.

29. Organic matters exist in increased measure in the
expired breath of sick persons, and impart to it, at times, a
putrid odor. This is especially true in diseases which,
like typhus and scarlet fever, are • referable to a blood
poison. In such cases the breath is one of the -means by
which nature seeks to expel the offending material from
the system. Hence, those who visit or administer to fever-
sick persons should obey the oft-repeated direction, " not
to take the breath of the sick." At such times, if ever,
fresh air is demanded, not alone for the sick, but as well
for those who are in attendance.

30. Dust in the Air. — Attention has lately been di-
rected to the dust, or haze, that marks the ray of sunshine
across a shaded room. Just as, many years ago, it was dis-
covered that myriads of animalcula infested much of the
water we drank, so now the microscope reveals "the gay
motes that dance along a sunbeam" to be, in part, com-
posed of multitudes of animal and vegetable forms of a
very low grade, the germs of fermentation and putrefac-
tion, and the probable sources of disease.

31. It is found that the best filter by which to separate
this floating dust from the air is cotton wool, although a
handkerchief will imperfectly answer the same purpose.
In a lecture on this subject by Prof. Tyndall, he remarks
that, " by breathing through a cotton wool respirator, the
noxious air of the sick room is restored to practical purity.
Thus filtered, attendants may breathe the air unharmed.

29. The air of rooms in which fever-sick persons are confined ?

30. Animalcula in the water? Dust in the air ?

3 1 . The best, air filter ? The remarks of Prof. Tyndall ?

138 RESPIRATION.

In all probability, the protection of the lungs will be the
protection of the whole system. For it is exceedingly
probable that the germs which lodge in the air-passages
are those which sow epidemic disease in the body. If this
be so, then disease can certainly be warded oif by niters of
cotton wool. By this means, so far as the germs are con-
cerned, the air of the highest Alps may be brought into
the chamber of the invalid."

32. Carbonic Acid in the Air. — We have already
spoken of this gas as -an exhalation from the lungs, and a
source of impurity; but it exists naturally in the atmos-
phere in the proportion of one half part per thousand. In
volcanic regions it is poured forth in enormous quantities
from fissures in the earth's surface. Being heavier than
air, it sometimes settles into caves and depressions in the
surface. It is stated that in the island of Java, there is a
place called the " Valley of Poison," where the ground is
covered with the bones of birds, tigers, and other wild ani-
mals, which were suffocated by carbonic acid while passing.
The Lake Avernus, the fabled entrance to the infernal re-
gions, was, as its name implies, bird-less, because the birds,
while flying over it, were poisoned by the gas and fell dead
into its waters. In mines, carbonic acid forms the dreaded
choke-dam}), while carburetted hydrogen is the fire-damp.

33. In the open air, men seldom suffer from carbonic
acid, for, as we shall see presently, nature provides for its
rapid distribution, and even turns it to profitable use.
But its ill effects are painfully evident in the abodes of
men, in which it is liable to collect as the waste product of
respiration and of that combustion which is necessary for
lighting and warming our homes. A man exhales, during
repose, not less than one-half cubic foot of carbonic acid
per hour. One gas-burner liberates five cubic feet in the

32. Carbonic acid in volcanic regions ? In Java? At Lake Avernus ? In mines?

33. In the open air? Amount of carbonic acid exhaled by a man? A gas-
burner ? A room fire ? From furnaces ?

RESPIRATION. 139

same time, and spoils about as much air as ten men. A
fire burning in a grate or stove emits some gaseous impur-
ity, and at the same time abstracts from the air as much
oxygen as twelve men would consume in the same period,
thus increasing the relative amount of carbonic acid in
the air. From furnaces, as ordinarily constructed, this gas,
with other products of combustion, is constantly leaking
and vitiating the air of tightly-closed apartments.

34. Effects of Impure Air. — Carbonic acid, in its
pure form, is irrespirable, causing rapid death by suffoca-
tion. Air containing forty parts per thousand of this gas
(the composition of the expired breath) extinguishes a
lighted candle, and is fatal to birds ; when containing one
hundred parts, it no longer yields oxygen to man and
other warm-blooded animals; and is of course at once
fatal to them. In smaller quantities, this gas causes head-
ache, labored respiration, palpitation, unconsciousness, and
convulsions. ,

35. In crowded and badly ventilated apartments, where
the atmosphere relatively contains from six to ten times
the natural amount of carbonic acid, the contaminated air
causes dulness, drowsiness, and faintness; the dark, im-
pure blood circulating through the brain, oppressing that
organ and causing it to act like a blunted tool. This is a
condition not uncommon in our schools, churches, court-
rooms, and the like, the places of all others where it is
desirable that the mind should be alert and free to act;
but, unhappily, an unseen physiological cause is at work,
dispensing weariness and stupor over juries, audience, and
pupils.

36. Another unmistakable result of living in and breath-
ing foul air is found in certain diseases of the lungs,
especially consumption. For many years the barracks of

34. Effects of inhaling carbonic acid alone ? In email quantities?

35. Effects of the air in crowded and badly ventilated rooms?

36. A cause of consumption ? How was the fact illustrated ?

140 RESPIRATION.

the British army were constructed without any regard to
ventilation; and during those years the statistics showed
that consumption was the cause of a very large proportion
of deaths. At last the government began to improve the
condition of the buildings, giving larger space and air-
supply; and as a consequence, the mortality from con-
sumption has diminished more than one-third.

37. The lower animals confined in the impure atmos-
phere of menageries, contract the same diseases as man.
Those brought from a tropical climate, and requiring arti-
ficial warmth, generally die of consumption. In the Zoo-
logical gardens of Paris, this disease affected nearly all
monkeys, until care was taken to introduce fresh air by
ventilation; and then it almost wholly disappeared. The
tendency of certain occupations to shorten life is well
known; disease being occasioned by the fumes and dust
which arise from the material employed, in addition to the
unhealthful condition of the workshop or factory where
many hours are passed daily.

38. The following table shows the comparative amount
of carbonic acid in the air under different conditions and
the effects sometimes produced: —

PROPORTION OP CARBONIC ACID. in 1000 parts of Air.

Air of country .4

" "city 5

In hospital, well ventilated 6

In school, church, etc., fairly ventilated 1.2 to 2.5

In court-house, factory, etc., without ventilation. ... 4. to 40.

In bedroom, before being aired 4.5

In bedroom, after being aired 1.5

Constantly breathed, causing ill health 2.

Occasionally breathed, causing discomfort 3.

Occasionally breathed, causing distress 10.

Expired air 40.

Air no longer yielding oxygen 100.

37. How, in the case of the lower animals* ? Tendency of certain occupations ?

38. Give the fact as set forth in the table.

RESPIRATION. 141

39. Nature's Provision for Purifying the Air. —

We have seen that carbonic acid is heavier than air, and
is poisonous. Why, then, does it not sink upon and over-
whelm mankind with a silent, invisible wave of death ?
Among the gases there is a more potent force than gravity,
which forever precludes such a tragedy. It is known as
the diffusive power of gases. It acts according to a defi-
nite law, and with a resistless energy compelling these
gases, when in contact, to mingle until they are thor-
oughly diffused. The added influence of the winds is
useful, by insuring more rapid changes in the air; air in
motion being perfectly wholesome. The rains also wash
the air.

40. We have seen that the whole animal creation is con-
stantly abstracting oxygen from the atmosphere, and as
constantly adding to it vast volumes of a gas injurious alike
to all, even in small quantities. How, then, does the air re-
tain, unchanged, its life-giving properties ? The constant
purity of the air is secured by means of the vegetable cre-
ation. Carbonic acid is the food of the plants, and oxygen
is its waste product. The leaves are its lungs, and under
the stimulus of sunlight a vegetable respiration is set in
motion, the effects of which are just the reverse of the
function we have been considering. Thus nature purifies
the air, and at the same time builds up beautiful and use-
ful forms of life from elements of decay.

41. In the sea, as in the air, the same circle of changes
is observed. Marine animals consume oxygen and give off
carbonic acid; while marine plants consume carbonic acid
and liberate oxygen. Taking advantage of this fact, we
may so arrange aquaria with fishes and sea-plants, in their
proper combinations, so that each supplies the needs of the
other, and the water requires seldom to be renewed. This

39. What can you state of the diffusive power of gases ? The added influence
of the winds ?

40. How is the constant purity of the air secured ? Explain the process ?

41. What process occurs in the sea J How is the fact illustrated ?

142 RESPIRATION.

affords us, on a small scale, an illustration of the mutual
dependence of the two great kingdoms of nature; as well
as of those compensating changes which are taking place
on such a grand scale in the world about us.

42. Ventilation. — Since the external atmosphere, as
provided by nature, is always pure, and since the air in our
dwellings and other buildings is almost always impure, it
becomes imperative that there should be a free communica-
tion from the one to the other. This we aim to accomplish
by ventilation. As our houses are ordinarily constructed,
the theory of ventilation, "to make the internal as pure as
the external air," is seldom carried out. Doors, windows,
and flues, the natural means of replenishing the air, are
too often closed, almost hermetically, against the precious
element. Special means, or special attention, must there-
fore be used to secure even a fair supply of fresh air. This
is still more true of those places of public resort, where
many persons are crowded together.

43. If there are two openings in a room, one as a vent
for foul air, and the other an inlet for atmospheric air,
and if the openings be large, in proportion to the number
of air consumers, the principal object will be attained.
Thus, a door and window, each opening into the outer air,
will ordinarily ventilate a small apartment; or a window
alone will answer, if it be open both above and below, and
the open space at each end be not less than one inch for
each occupant of the room, when the window is about a
yard wide. The direction of the current is generally from
below upward, since the foul, heated air tends to rise;
but this is not essential. Its rate need not be rapid ; a
" draught," or perceptible current, is never necessary to
good ventilation. The temperature of the air admitted
may be warm or cold. It is thought by many that if the

42. Character of the external air? Of the air in our dwellings ? What becomes
imperative ? Imperfect ventilation of our dwellings ?

43. What hints are given for the ventilation of our dwellings?

RESPIRATION. 143

air is cold, it is pure ; but this is an error, since cold air
will receive and retain the same impurities as warm air.

44. Shall we open our bedrooms to the night air ? Flor-
ence Nightingale says, in effect, that night air is the only
air that we can then breathe. "The choice is between pure
air without and impure air within. Most people prefer the
latter, — an unaccountable choice. An open window, most
nights in the year, can hurt no one. In great cities, night
air is the best and purest to be had in twenty-four hours.
I could better understand, in towns, shutting the windows
during the day than during the night."

45. Animal Heat. — Intimately connected with respi-
ration is the production of animal heat, or the power of
maintaining the temperature of the body above that of the
medium in which the creature moves; thus, the bird is
warmer than the air, and the fish than the water. This
elevation of temperature is a result of the various chemi-
cal changes which are constantly taking place in the system.
Although common to all animals, in a greater or less
degree, heat is not peculiar to them ; since plants also gen-
erate it, especially at the time of sprouting and flowering.
If a thermometer be placed in a cluster of geranium flow-
ers, it will indicate a temperature several degrees above
that of the surrounding air.

46. Among animals great differences are noticed in this
respect, but the degree of heat produced is always propor-
tional to the activity of respiration and the amount of
oxygen consumed. Accordingly, the birds, whose habits
are extremely active, and whose breathing capacity is the
greatest, have uniformly the highest temperature. Slug-
gish animals, on the contrary, as frogs, lizards, and snakes,
have little need for oxygen, and have incompletely de-

44. State what Florence Nightingale says about inhaling night air?

45. Warmth of the bird as compared with that of the air? Of the fish and
the water ? Heat in animals and plants ? How illustrated with the thermometer ?

46. Amount of heat in animals, how apportioned? As regards the birds?
Frogs, and other sluggish animals ? Arrangement made by zooligsts ?

144 RESPIRATION.

veloped lungs ; these animals are cold to the touch, that is,
they have relatively a lower temperature than man, and
their positive temperature is but little above that of the
external air. Accordingly, zoologists have so arranged the
animal kingdom that warm-Hooded animals, including
man, the Ijff ds, and the quadrupeds, are classified together ;
while the cold-blooded animals, such as the fish, tortoise,
frog, and all that have no vertebral column, are classed
by themselves.

47. The temperature of the human body is about 100°
Fahrenheit, and remains about the same through winter
and summer, in the tropics as well as in the frozen regions
of the north. It may change temporarily within the range
of about twelve degrees; but any considerable, or long-con-
tinued elevation or diminution of the bodily heat is certain
to result disastrously.

48. Man is able to adapt himself to all extremes of
climate; and, in fact, by means of clothing, shelter, and
food, is able to create for himself an artificial climate where-
ever he choses to reside. The power to resist cold consists
chiefly in preventing the heat which is generated by the
vital processes of the body from being lost by radiation.
Warm clothing, such as we wear in winter, has, in reality,
the same temperature as that which is worn in summer ;
but, by reason of being thick and porous, it is a bad con-
ductor of heat, and thus prevents the escape of that
produced by the body. If woollen fabrics were intrinsically
warm, no one would wrap a piece of flannel, or blanket,
around a block of ice to prevent its melting in summer.

49. The faculty of generating heat explains how it is
that we are enabled to resist the effects of cold; but how
does the body withstand a temperature higher than its

47. State what is said respecting the temperature of the human body.

48 1 Ability of man to adapt himself to different climates ? In what does the
power to resist cold consist ? What is said about warm clothing ?

49» Men in an atmosphere above the boiling-point ? In foundries and glass
works ?

RESPIRATION. 145

own ? Men have been known to remain several minutes in
an atmosphere heated above the boiling-point of water, and
yet the temperature of their own bodies was not greatly ele-
vated. Those who labor in foundries and glass-works are
habitually subjected to very high degrees of temperature,
but they do not suffer in health more than thosie engaged
in many other occupations.

50. The regulation of the temperature of the body is
effected by means of perspiration, and by its evaporation.
So long as the skin acts freely and the air freely absorbs
the moisture, the heat of the body does not increase, for
whenever evaporation takes place, it is attended by the
abstraction of heat — that is, the part becomes relatively
colder. This may be tested by moistening some part of
the surface with cologne, ether, or other volatile liquid,
and then causing it to evaporate rapidly by fanning. The
principle that evaporation produces cold has been in-
geniously and practically employed, in the manufacture
of ice, by means of freezing machines.

51. Spontaneous Combustion. — Is it possible that
the temperature of the living body can be so increased,
that its tissues will burn spontaneously ? From time to
time, cases have been reported in which, by some mysteri-
ous means, considerable portions of the human body have
been consumed, apparently by fire, the victim being found
dead, or incapable of explaining the occurrence. Hence,
the theory has been current that, under certain condi-
tions, the tissues of the body might become self-ignited ;
and the fact that this so-called spontaneous combustion
has ordinarily taken place in those who had been addicted
to the use of alcoholic drinks, has given a color of proba-
bility to the opinion. It has been supposed that the flesh
of these unfortunate persons becoming saturated with the
inflammable properties of the alcohol thus taken into the

&O. The regulation of the temperature of the body. Give the explanation.
51) 52. State what is said of spontaneous combustion.

146 RESPIRATION.

system, took fire upon being exposed to a flame, as of a
lighted candle, or, indeed, without any external cause. But,
whether this be possible or not, one thing is certain, this
strange kind of combustion has never been actually wit-
nessed by any one competent to give a satisfactory account
of it.

52. The results that have been observed may be satis-
factorily explained by the accidental ignition of the clothes,
or other articles near the body, and by the supposition
that the individual was at the time too much stupefied by
intoxication, to notice the source of danger, and provide
for his safety. The highest temperature that has been
observed in the body, about 112° Fahrenheit, is too low
to ignite the vapor of alcohol; much less will it cause
the burning of animal tissues. It is undoubtedly true
that when the tissues are filled with alcohol, combus-
tion will more easily take place than when the body is in
a normal state ; but, under any condition, the combustion
of the body requires a higher degree of heat than can be
generated by the body itself, or the mere proximity of a
lighted candle, or any cause of a similar character.

REVIEW QUESTIONS. 147

QUESTIONS FOR TOPICAL REVIEW.

PAGE

1. What is the object of respiration ? 123

2. What are the special organs of respiration ? 123

3. In what organ? do s a change in the blood take place ? 123

4. What is the nature of the change ? 123, 133

5. Where are the lungs situated, and what is the character of the sub-

stance of which they are composed ? 123, 125

6. Describe the facilities provided for the lung movements 124

7. Describe the trachea, or windpipe. 124, 125, 127, 128

8. Describe the bronchial tubes, and their uses 125, 126

9. What can you state in relation to the epiglottis ' 1-26, 127

10. What are the cilia and what use do they probably serve ? 128

11. How may the lungs be affected by not being properly protected ? 128

12. Describe the movements necessary to the act of perfect respiration. . . 128, 129

13. What is the diaphragm, and what is its office? 128, 129

14. How may the organs of respiration be so improved as to increase their

capacity and power ? 129, 37

15. What is stated in relation to the frequency of respiration ? 129, 130

10. To what extent may the act of respiration be subjected to our wills ? 130

17. What may be said to be the capacity of the lungs ? 130, 131

18. How long does it take every particle of air in the lungs to be expelled and

new air to take its place ? 130

19. What would be the consequences, if the entire capacity of the lungs

were constantly used ? 130, 131

20. What would be the consequences to a fish put into water from which the

air had been completely exhausted ? Why ? 131

21. What is the air, and what are its parts ? 131, 136, 138

22. What, is the character of the air that has been just breathed ? 132

23. Why is it that such air is not fit for respiration ? 132, 139

24. What are the effects, as recorded in notable cases, of confinement in places

the air of which has been breathed " over an , over ?" 133

25. What can you state of changes in the blood from respiration ? . 133

26. What of the air, as an article of food ? 133, 134

27. What, on the subject of interchange of gases in the lungs ? 134

28. Explain the difference between arterial and venous blood 134, 135

29. Explain, if you can, the cau-e of the difference 135

30. State what you can in relation to blue blood 135

31 . In relation to the amount of labor exerted in respiration 135, 136

32. In relation to the deleterious properties of different gases 136, 137

33. In relation to the dust that floats in the air 137, 138

34. What are the properties of carbonic acid gas ? 132, 138, 141

35. In what places is carbonic acid gas commonly found ? 132, 138, 139

36. Describe the effects of carbonic acid gas 132, 128, 139, 141

37. What are the general effects of breathing any impure atmosphere ? . . . . 139, 140

38 What are Nature's provisions for purifying the air? 141, 142

3f». What hints and directions are given on the subject, of ventilation ?. . . . 142, 143

40. How does the temperature of the body compare with the medium in which

it lives? 143

41. How is temperature of the body regulated and sustained ? 143, 144, 145

42. State what you can on the subject of spontaneous combustion 145, 146

148 THE tfEKVOUS SYSTEM.

CHAPTER IX.
THE NERVOUS SYSTEM.

Animal and Vegetative Functions — Sensation, Motion, and Volition —
The Structure of the Nervous System — The White and Gray Sub-
stances— The Brain — Its Convolutions — The Cerebellum — The Spi-
nal Cord andf its System of Nerves— The Anterior and Posterior
Roots — The Sympathetic System of Nerves — The Properties of Nerv-
ous Tissue — Excitability of Nervous Tissues — The Functions of the
Spinal Nerves and Cord — The Direction of the Fibres of the Cord —
Reflex Activity, and its Uses— The Functions of the Medulla Oblon-
gata and the Cranial Ganglia — The Reflex Action of the Brain.

1. Animal Functions. — The vital processes which we
have been considering, in the three previous chapters, of
digestion, circulation, and respiration — belong to the class
of functions known as vegetative functions. That is, they
are common to vegetables as well as animals; for the
plant, like the animal, can originate nothing, not even
the smallest particle of matter; and yet it grows, blossoms,
and bears fruit, by reason of obtaining and digesting the
nutriment which the air and soil provide. The plant has
its circulatory fluid and channels, by which the nutriment
is distributed to all its parts. It has, also, a curious ap-
paratus in its foliage, by which it abstracts from the air
those gaseous elements so necessary to its support; and
thus it accomplishes vegetable respiration. These vege-
tative functions have their beginning and end within the
organism of the plant; and their object is the preservation
of the plant itself, as well as of the entire species.

2. The animal, in addition to these vegetative functions,
has another set of powers, by the use of which he becomes
conscious of a world external to himself, and brings him-

1. What processes are known as the vegetative functions? Why so called?
What properties and functions does the plant possess ? Their object ?

2. What second set of powers has the animal ? What functions are mentioned ':
The advantage they give ?

THE NERVOUS SYSTEM. 149

self into active relations with it. By means of the vege-
tative processes, his life and species are maintained; while,
by means of certain animal functions, he feels, acts; and
thinks. These functions, among which are sensation,
motion, and volition, not only distinguish the animal from
the plant, but, in proportion to their development, elevate
one creature above another ; and it is by virtue of his pre-
eminent endowment, in these respects, that man holds his
position at the head of the animal creation.

3. Among animals whose structure is very simple, the
hydra, or fresh- water polyp, being an example, no special
organs are empowered to perform separate functions ; but
every part is endowed alike, so that if the animal be cut
into pieces, each portion has all the properties of the entire
original; and, if the circumstances be favorable, each of
the pieces will soon become a complete hydra. As we ap-
proach man, in the scale of beings, we find that the orgaifs
multiply, and the functions become more complete. The
function of motion, the instruments of which— the muscles
and bones— have been considered in former chapters, and
all the other animal functions of man, depend upon the set
of organs known as the nervous system.

4. The Nervous System. — The intimate structure
of this system differs from any tissue which we have be-
fore examined. It is composed of a soft, pulpy substance,
which, early in life, is almost fluid, hut which gradually
hardens with the growth of the body. When examined
under the microscope, it is found to be composed of two
distinct elements: — (1) the white substance, composing
the larger proportion of the nervous organs of the body,
which is formed of delicate cylindrical filaments, about
-g-jJL- of an inch in diameter, termed the nerve-fibres ; and
(2) the gray substance, composed of grayish-red, or ashen-

3. Animals whose structure is simple? As we approach man? Dependence
of the animal functions of man ?

4. The nervous tissues, of what composed ? When examined by the aid of the
microscope ? The white substance ? The gray substance ?

150 THE NERVOUS SYSTEM.

colored cells, of various sizes, generally possessing one or
more off-shoots, which are continuous with the nerve-
fibres just mentioned.

5. The gray, cellular substance constitutes the larger
portion of those important masses, which bear the name of
nervous centres and ganglia (from ganglion, a knot), and
in which all the nerve-fibres unite. These white nerve-
fibres are found combined together in long and dense
cords, called nerves (from neuron, a cord), which serve to
connect the nervous centres with each other, and to place
them in communication with all the other parts of the
body which have sensibility or power of motion. That
part of the nervous system which is concerned in the ani-
mal functions, comprises the brain, the spinal cord, and the
nerves which are derived therefrom; these are, together,
called the cerebro-spinal system (Fig. 40) ; while that other
set of organs, which presides over, and regulates the vege-
tative functions, is called the sympathetic system of nerves.

6. The Brain. — The brain is the great volume of nerv-
ous tissue that is lodged within the skull. It is the largest
and most complex of the nervous centres, its weight, in the
adult, being about fifty ounces, or one-fortieth of that of
the whole body. The shape of the brain is oval, or egg-
shaped, with one extremity larger than the other, which is
placed posteriorly in the skull, to the concavity of which it
very closely conforms. The brain consists chiefly of two
parts; the cerebrum, or brain proper, and the cerebellum,
or "little brain." In addition to these, there are several
smaller organs at the base, among which is the commence-
ment or expansion of the spinal cord, termed the medulla
oUongata9 or oblong marrow.

7. The tissue of the brain is soft and easily altered in

5. Nervous centres and ganglia? Nerves? What do they serve? Cerebro-
epinal system?

6. Location of the brain ? Its weight ? Its shape ? Of what it consists ? What
or-ran* at the base ?

7. The tissue of the brain ? What, therefore, is required ? Blows on the head ?
Membranes of the brain ? Blood sent to the brain ?

THE NERVOUS SYSTEM.

151

FIG. 40.— THK CEREBRO-SPINAI, SYSTEM.

152 THE NERVOUS SYSTEM.

shape by pressure; it therefore requires to be placed in a
well-protected position, such as is afforded by the skull, or
cranium, which is strong without being cumbrous. In
the course of an ordinary lifetime, this bony box sustains
many blows, with little inconvenience; while', if they fell
directly upon the brain, they would at once, and com-
pletely, disorganize that structure. Within the skull, the
brain is enveloped by certain membranes, which at once
protect it from friction, and furnish it with a supply of
nutrient vessels ; they are called the arachnoid, or "spiders
web," the dura mater and the pia mater, or the "tough"
and "delicate coverings." The supply of blood sent to
the brain is very liberal, amounting to one-fifth of all
that the entire body possesses. The brain of man is
heavier than that of any other animal, except the ele-
phant and whale.

8. The Cerebrum. — The brain proper, or cerebrum, is
the largest of the intracranial organs, and occupies the en-
tire upper and front portion of the skull. It is almost com-
pletely bisected, by a fissure, or cleft, running through it
lengthwise, into two equal parts called hemispheres. The
exterior of these hemispheres is gray in color, consisting
chiefly of nerve-cells, arranged so as to form a layer of gray
matter one-fifth of an inch in thickness, and is abundantly
supplied with blood-vessels. The interior of the brain,
however, is composed almost wholly of white substance, or
nerve-fibres.

9. The surface of the cerebrum is divided by a consid-
erable number of tortuous and irregular furrows, about
an inch deep,' into "convolutions," as shown in Fig. 41.
Into these furrows the gray matter of the surface is ex-
tended, and, in this manner, its quantity is vastly in-
creased. The extent of the entire surface of the brain,

8. Size of the brain proper? How divided? The exterior of the hemispheres?
The interior ?

9. The surface of the cerebrum, how marked ? The gray matter of the surface ?
Extent of the entire brain surface ? Source of nervous power ? What further ?

THE- NERVOUS SYSTEM.

153

•with the convolutions unfolded, is'cornputed to be equal to
four square feet; and yet it is easily enclosed within the
narrow limits of the
skull. When it is
stated that the gray
matter is the' true
source of nervous
power, it becomes
evident that this
arrangement has an
important bearing
on the mental ca-
pacity of the indi-
vidual. And it is
noticed that in
children, before the
mind is brought
into vigorous use,
these markings or
furrows on the sur-
face are compara-
tively shallow and
indistinct; the same fact is true of the brain in the less
civilized races of mankind and in the lower animals. It is
also noticeable, that among animals, those are the most
capable of being educated which have the best develop-
ment of the cerebrum.

10. The Cerebellum.— The "little brain" is placed
beneath the posterior part of the cerebrum, and, like the
latter, is divided into hemispheres. Like it, also, the sur-
face of the cerebellum is composed of gray matter, and its
interior is chiefly white matter. It has, however, no con-
volutions, but is subdivided by many crescentic, parallel
ridges, which, sending down gray matter deeply into the

-II.— Ui'PKK SURFACE OF THE CEREBRUM.

A, Longitudinal Fissure.

B, The Hemispheres.

10. Location of the " little brain ?'
Its subdivisions ? Its size ?

How divided ? Its surface and interior ?

7*

154 THE NERVOUS SYSTEM.

white, central portion, gives the latter a some what branched
appearance. This peculiar appearance lias been called

FIG. 42.— VERTICAL SECTION OF THE BRAIN.

A, Left Hemisphere of Cerebrum. D, The Pons Varolii.

B, Corpus Callosum. E, Upper extremity of the Spinal Cora,

C, Optic Thalamup. F, The Arbor Vitae.

the arbor vitce, or the " tree of life," from the fact that
when a section of the organ is made, it bears some resem-
blance to the trunk and branches of a tree (Fig. 42, F).
In size, this cerebellum, or "little brain," is less than one-
eighth of the cerebrum.

11. From the under surface of the cerebrum, and from
the front margin of the cerebellum, fibres collect together
to form the medulla oUongata (Fig. 43, MA), which, on is-
suing from the skull, enters the spinal column, and then
becomes known as the spinal cord. From the base of the
brain, and from the sides of the medulla originate, also,
the cranial nerves, of which there are twelve pairs. These
nerves are round cords of glistening white appearance, and,

4

11. Medulla oblongata? Cranial nerves? Their shape and position ?

THE NERVOUS SYSTEM. 155

like the arteries, generally lie remote from the surface of
the body, and are well protected from injury.

FIG. 13.— THE BASE OF THE BRAIN.

12. The Spinal Cord. — The spinal cord, or "marrow,"
is a cylindrical mass of soft nervous tissue, which occupies
a chamber, or tunnel, fashioned for it in the spinal column
(Fig. 44). It is composed of the same substances as the
brain ; but the arrangement is exactly reversed, the white
matter encompassing or surrounding the gray matter in-
stead of being encompassed by it. The amount of the
white substance is also greatly in excess of the other ma-
terial. A vertical fissure partly separates the cord into
•two lateral halves, and each half is composed of two sep-
arate bundles of fibres, which are named the anterior and
posterior columns.

13. These columns have entirelv different uses, and each

12. The spinal cord ? Of what composed ? How divided ? Each half?

13. Uses of these columns ? Importance of this part of the nervous system ?
How protected?

15G

THE NERVOUS SYSTEM.

FIG. 44.

A, Cerebrum.

B, Cerebellum.

D, D. Spinal Cord.

of them unites with a different
portion of the nerves which have
their origin in the spinal cord.
The importance of this part of
the nervous system is apparent
from the extreme care taken to
protect it from external injury.
For, while a very slight disturb-
ance of its structure suffices to
disarm it of its power, yet so
staunch is its bony enclosure,
that only by very severe injuries
is it put in peril. The three
membranes that cover the brain
are continued downward so as
to envelope and still further
shield this delicate organism.

14. The Spinal Nerves.—
The spinal- nerves, thirty- one
pairs in number, spring from
each side of the cord by two
roots, an anterior and a poste-
rior root, which have the same
functions as the columns bear-
ing similar names. The poste-
rior root is distinguished by pos-
sessing a ganglion of gray mat-
ter, and by a somewhat larger
size. The successive points of
departure, or the oif-shooting of
these nerves, occur at short and
nearly regular intervals along
the course of the spinal cord.
Soon after leaving these points,

14. The spinal nerves? The posterior root? The nerves, how arranged:
"heir office ?

THE NERVOUS SYSTEM. 157

the anterior and posterior roots unite to form the trunk
of a nerve, which is distributed, by means of branches,
to the various organs of that part of the body which this
nerve is designed to serve. The spinal nerves supply
chiefly the muscles of the trunk and limbs and the ex-
ternal surface of the body.

15. The tissue composing the nerves is entirely of the
white variety, or, in other words, the nerve-fibres ; the
same as we have observed forming a part of the brain.
But the nerves, instead of being soft and pulpy, as in the
case of the brain, are dense in structure, being hardened
and strengthened by means of a fibrous tissue which sur-
rounds each of these delicate fibres, and binds them to-
gether in glistening, silvery bundles. Delicate and mi-
nutely fine as are these nerve-fibres, it is probable that
each of them pursues an unbroken, isolated course, from its
origin, in the brain or elsewhere, to that particular point
which it is intended to serve. For, although their extrem-
ities are often only a hair's breadth distant from each other,
the impression which any one of them communicates is
perfectly distinct, and is referred to the exact point whence
it came.

16. This may be illustrated in a simple manner, thus:
if two fingers be pressed closely together, and the point of a
pin be carried lightly across from one to the other, the eyes
may be closed, and yet we can easily note the precise instant
when the pin passes from one finger to the other. If the
nerve-fibres were less independent, and if it were necessary
that they should blend with and support each other, all
accuracy of perception would be lost, and all information
thus afforded would be pointless and confused. These sil-
very threads must, therefore, be spun out with an infinite
degree of nicety. Imagine, for instance, the fibre which

1 5. The nerve tissue ? Its character ? Course of each nerve fibre ?

1 6. How may we illustrate the fact ? The fibre connecting the brain with a
point in the foot ?

158 THE NERVOUS SYSTEM.

connects the brain with some point on the foot, — its length
cannot be less than one hundred thousand times greater
than its diameter; and yet it performs its work with as
much precision as fibres that are comparatively much
stronger and less exposed.

17. The Sympathetic System. — The sympathetic
system, of nerves remains to be described. It consists of a
double chain of ganglia, situated on each side of the
spinal column, and extending through the cavities of the
trunk, and along the neck into the head. These ganglia
are made up for the most part of small collections of gray
nerve-cells, and are the nerve-centres of this system.
From these, numerous small nerves are derived, which
connect the ganglia together, send out branches to the
cranial and spinal nerves, and form networks in the vicin-
ity of the stomach and other large organs. A considerable
portion of them also follows the distribution of the large
and small blood-vessels, in which the muscular tunic ap-
pears. Branches also ascend into the head, and supply
the muscles of the eye and ear, and other organs of sense.

18. In this manner, the various regions of the body are
associated with each other by a nervous apparatus, which
is only indirectly connected with the brain and spinal
cord; and thus it is arranged that the. most widely sep-
arated organs of the body are brought into close and
active sympathy with each other, so that, "if one member
suffers, all the other members suffer with it." From this
fact, the name sympathetic system, or the great sympathetic
nerve, has been given to the complicated apparatus we have
briefly described. Blushing and pallor are caused by men-
tal emotions, as modesty and fear, which produce opposite
conditions of the capillaries of the face by means of these
sympathetic nerves.

1 7. The sympathetic system of nerves ? Of what does it consist ?

18. Association of the various regions of the body ? If one member suffers ?
Blushing *

THE XERVOUS SYSTEM. 159

19. The Properties of Nervous Tissue.— We have
seen that in all parts of this system, there are only two
forms of nervous tissue; namely,. the gray substance and
the white substance, so called from their difference of color
as seen by the naked eye; or the nerve-cell, and the nerve-
fibre, so called from their microscopic appearance. Now
these two tissues are not commonly mingled together, but
either form separate organs, or distinct parts of the same
organs. This leads us to the conclusion that their respec-
tive uses are distinct. And this proves to be the simple
fact; wherever we find the gray substance, we must look
upon it as performing an active part in the system, that is,,
it originates nervous impulses ; the white matter, on the
contrary, is a passive agent, and serves merely as a con-
ductor of nervous influences. Accordingly, the nervous
centres, composed so largely of the gray cells, are the great
centres of power, and the white fibres are simply the in-
struments by which the former communicate with the near
and distant regions of the body under their control.

20. We may compare the brain, then, to the capital, or
seat of government, while the various ganglia, including
the gray matter of the cord, like so many subordinate
official posts, are invested with authority over the outly-
ing provinces; and the nerves, with the white matter of
the cord, are the highways over which messages go and
return between these provinces and the local or central
governments. But both forms of nervous tissue possess
the same vital property, called excitability ; by which term
is meant, that when a nerve-cell or fibre is stimulated by
some external agent, it is capable of receiving an impres-
sion and of being by it excited into activity. A ray of
light, for example, falling upon one extremity of a fibre
ill the eye, excites it throughout its whole length ; and its

1 9. Properties of nervous tissue ? Office of the gray substance ? Of the white ?
"he nervous centres? White fibres ?

20. What comparison is made between the brain and the nation's capitol ?
The vital property, excitability ? What example is given ?

160 THE NERVOUS SYSTEM.

other extremity, within the brain, communicating with a
nerve-cell, the latter, in its turn, is excited, and the sensa-
tion of sight is produced.

21. What sort of change takes place in the nervous
tissue when its excitability is aroused, is not known ;
certainly none is visible. On this account, it has been
thought by some, that the nerve-fibre acts after the man-
ner of a telegraph wire : that is, it transmits its messages
without undergoing any material change of form. But,
though the comparison is a convenient one, it is far from
being strictly applicable ; and the notion that nerve-force
is identical with electricity has been fully proved to be
incorrect.

22. The Functions of the Nerves. — The nerves
are the instruments of the two grand functions of the
nervous system, Sensation and Motion. They are not the
true centres of either function, but they are the conductors
of influences which occasion both. If the nerve in a limb
of a living animal be laid bare, and irritated by pinching,
galvanizing, or the like, two results follow, namely: the
animal experiences a sensation, that of pain, in the part to
which the nerve is distributed, and the limb is thrown into
convulsive action. WJien a nerve in a human body is cut
by accident, or destroyed by disease, the part in which it
ramifies loses both sensation and power of motion ; or, in
other words, it is paralyzed. We accordingly say that the
nerves have a twofold use, a sensory and motor function.

23. If a nerve that has been exposed be divided, and the
inner end, or that still in connection with the nerve-cen-
tres, be irritated, sensation is produced, but no movement
takes place. But if the outer end, or that still connected
with the limb, be irritated, then no pain is felt, but mus-

*v

21 • Change in the nervous tissues ? Nerve force and electricity ?

22. Functions of the nerves ? In the case of the nerve of a living animal ? Of
the human body ?

23, If an exposed nerve be divided? What is proved? The course of the sensory
set of fibres ? Of the motor set ? To what are they likened ?

THE NERVOUS SYSTEM. 161,

cular contractions are produced. Thus we prove that there
are two distinct sets of fibres in the nerves ; one of which,
the sensory fibres, conduct toward the brain, and another,
the motor fibres, conduct to the muscles. The former may
be said to begin in the skin and other organs, and end in
the brain ; while the latter begin in the nervous centres
and end in the muscles. They are like a double line of
telegraph wires, one for inquiries, the other for responses.

24. We have already spoken of the two roots of the spinal
nerves, called from their points of origin in the spinal
cord, the anterior and posterior roots. These have been
separately cut and irritated in the living animal, and it has
been found that the posterior root contains only sensory
fibres, and the anterior root has only motor fibres. So that
the nerves of a limb may be injured in such a way that it
will retain power of motion and yet lose sensation ; or the
reverse condition, feeling without motion, may exist. Be-
tween these two sorts of fibres, no difference of structure
can be found ; and where they have joined to form a nerve
it is impossible to distinguish one sort from the other.

25. Occasionally a nerve is so compressed as to be tem-
porarily unable to perform its functions : a transient par-
alysis then takes place. This is the case when the leg or
arm "gets asleep," as it is expressed. When such is the
condition with the leg, and the person suddenly attempts
to walk, he is liable to fall, inasmuch as the , motor fibres
cannot convey orders to the muscles of the limb. Another
fact is observed : there is no sensation in this nerve at the
point of its compression ; but the whole limb is numb, and
tingling sensations are felt in the foot, the point from
which the sensory fibres arise.

26. This illustrates the manner in which the brain in-

24. The two roots of the spinal nerves ? What has been found ? Difference
of the two sorts of fibres ? Result of their union ?

25. Transient paralysis ? When such is the case with the leg? What other
fact i e observed ?

26. What does this illustrate ? Sensation ? The feeling after a limb has been
amputated ? Striking of the u funny bone ?"

162 THE NERVOUS SYSTEM.

terprets all injuries of the trunk of a nerve. Sensation or
pain is not felt at the point of injury, but is referred to the
outer extremities of the nerve, where impressions are habit-
ually received. This is the reason why, after a limb has
been amputated by the surgeon, the patient appears to
suffer pain in the member that has been severed from the
body ; while some form of irritation at the end of the nerve
in the wound, or stump, is the real source of his distress.
Again, when the "funny-bone" — that is, the ulnar nerve
at the elbow, — is accidentally struck, the tingling sensa-
tions thus produced are referred to the outer side of the
hand and the little finger, the parts to which that nerve is
distributed.

27. All the spinal nerves, and two from the brain, are
concerned in both sensation and motion. Of the remainder
of the cranial nerves, some are exclusively motor, others
exclusively sensory; and still others convey, not ordinary
sensations, but special impressions, such as sight, hearing,
and smell, which we have yet to consider. However much
the functions of the nerves seem to vary, there is but little
difference discoverable in the nerves themselves, when ex-
amined under the microscope. Whatever difference exists
must be. accounted for in consequence of the nerves com-
municating with different portions of the gray matter of
•the brain. The rate of motion of a message, to or from
the brain along a nerve, has been measured by experi-
ment upon the lower animals, and estimated in the case of
man at about two hundred feet per second. As compared
with that of electricity, this is a very slow rate, but, in
respect to the size of the human body, it is practically in-
stantaneous.

28. The Functions of the Spinal Cord.— As the

27. The ppinal nerves, and two from the brain ? Of the remainder? Difference
in the nerves ? How accounted for ? The rate of conduction along a nerve ? As
compared with electricity?

28. Function!* of the anterior and posterior column? of the cord ? If the cord
be divided ?

THE NERVOUS SYSTEM. 163

anterior and posterior roots of the spinal nerves have sepa-
rate functions, so the anterior and posterior columns of
the cord are distinct in function. The former are con-
cerned in the production of motion, the latter in sensation.
If the cord be divided, as before in the case of the nerve, it
is found that the parts below the point of injury are de-
prived of sensation and of the power of voluntary motion
on both sides of the body, a form of paralysis which is
called paraplegia.

29. This form of disease, paraplegia, is sometimes seen
among men, generally as the result of a fall, or some other
severe accident, by which the bones of the spine are broken,
and the cord is crushed, or pierced by fragments of bone.
The parts which are supplied by nerves from the cord
above the point of injury are as sensitive and mobile as
before. The results are similar, whether the division hap-
pens at a higher or lower portion of the spinal cord ; but
the danger to life increases proportionally as the injury
approaches the brain. When it occurs in the -neck, the
muscles of inspiration are paralyzed, since they are sup-
plied by nerves issuing from that region ; and as a result
of this paralysis, the lungs are unable to act, and life is
speedily brought to a close.

30. When the spinal cord of an animal has been cut, in
experiment, it may be irritated in a manner similar to that
alluded to when considering the nerves. If, then, the
upper cut surface be excited, it is found that pain, refer-
able to the parts below the cut, is produced ; but when the
lower cut surface is irritated, no feeling is manifested. So
we conclude that in respect to sensation, the spinal cord is
not its true centre, but that it is merely a conductor, and
is therefore the great sensory nerve of the body. When
the lower surface of the cut is irritated, the muscles of the

29. Paraplegia? Result and danger to life? When the injury occurs in the
neck?

30. Experiment of cutting the spinal cord ot an animal ? What inference is
drawn?

164 THE NERVOUS SYSTEM.

parts below the section are violently contracted. Hence,
we conclude that, in respect to the movements ordered by
the will, the spinal cord is not their source; but that it
acts only as a conductor, and is, accordingly, the great
motor nerve of the body.

31. Direction of the Fibres of the Cord.— If one
lateral half of the spinal cord be cut, or injured, a very sin-
gular fact is observed. All voluntary power over the mus-
cles of the corresponding half of the body is lost, but the
sensibility of that side remains undiminished. This result
seems to show that the motor fibres of the cord pursue a
direct course, while its sensory fibres are bent from their
course. And this has been proved to be the fact; for im-
mediately after the posterior roots — the conductors of sen-
sory impressions — join the posterior columns, they enter
the gray matter of the cord, and passing over, ascend to the
brain on the opposite side. Accordingly, the sensory fibres
from the right and left sides interlace each other in the
gray matter ; this arrangement has been termed the decus-
sation, or crossing of these fibres. This condition serves
to explain how a disease or injury of the cord may cause a
paralysis of motion in one leg, and a loss of sensation in
the other.

32. The direction of the anterior, or motor columns of
the cord, is downward from the brain. In the cord itself,
the course of the motor fibres is for the most part, a direct
one ; but in the medulla oblongata, or upper extremity of
the cord, and therefore early in their career, these fibres
decussate, or cross from side to side in a mass ; and not
separately, as in the case of the posterior fibres just men-
tioned. This arrangement is termed the decussation of
the anterior columns of the medulla.

33. From this double interlacing of fibres results a

3 1 . What singular fact is noticed ? What doe? the result show ?

32. Direction of the anterior or motor columns? In the cord itself? In the
medulla oblongata ? The decussation ?

33. Result of the double interlacing of fibres? Where is the seat of pain

THE NERVOUS SYSTEM. 165

crossed action between the original and terminal extremity
of all nerve-fibres which pass through the medulla ;
namely, those of all the spinal nerves. Consequently, if
the right hand be hurt, the left side of the brain feels the
pain ; and if the left foot move, it is the right hemisphere
which dictates its movement. For the same reason, when
a loss of sensation and power of motion aifecting the right
side of the body alone is observed, the physiologist under-
stands that the brain has been invaded by disease upon its
left side. This affection is termed hemiplegia, or the " half-
stroke." The full-stroke, which often follows the rupture of
a blood-vessel in the brain, is commonly called paralysis.

34. The Reflex Action of the Cord. — We have
already considered the cord as the great motor and sensory
nerve of the body, but it has another and extremely impor-
tant use. By virtue of the gray matter, which occupies
its central portion, it plays the part of an independent
nerve centre. The spinal cord not only conducts some
impressions to the brain, but it also arrests others; and, as
it is expressed, " reflects" them into movements by its own
power. This mode of nervous activity is denominated the
Reflex Action of the cord.

35. A familiar example of this power of the cord is
found in the violent movements which agitate a fowl
after its head has been cut off. The cold-blooded animals
also exhibit reflex movements in an astonishing degree.
A decapitated centipede will run rapidly forward, and will
seemingly strive to overturn, or else climb over obstacles
placed in its way. A frog similarly mutilated will sustain
its headless body upon its feet, in the standing posture,
just as it might do if it were still alive. If pushed over,
it will regain its feet ; and if the feet are irritated, it will

when the right hand is hurt ? The moving of the foot ? Loss of sensation in one
side of the body ?

34. What other important use has the cord? What is the activity denomi
nated ?

35. Example of the fowl ? Centipede ? Prog ? What dc they prove ?

166 THE NERVOUS SYSTEM.

jump forward. There can be no doubt that, in the lower
animals, movements may take place which are completely
divorced from the will, sensation, and consciousness; for
in those animals, as well as in man, these faculties have
Iheir principal seat within the brain.

36. An irritation is necessary, in most instances, to
awaken reflex movements. In the case of the decapitated
fowl, its muscles are excited to convulsive action by
reason of its being thrown upon the hard ground and
roughly handled. Let it be treated differently, and the
convulsions will not take place : let it be laid gently upon
soft cotton, and the body will remain comparatively quiet.
It may comfort some people to know that the convulsions
which follow decapitation are not attended with pain ; nor
are they a necessary part of the " act of death," as some
suppose.

37. In the human body, likewise, actions are excited
that are entirely distinct from the ordinary voluntary
efforts. It is not permissible, desirable, nor even necessary
to decapitate a man that the body may be disconnected
from his brain, in order to test the effect of irritation upon
the spinal cord; although the bodies of beheaded crimi-
nals have been experimented upon, and caused to move by
powerful galvanic batteries. The resort to such means of
experiment is rendered unnecessary by the occurrence of
certain deplorable cases of disease and injury, which effect-
ually sever all communication between the brain and a
large part of the body.

38. Thus, the cord may be so far injured, as the result
of accident, as to terminate all sensation and voluntary
motion in the lower half of the body, the patient seem-
ingly becoming lifeless and powerless from the waist down-
ward. And yet, by tickling or pinching either foot, the leg

36. What i? necessary in most cases to awaken reflex movements? In tha
case of the fowl ? Convulsions which follow decapitation ?

37. Actions in the human body distinct from voluntary efforts?

38. Reflex action after injury'of the cord ? Why not'due to the muscles ?

THE NERVOUS SYSTEM. 167

of the same side may be made to jerk, or even to kick with
considerable force ; but, unless the patient is observing his
limbs, he is wholly unconscious of these movements, which
are, therefore, performed independently of the brain. And
they are in nowise due to the muscles of the limb; for,
if the cord itself becomes diseased below the point of in-
jury, the muscles cease to contract.

39. For the production of this form of nervous action
three things are requisite — (1) a nerve to conduct messa-
ges from the surface of the body, one of that variety for-
merly described as sensory, but which are now incapable of
awakening sensation ; (2) a portion of uninjured spinal
cord which shall reflect or convert impressions into im-
pulses ; and (3) a motor nerve to conduct impulses outward
to the muscles. The power of the cord to enforce reflex
acts resides in the gray matter, into which the reflex nerves
enter and from which they depart, by means of their pos-
terior and anterior roots respectively.

40. The Uses of the Reflex Action.— The reflex
activity of the cord is exhibited in the healthy body in
many ways, but since it is never accompanied with sensa-
tion, we do not readily recognize it in our own bodies.
Reflex movements are best studied in the cases of other
persons, when the conditions enable us to distinguish
between acts that are consciously, and those that are un-
consciously performed. For example, if the foot of a per-
son soundly, asleep be tickled or pinched, it will be quickly
withdrawn from the irritation.

41. Similar movements may be observed in cases where
the consciousness and sensation are temporarily obliter-
ated by disease, or by means of narcotic poisons. If the
arm of a person who has been rendered insensible by

39. What arc lh" requisites for the production of this form of nervous action?

40. Whv rlo we not readily recognize the reflex activity of the cord in our own
bodies ? How best studied in others ? Example ?

4 1 . Similar movements ? Arm of a oersou ? Melted wax or heated coin on the
hand?

168 THE NERVOUS SYSTEM.

chloroform, be raised, and then allowed to fall, it will be
noticed that the limb does not drop instantly, like a life-
less member, but a certain amount of rigidity remains -in
its muscles, which resists or breaks the force of its descent.
Again, when a substance like melted sealing-wax, or a
heated coin, falls upon the hand, the limb is snatched
away at once, even before the feeling of pain has been
recognized by the brain. When jolted in a rapidly moving
car, we involuntarily step forward or backward, so as to
preserve the centre of gravity of the body.

42. These and similar acts are executed by the same
mechanism as that previously described in the case of
paralysis from an injury of the spinal cord. The muscles
thus called into play, are those which are ordinarily under
the sway of the will, but which in these cases act through
this reflex action of the cord, altogether independently of
the will. A healthful reflex activity produces an elasticity,
or " tone," of the voluntary muscular system, which, in a
great measure, explains the existence in the young and
vigorous of a feeling of buoyancy and reserve power. Its
possessor is restlessly active, and it may appropriately be
said of him, "he rejoiceth as a strong man to run a race."
But this reflex energy may be deficient. This is true when
the blood is poor and wanting in its solid ingredients, or
the circulation is feeble ; the muscles, then, are flabby and
weak, and the person himself is said to be " nerveless," or
indisposed to exertion. Shivering from cold, and trem-
bling from fear, may, in part, be referred to a temporary
loss of tone, resulting from a powerful impression upon the
brain-

43. An excess of this activity may also be observed in
disease. In this condition, the excitability of the cord is
unnaturally aroused, and frequent and violent movements

42. Result of healthful reflex activity ? When may the reflex energy he defl-

43. Excess of this activity in disease ? Hydrophobia, etc. ? The difference in
severity of the convulsions0 "

THE NERVOUS SYSTEM. 169

of the limbs and body, called convulsions, are the result.
The convulsions of young children, and the nervous agita-
tion of chorea, or St. Vitus's dance, are reilex in character;
ag are also the symptoms attending poisoning by strychnine,
and those terrible diseases, tetanus, or " locked jaw," and
hydrophobia. The severity of the convulsions is not the
same in all cases of these disorders ; but. in those last men-
tioned the most violent spasmodic movements are provoked
by the slightest form of irritation — such as the sound of
pouring water, the sight of any glittering object, the glanc-
ing of a mirror, the contact of cool air, or even the touch
of the bedclothes.

44. Another variety of reflex motions takes place in cer-
tain involuntary muscles, and over these the cord exercises
supreme control. They are principally those movements
which aid the performance of digestion and nutrition, the
valve-action of the pylorus, and other movements of the
stomach and intestines. In these movements the mind
shares no part. And it is well that this is so ; for since
the mind is largely occupied with affairs external to the
body, it acts irregularly, becomes fatigued, and needs fre-
quent rest. The spinal cord, on the contrary, is well fitted
for the form of work on which depends the growth and
support of the body, as it acts uniformly, and with a ma-
chine-like regularity.

45. These operations are not accompanied by conscious-
ness ; for, als a general rule, the attention is only called to
them when they become disordered. Many a person does
not know where his stomach is situated, until he discovers
its position by reason of a feeling of distress within it,
produced by giving that organ improper work to perform.
In this manner the higher and nobler faculties of the
mind are liberated from the simply routine duties of the

44. Another variety of reflex motions ? What are they ? What is stated of the
mind in connection with these movements ?

45. Consciousness in these operations? Physical wants ?

8

170 THE NERVOUS SYSTEM.

body; and we are thus left to direct the attention, the rea-
son, and the will to the accomplishment of the great ends
of our existence. If it were otherwise, wre could only find
time to attend to our ordinary physical wants.

46. The objects of the reflex activity of the cord are
threefold. In the first place, it acts as the protector of man,
in his unconscious moments. It is his unseen guardian,
always ready to act, never growing weary, and never re-
quiring sleep. Nor does its faithful action wholly cease
with the cessation of life in other parts. In the second
place, it is the regulator of numerous involuntary motions
that are necessary to the nutrition of the body. Here its
actions are entirely independent of the brain, and are per-
formed in a secret and automatic manner. And. thirdly, it
acts as a substitute, and regulates involuntary movements
in the muscles usually under the influence of the will. It
thus takes the place of the higher faculties in performing
habitual acts, and permits them to extend their operations
more and more beyond the body and its material wants.

47. The Functions of the Medulla Oblongata.
—The prolongation of the spinal cord, within the skull,

has been previously spoken of as the medulla oblongata.
It resembles the cord, in being composed of both white
and gray matter, and in conducting sensory and motor in-
fluences. It likewise gives rise to certain nerves, which are
here called cranial nerves (from cranium, the skull). All
except two of these important nerves spring from the me-
dulla, or the parts immediately adjoining it ; the exceptions
are the two nerves taking part in the special senses of sight
and smell, which nerves have their origin at the base of
the cerebrum.

48. The decussation, or crossing of the motor columns,
has been previously described, when treating of the direc-

46. How many objects may the reflex activity be said to have ? State the first.
The second. The third.

47. How does the medulla oblongata resemble the cord ?

48. What final fact is observed in the crossing of the motor columns ?

THE NERVOUS SYSTEM. 1?1

tion of the nerve-fibres of the cord ; and the singular fact
has been alluded to, that when one side of the brain is
injured, its effects are limited to the opposite side of the
body. One more fact remains to be observed in this con-
nection, namely, this crossed action does not usually take
place in the cranial nerves. Accordingly, when apoplexy,
or the rupture of a blood-vessel, occurs in the right hemi-
sphere of the cerebrum, the left side of the body is paralyzed,
but the right side of the face is affected; this is because
that part of the body is supplied by the cranial nerves.

49. A portion of the medulla presides over the impor-
tant function of respiration, and from it arises the pneu~
mogastric nerve, so called because its branches serve both
the lungs and stomach. The feelings of hunger, thirst,
and the desire for air are aroused by means of this nerve.
The wounding of the gray matter of the medulla, even of
a small portion of it, near the origin of the pneumogastric
nerve, at once stops the action of the lungs and causes
death. In consequence of the importance of this part, it
has been termed the "vital knot." We find, also, that its
location within the skull is exceedingly well protected, it
being quite beyond the reach of any ordinary form of
harm from without.

50. The Functions of the Cranial Ganglia.— The
uses of the smaller gray masses lying at the basv. of the
brain are not well ascertained; and, on account of their
position, so remote from the surface, it would, at first, seem
well-nigh impossible to study them. But, from the results
following diseases in these parts, and from experiments
upon inferior animals, they are becoming gradually better
understood; and there is reason to believe that eventually
the physiological office of each part will be clearly ascer-
tained and defined. It is believed, however, but not abso-

49. The pneumogastric nerve? The feelings aroused by it? The "vital
knot?"

50. The uses of the smaller gray masses at the base of the brain ?

172 THE NERVOUS SYSTEM.

lutely proven, that the anterior masses, like the anterior
roots of the spinal nerves and the anterior columns of
the cord, are concerned in the production of motion; in
fact, that they are the central organs of that function.
The posterior gray masses are, on the contrary, supposed
to be the seat of sensation.

51. The Function of the Cerebellum. — The func-
tion of the cerebellum, or "little brain/' is the direction
of the movements of the voluntary muscles. When this
organ is the seat of disease or injury, it is usually observed
that the person is unable to execute orderly and regular
acts, but moves in a confused manner as if in a state of
intoxication. Like the larger brain, or cerebrum, it
appears to be devoid of feeling; but it takes no part in
the operations of the mind.

52. The Function of the Cerebrum. — The cere-
brum, or brain proper, is the seat of the mind; or, speak-
ing more exactly, it is the material instrument by which
the mind acts; and, as it occupies the highest position in
the body, so it fulfils the loftiest uses. All the other
organs are subordinate to it:* the senses are its messengers,
which bring it information from the outer world, and the
organs of motion are its servants, which execute its com-
mands. Here, as in the nervous apparatus of lower grade
already considered, the gray matter is the element of
power; and, in proportion as this substance increases in
extent, and in proportion to the number of convolutions
in the hemispheres, do the mental faculties expand.

53. There have been a few, but only a few, men of dis-
tinguished ability whose brains have been comparatively
small in size ; the rule being that great men possess large
brains. The relative weight of the brain of man, as com-

5 1 . Function of the cerebellum ? When it is diseased ?

52. Where is the seat of the mind? The subordination of the other organs?
The gray matter ?

53. What is stated of men in connection with the size of their brain ? With
the brains of other animals ?

THE NEKVOUS SYSTEM. 173

pared with the weight of the body, does not, in all instan-
ces, exceed that of the inferior animals; the canary and
other singing-birds have a greater relative amount of nerv-
ous matter than man ; bnt man surpasses all other crea-
tures in the size of the hemispheres of the cerebrum, and
.in the amount of gray substance which they contain.

54. It is a singular fact that this cerebral substance is
insensitive, and may be cut without causing pain. The
removal of a considerable quantity of the brain has taken
place, as the result of accident, without causing death, and
without even affecting seriously the intellect. A remark-
able case of injury of the brain is recorded, in which,
from the accidental explosion of gunpowder used in blast-
ing a rock, the " tamping-iron" was driven directly through
the skull of a man. This iron rod, three feet and seven
inches long, an inch and a quarter in diameter, and weigh-
ing more than thirteen pounds, entered the head below the
ear and passed out at the top of the skull, carrying with it
portions of the brain and fragments of bone. The man
sustained the loss of sight on one side, but otherwise
recovered his health and the use of his faculties. More-
over, disease has occurred, compromising a large portion
of the brain, without impairing the faculties of the mind,
when the disease was limited to one side only.

55. Impressions conveyed to the hemispheres from the
external world arouse the mental operations called
thought, emotion, and the will. These are the god-
like attributes which enable man to subjugate a world,
and afterward cause him to " sigh for other worlds to con-
quer;" which enable him to acquaint himself with the
properties of planets millions of miles distant from him,
and which give him that creative power by which he
Guilds and peoples the new worlds of poetry and art.

54. Sensitiveness of the brain substance? The removal of a portion of the
train ? State the remarkable case mentioned ?

55. Thought, emotion, and will ? What power do they give us ?

174 THE NERVOUS SYSTEM.

56. All these mental acts, and many others, are devel-
oped through the action of the brain ; not that the brain
and the mind are the same, or that the brain secretes
memory, imagination, or the ideas of truth and justice, as
the stomach secretes the gastric juice. But rather, as the
nerve of the eye, stimulated by the subtile waves of light,
occasions the notion of color, so the brain, called into
action by the mysterious influences of the immaterial soul,
gives rise to all the intellectual, emotional, and voluntary
activities of mankind.

57. The cerebrum, according to our present knowledge
of it, must be regarded as a single organ, which produces
different results, according as it is acted upon by the im-
material mind in different ways. Recent investigations,
however, seem to prove that the faculty of language is de-
pendent upon a small part of the left hemisphere of the
cerebrum, near the temple. At least, in almost every
instance where this part is diseased, the patient can no
longer express himself in speech and writing.

58. The Reflex Action of the Brain.— The reflex
function of the organs within the skull is very active and
important. Like that of the cord, it protects the body by
involuntary movements, it regulates the so-called vegeta-
tive acts, and it takes the place of the will in controlling
the voluntary muscles, when the attention is turned in
other directions. The reflex power of the medulla governs
the acts of respiration, which are absolutely and continu-
ously essential to life. Respiration is, as we have seen,
partly under the influence of the will; but this is due in
part to the fact that respiration is indirectly concerned in
one of the animal functions, that of speech.

59. Reflex action also occasions coughing and sneezing,

56. Are the brain and the mina identical?

57. What do we know of the cerebrum and its powers ?

58. The reflex function of the organs within the skull? The reflex power oi
the medulla ? Respiration ?

59. What else does reflex action occasion ? Winking? Other examples ?

THE NERVOUS SYSTEM. 175

whenever improper substances enter the air-passages.
Winking is an act of the same sort, and serves both to
shield the eyes from too great glare of light, and to pre-
serve them by keeping the cornea moist. Looking at the
am or other strong light, causes sneezing by reflex action.
Laughing, whether caused by tickling the feet or by some
happy thought, and also sobbing, are reflex acts, taking
place by means of the respiratory muscles.

60. Certain of the protective reflex movements call into
play a large number of muscles, as in the balancing of the
body when walking along a narrow ledge, or on a slippery
pavement. The dodging motion of the recruit, when the
first cannon ball passes over his head, is reflex -and invol-
untary. The fact that these involuntary, reflex acts are
performed with great precision, will explain why it is that
accidents seldom befall the somnambulist, or sleep-walker,
although he often ventures in most perilous places.

61. Walking, sitting, and other acts of daily life, be-
come automatic, or reflex, from habit : the mind is seldom
directed to them, but delegates their control to the medulla
and spinal cord. Thus a person in walking, may traverse
several miles while absorbed in thought, or in argument
with a companion, and yet be conscious of scarcely one in
a thousand of the acts that have been necessary to carry
his body from one point to another. By this admirable
and .beautiful provision, the mind is released from the
charge of the ordinary mechanical acts of life, and may
devote itself to the exercise of its nobler faculties. And it
is worthy of notice, that the greater the use of these facul-
ties, the more work does the reflex function assume and
perform ; and thus the employment of the one insures the
improvement of the other.

60. Muscles called into play by certain reflex movements ? The somnambulist *

61. What is said of walking and other acts in connection with the office per
formed by the medulla and spinal cord ?

176 REVIEW QUESTIONS.

QUESTIONS FOR TOPICAL REVIEW.

PAGE

1. State fully what is meant by the term vegetable function 148

2. To what is man indebted for his position as the head of the animal crea-

tion ? 148, 149

3. What can you state on the subject of special organs for separate functions ? 149

4. Describe, as fully as you can, the structure of the nervous system 149, 150

5. Describe the brain, its location, size, shape, and structure 150. 152

6. Describe the brain proper, or cerebrum 152, 153, 174

7. What connection is noticed between the cerebrum and mental

power ? 153, i72, 174

8. Describe the little brain, or cerebellum 153, 154, 173

9. Describe the spinal cord 154, 155, 155

10. What are the spinal nerves, and how are they arranged ? 156, 157

11. What is the character and substance of their tissues ? 157

12. State how the nerve-fibres perform their office, and give the illustra-

tion 157, 158

13. Describe the sympathetic system of nerves 158

14. State what is meant by the properties of nervous tissue, and give the

illustration 159, 160

15. Explain what is meant by the functions of the nerves, and give the

illustration 160, 101, 162

16. What is meant by a transient paralysis of a nerve ? Give the illustra-

tion 161, 162

17. What can you state of the rate of message-motion along a nerve ? 162

18. What are the functions of the spinal cord ? 162, 163, 104, 165

19. State what you can of the form of paralysis known as paraplegia 163

"20. What experiments, with results, upon the spinal cord are noted? 163, 164

21. Explain how injury of the cord may produce paralysis of motion in one

leg, and at the same time a loss of sensation in the other 164

22. Explain how, if the right hand be hurt, the left side of the brain is made to

feel the pain 105

23. Now, explain as fully as you can the direction of the fibres of the cord. 164, 165

24. What is understood by the reflex action of the cord ? 165

25. What experiments are mentioned to prove this power of the cord ? 165, 160

26. What are the uses of the reflex action of the cord ? 167-KO

27. What illustrations are mentioned to show such uses ? 167-170

28. What is the medulla oblongata ? 154, 170

29. What are the functions of the medulla oblongata ? 170, 171

30. What can you state of the functions of the cranial ganglia ? 171, 172

31. What are the functions of the cerebellum ? 172

32. What is the function of the cerebrum ? 172, 174

33. In what way does the size of the brain generally indicate- the character

of the man ? 172, 173

34. What facts show that the gray substance of the brain is insensitive * 173

35. Upon what does the faculty of language seem to depend ? 174

36. What has been observed in support of this statement ? 174

37. Of what importance is the reflex action of the brain ? 174, 175

3S. In what ways is this importance made manifest ? 174, 175

THE SPECIAL SENSES. 177

CHAPTER X.

THE SPECIAL SENSES.

The Production of Sensations — Variety of Sensations — General Sensi-
bility— Pain and its Function — Special Sensation, Touch, Taste,
Smell, Sight, and Hearing — The Hand, the Organ of Touch — TJie
Sense of Touch — Delicacy of Touch — Sensation of Temperature and
Weight— TJie Tongue the Organ of Taste— TJie Nerves of Taste—
The Sense of Taste and its Relations with tJie oilier Senses — TJie
Influence of Education on the Taste — The Nasal Cavities, or the
organs of Smell — TJie Olfactory Nerve — The Uses of the Sense of
Smell— The Sense of Sight — Light— The Optic Nerve— TJie
Eyeball and its Coverings — The Function of the Iris — The
Sclerotic, Choroid, and Retina — The Tears and their Func-
tion— The Movements of the Eyeball — The Function of Ac-
commodation— The Sense of Hearing and Sound — The Ear, or
the organ of Hearing — The External, Middle, and Internal Ear.

1. Production of Sensations. — We have already
seen that the true centre of sensation is some organ within
the skull, probably among the gray masses at the base of
the brain; but the mind never perceives impressions at
that point ; but, on the contrary, always refers them to the
external organs of sensation. Hence, it is convenient to
say, that those outer parts possess the property of sensibil-
ity. For instance, we say that we hear with the ear, taste
with the tongue, and feel with the fingers. That this is
not the exact truth is proven by the fact, that whenever
the nerve connecting one of these organs with the brain is
severed, it at once loses its capacity for sensation.

2. Consciousness, another facujty of the brain, is neces-
sary to complete a sensation. During sleep, and in other
unconscious states, the usual impressions are presented to

1 . True centre of sensation ? Place of the mind's impressions ? What is it
convenient to say ? What further is stated ?

2. Consciousness ? During sleep? In profound insensibility ?

S*

THE SPECIAL SENSES.

the ear, the nose, and the skin, but they fail to excite sen-
sations, because the nerve-centres are inactive. In pro-
found insensibility, from chloroform or ether, a limb may
be removed without occasioning the least feeling.

3. Variety of Sensations. — All animals have some
degree of sensibility. It is of course feeble and indistinct
in the lower forms of life, but increases in power and vari-
ety as we ascend the scale. In the earth-worm, the nerv-
ous system is very simple, the sensibility being moderate
and alike in all parts : hence, if its body be cut into two
pieces, each piece will have the same degree of feeling as
before. As we approach man, however, the sensations
multiply and become more acute; the organs are more
complex, and special parts are endowed with special gifts.
These special organs cannot be separated from the rest of
the body without the loss of the functions they are de-
signed to exercise.

4. The lowest form of sensation, that of simple contact,
is possessed by the lowest of the animal creation. The
highest forms are those by which we are enabled to know
the properties of external objects, such as shape, size,
sound, and color. A variety of means of communicating
with the outer world is the necessary possession of a high
intelligence. Sensations are modified by use. They be-
some more acute and powerful by moderate exercise ; or,
they are dulled by undue excitement. The former is
shown by the acute hearing of the Indian, by the sharp
sight of the sailor, and by the delicate touch of the blind.
The latter is exemplified by the impaired hearing of the
boiler-maker, and the depraved taste of him who uses
pungent condiments with his food. Again, impressions
habitually presented may not be consciously felt; as is
the case with the rumbling of carriages in a neighboring

3. Sensibility in animals ? In the earth-worm ? In man ?

4. The lowest form of sensation? The highest? Sensations, how modified?
What further can you state as to habitual impressions?

THE SPECIAL SENSES. 170

street, or the regular ticking of a clock. All sensations
become less vivid with the advance of age, especially hear-
ing and vision.

5. General Sensibility. — There is a property pos-
sessed by nearly all parts of the human body which we
call general sensibility. We have recently seen that the
brain is wholly insensitive, and may be cut or pinched
without pain. The same is true of the nails, hair, the
Scarf-skin or external covering of the body, and a few other
structures. In these parts no nerves are found. On the
other hand, the sensibility of the true skin, and of mucous
membranes, as of the eye and nose, is exquisite, these or-
gans having a large supply of sensory nerve-fibres. The
bones and tendons have less of these fibres, and are only
moderately sensitive.

6. The sensibility of any part of the body, then, de-
pends upon the number of nerves present; and, as a rule,
the nervous supply is proportional to the importance of
the part, and to its liability to injury. When, therefore, a
surgical operation is performed, the most painful part of it
is the incision through the skin ; the muscles, cartilage,
and bone being comparatively without sensation. Hence,
if we could benumb the surface, certain of the lesser oper-
ations might be undergone without great inconvenience.
This is, in fact, very successfully accomplished by means of
the cold produced by throwing a spray of ether, or of some
other rapidly evaporating liquid, upon the part to be cut.

7. Tickling is a modification of general sensibility. At
first, it excites a pleasurable sensation, but this soon passes
into pain. It. is only present in those parts where the
sense of touch is feeble. But all impressions are not
received from without: there are, also, certain internal

5 . General sensibility ? What have we seen as regards the brain ? Of what
other structures is the same true ?

6. The cause of sensibility ? Painful part in a surgical operation ? Benumb-
ing the surface ? How done by ether ?

7. Tickling ? Internal sensations ? The nerves of general sensibility ?

180 THE SPECIAL SENSES.

sensations, as they are called, which depend upon the con-
dition of the internal organs, such as appetite, hunger,
thirst, the sense of satisfaction after taking food, dizziness
when looking down from some lofty position, lassitude,
drowsiness, fatigue, and other feelings of comfort or dis-
comfort. General sensibility, whether of the internal or
external organs of the body, chiefly depends upon the
sensory fibres of the spinal nerve. The face, however, is
supplied by the sensory cranial nerves. The sympathetic
system has a low grade of feeling in health ; but disease in
the parts served by it arouses an intense degree of pain.

8. The Sensation of Pain.— What then is pain 9 Is
it identical with ordinary sensibility ? There seems to be
some necessary connection between the two feelings, for
they take place through the same channels, and they are
alike intense in the same situations. But sensibility
habitually contributes to our sources of pleasure, the very
opposite of pain ; hence, these feelings cannot be identical.

9. Pain must, therefore, be a modification of the general
sensibility, which follows an excessive degree of excitement
of the nerves ; there being a natural limit to the amount of
stimulation which they will sustain. So long as this limit
is observed, the part excited may be said to be simply sen-
sitive; but when it is exceeded, the impression becomes
painful. This difference between sensibility and pain is
well shown by the effects of sunlight upon the eye. The
indirect illumination of the sun arouses only the former
feeling, and is indispensable to our comfort and existence ;
while the direct ray received into the eye occasions great
pain.

10. The Uses of Pain. — The dread of pain is a valu-
able monitor to the body. It puts us on our guard in the
presence of danger; teaches moderation in the use of our

8. Connection between pain and sensibility?

9. Explain the difference between pain and sensibility.

1O. Dread of pain * How may its value be appreciated ? Example.

THE SPECIAL SENSES. 181

powers ; indicates the approach of disease ; and calls at-
tention to it when present. The word disease, in fact,
according to its original use, had reference simply to the
pain, or want of ease, which commonly attends disordered
health. When we observe the serious mishaps which occur
when sensibility and pain are absent, we cannot fail to
appreciate its value. For example, a paralytic in taking a
foot-bath, forgets to test its temperature, and putting his
limbs into water while it is too hot, is severely scalded
without knowing it.

11. A traveller, overcome by cold and fatigue, lies down
and falls asleep near a large fire, and when he is aroused in
the morning, it is discovered that one of his feet has been
insensibly destroyed. A grain of sand, lodging in an insen-
sitive eye, may cause inflammation and even the loss of
sight. If intense light were not painful to the eye, many
a child would innocently gaze upon the glories of the sun
to the ruin of his sight.

12. Pain is, indeed, a present evil, but its relations with
the future prove its mission merciful. Painful impressions
cannot be recollected from past experience ; and they can-
not be called into existence by the fancy. Considered in
the light of results, pain has a use above that of pleasure ;
for while the immoderate pursuit of the latter leads to
harm, the tendency of pain is to restrict the hurtful courses
of life, and in this manner to protect the body.

13. The relations of pain to pleasure are thus described
by the eminent physiologist, Magendie: — "By these sensa-
tions Nature induces us to concur in the order which she
has established among organized beings. Though it may
appear like sophistry to say that pain is the shadow of
pleasure, yet it is certain that those who' have exhausted
the ordinary sources of pleasure have recourse to the

1 1 . The case of the traveller ? Grain of sand ? The <?nn and child ?

1 2. Mission of pain ? Painful impressions compared with those of pleasure ?

13. What does Magendie say of the relation of pain to pleasure ?

182 THE SPECIAL SENSES.

causes of pain, and gratify themselves by their effects. Do
we not see in all large cities, that men who are debauched
and depraved find agreeable sensations, where others ex-
perience only intolerable pain ?"

14. As to painful sensation among the inferior animals,
the plan of Nature seems to be, that the higher the intel-
ligence of the creature, and the more complete its power
of defence, the more acute is its sensibility. We infer,
therefore, that animals low in the scale of existence, and
helpless, are not very liable to suffer pain.

15. Special Sensation. — The sensations of simple
contact and pain are felt by nearly all parts of the system,
whether external or internal, and are the necessary con-
sequence of the general sensibility ; but, so far as the ob-
jects which surround us are concerned, these impressions
are vague and passive in character, and inform the mind
of none of the properties or powers of these objects. Be-
sides these feelings, therefore, man is endowed with certain
special sensations, which are positive and distinct in char-
acter, and which he can call into exercise at will, and em-
ploy in the pursuit of knowledge. For reasons relating to
the original constitution of the body, these sensations are
to be regarded as modifications of the general sensibility
already alluded to, constructed with special reference to
the different forces of Nature, of which we have any
knowledge, such as heat, motion, gravity, sunlight, and
the like.

16. These distinct and active faculties are termed the
special senses, and are five in number, viz., Touch, Taste,
Smell, Sight, and Hearing. For the exercise of these
senses, special organs are furnished, such as the hand, the
tongue, the nose, the eye, and the ear. The manner in
which the nerves of special sense terminate, varies in the

14. The law of Nature as regards painful sensations among animals ?

15. The sensation of contact and pain? Special sensations of man? How
regarded ?

1 6. What are the special senses ? Special organs for them ?

THE SPECIAL SENSES. 183

case of each organ, so that each is adapted to one set of
sensations alone, and is incapable of perceiving any other.
Thus the nerve of hearing is excited by the undulations of
sound, and not by those of light, while the reverse is true
of the nerve of sight; and the nerve of smell can appreciate
neither of them, being capable only of taking cognizance
of the odorous properties of bodies.

17. By some writers six senses are accorded to man ; the
additional one being either the sense of temperature, for as
we shall presently see this is not the same as touch; or
according to others, the muscular sense by which we are
enabled to estimate the weights of bodies. The latter also
differs in some respects from the sense of touch.

18. Organs of Touch. — The sense of touch is pos-
sessed by nearly all portions of the general. surface of the
body, but it finds its highest development in the hands.
The human hand is properly regarded as the model organ
of touch. The minute structure of the skin fits it admi-
rably for this form of sensation : the cuticle, or scarf-skin,
is fine and flexible, while the outis, or true skin, contains
multitudes of nerve-filaments, arranged in rows of papillm,
or cone-like projections, about one-hundredth of an inch in
length. It is estimated that there are 20,000 of these papillae
in a square inch of the palmar surface of the hand. Now,
although the nerves of the cutis are the instruments by
which impressions are received and transmitted to the
brain, yet the cuticle is essential to the sensation of touch.
This is shown by the fact that whenever the true skin is
laid bare, as by a burn or blister, the only feeling that it
experiences from contact is one of pain, not that of
touch.

19. The office of the cuticle is thus made evident : it is
to shield the nerve filaments from direct contact with ex-

1 7. What, is said in relation to one more than the five senses ?

18. The sense of touch, how prevalent ? What is said of the hand ?

19. Office of the cuticle ? Tips of the fingers ? The fingers with thumb ?

184 THE SPECIAL SENSES.

fcernal objects. At the tips of the fingers, where touch is
most delicate, the skin rests upon a cushion of elastic
material, and receives firmness and permanence of shape
by means of the nail placed upon the less sensitive side.
Besides these favorable conditions, the form of the arm is
such, and its motions are so easy and varied, that we are
able to apply the test of touch in a great number of direc-
tions. The slender, tapering fingers, with their pliant
joints, together with the strong opposable thumb, enable
the hand to mold itself upon and grasp a great variety of
objects ; so that great as are the delicacy and grace of the
hand, it is not wanting in the elements of power.

20. Its beauty and adaptation to the wants of man have
made the hand an attractive theme for philosophers.
They do not, however, always agree in their conclusions.
One has- the opinion that man has acquired his intelligence
and achieved his place as " lord of creation," because he
has this organ. Buffon, in effect, declares that with fingers
twice as numerous and twice as long, we would become
proportionally wiser; but Galen long ago took a more
reasonable view, when he taught that " man is the wisest
of animals, not because he possesses the hand ; but because
he is the wisest and understands its use, the hand has been
given to him; for his mind, not his hand has taught him
the arts." Another has well said, that " no one can study
carefully the human hand and fail to be convinced of the
existence of the Deity."

21. The Sense of Touch. — Touch is the simplest of
the senses. It is that which the child first calls into ex-
ercise in solving the early problems of existence ; and it is
that which is in the most constant use throughout life.
We are brought by the touch into the most intimate rela-
tions with external objects, and by it we learn the greater
number, if not the most important, of the properties of

20. What special importance is attributed to the hand?

2 1 . The simplicity of touch ? What does it teach us ?

THE SPECIAL SENSES. 185

these objects; such as size, figure, solidity, motion, and
smoothness or roughness of surface.

22. The sense of touch assists the other senses, especially
that of sight, giving foundation and reality to their per-
ceptions. Without it, the impressions received by the eye
would be as vague and unreal as the figures that float
through our dreams. A boy who had been blind from
birth, at the age of twelve years received sight by means
of a surgical operation : at first, he was unable to distinguish
between a globe and a circular card, of the same color, be-
fore he had touched them. After that, he at once recog-
nized the difference in their form. He knew the peculiari-
ties of a dog and a cat by feeling, but not by sight, until
one day, happening to take up the cat, he recognized the
connection of, the two sorts of impressions, those of touch
and sight ; and then, putting the cat down, he said : " So,
puss, I shall know you next time."

23. Touch is considered the least liable to error of all
the senses ; yet, if that part of the skin by which the sense
is exercised is removed from its customary position, a false

Fro. 45.

impression may be created in the mind. This is well il-
lustrated by an experiment, which dates from the time of
Aristotle. If we cross the middle finger behind the fore-

22. Importance of the sense of touch to the development of the other senses?

23. Liability of touch to err? Describe the illustration.

186 THE SPECIAL SENSES.

finger, and then roll a marble, or some small object, upon
the tips of the fingers (see Fig. 45), the impression will be
that two marbles are felt. If the fingers, thus transposed,
be applied to the end of the tongue, two tongues will be
felt. When the nose is accidentally destroyed, the surgeon
sometimes performs an operation for the purpose of form-
ing a new one, by transplanting a partially removed piece
of the skin of the forehead upon the injured part : then, if
the new nose be touched or pinched, the feeling is referred
to the forehead. This fact illustrates one important truth,
that the nerves will re-unite after they have been cut, and
feeling will be restored : if it were otherwise, a succession
of slight cuts upon the fingers would seriously impair their
tactile sensibility.

24. The Delicacy of Touch. — Although the hand
is the proper organ of this sense, yet it is exercised by
various parts of the body, their degree of sensibility being
proportional to the number of papillae they contain. The
varying degrees of tactile delicacy of the different parts of
the surface have been measured, in an ingenious manner,
by means of a pair of compasses, tipped with small pieces
of cork. The two points of the compasses are touched at
the same moment to the skin, the eyes being closed, and it
is found that, in sensitive parts, the distance between the
points maybe quite slight, and yet each be plainly felt;
while, in less sensitive parts, the points of the compasses
are felt as a single point, although they are separated one
or two inches.

25. At the tips of the fingers, the distance between the
points being one-twentieth of an inch, a double impression
is felt. The distance must be twice as great, for the palm ;
four times as great, for the lips ; and, on the forehead, it
must be twenty times greater. At the middle of the back,
where the touch is least acute, the points must be sepa-

24. The delicacy of tonch ? Experiments with a pair of compasses ?

25. Further experiments and results ?

THE SPECIAL SENSES. 187

rated more than two inches before they can be separately
felt. Therefore, the sense of touch in the fingers is said to
be fifty times more delicate than upon the posterior sur-
face of the body.

26. Exquisite delicacy of touch is attained by practice.
This is shown in many of the lighter and more graceful
employments of daily life. Without it, the skill of the
painter, sculptor, and musician would be rude indeed. By
training, also, the physician acquires the tactus eruditus,
or discriminating touch ; but among the blind, delicacy of
touch is most remarkable, and it here finds its highest
value; for its possession, in a measure, compensates the
loss of sight by enabling them to read, by means of raised
letters, to work with certain tools, and even to play upon
musical instruments. A person born without sight, and
without hearing or voice, may, by the education of the
touch, be rescued from apparent imbecility, and be taught
not only to read and write, but even to perform household
and other useful labors.

27. Sensations of Temperature and Weight.—
Each of these sensations has been described by the physi-
ologists as a special sense, and they are rival candidates, so
to speak, for the position and title of the sixth sense. In the
sensation of temperature, or the thermal sense, touch bears
a part, but the two feelings appear to be distinct. In proof
of this, we observe, firstly, that they are not alike intense
in the same situations ; as, for example,, the skin of the face
and elbow, where the sense of touch is feeble, is very sensi-
tive to impressions of heat and cold. Secondly, the ability
to recognize temperature may be lost by paralysis, while
the sensibility of touch remains unaffected. When the
skin comes in contact with a very hot substance, the sen-
sation felt is that of pain, not of touch. In like manner, a

26. Exquisite delicacy of touch ? The same among the blind ?

27. Rival candidates for the sixth sense? Give the two reasons on the sub-
ject.

188 THE SPECIAL SENSES.

very cold substance causes pain, not the feeling of cold.
So that a red-hot iron, and solid carbonic acid (the tem-
perature of which is 108° below zero), feel alike ; and each,
if pressed slightly, will produce a blister.

28. The muscular sense, by some considered distinct
from touch, gives rise to the sensations of weight, and
other forms of external resistance. That this feeling
exists, is shown by the following simple experiment. If
the hand be placed flat upon a table, and a somewhat
heavy weight be put into it, touch alone is exercised
and a feeling of pressure results; but if the hand be
raised, a certain amount of muscular effort must be put
forth, and thus the sensation of weight is recognized.
Through the muscular sense, precision of effort is rendered
possible ; for by it we learn to adjust the force exerted to
the weight of the object to be lifted, moved, or carried.
Without it, all our movements would necessarily become
ill-regulated and spasmodic. In cases of disease, where the
sensibility of the lower limbs is lost, while power of motion
remains, the patient is able to stand erect so long as he
can see his limbs; but just as soon as his eyes are closed,
he begins to waver, and will fall unless supported.

29. The Organ of Taste.— The tongue is the special
organ of the sense of taste ; but the back part of the mouth
also possesses this faculty. The tongue is a muscular
organ, the muscles composing it being so numerous and
interwoven as to give it the freedom and variety of motion
which it possesses. It can curve itself upward or down-
ward; it can extend or contract itself; and, with its point,
can sweep the cavity of the mouth, in all directions, in
the search for scattered particles of food.

30. The upper surface of the tongue is peculiar, being
marked by the presence of innumerable paptffo, some of

28. The muscular sense ? State what is paid to illustrate the subject.

29. The or<ran of taste ? The tonprne ? Its powers of motion ?
ftO. Peculiarities of the tongue ? Uses of the papillae ?

THE SPECIAL SENSES. 189

which are of microscopic size, resembling those that
abound in the fingers, and in other parts of the body
that have the sense of touch. Others are much larger,
and give to the tongue its roughness of feeling and ap-
pearance. Through the medium of these papillae, the
tongue receives impressions of touch and temperature, as
well as taste : indeed, its extremity is fully as delicate, in
respect to tactile sensations, as the tips of the fingers them-
selves. It can recognize the two points of the compasses
when separated not more than one-twenty-fourth of an
inch; the back of it is much less sensitive to touch, while
at the same time it is more highly sensitive to impressions
of taste.

31. Each lateral half of the tongue resembles the other
in structure, and each receives the same number of nerves
— three. One of these regulates motion, the other two are
nerves of special sense. One of the latter supplies the
front half of the tongue, and is called the gustatory nerve.
This is a branch of the great cranial nerve, called the
"fifth pair," which ramifies in all parts of the face. The
back of the tongue is endowed with the power of taste
through a nerve known as the glosso-pliaryngeal, because
it is distributed both to the tongue and throat. This dif-
ference in the nervous" supply of the tongue becomes signif-
icant, when we learn, as we shall presently, that each part
of it perceives a different class of flavors.

32. The Sense of Taste. — Taste is the special sense
by means of which we discover the savors, or flavoring
properties of the substances, which* come in contact with
the tongue. Mere contact with the surface of the tongue,
however, is not sufficient, but contact with the extremities
of the nerves of taste within the papillae is required. In
order that the substance to be tasted may penetrate the

3 1 . Resemblance fn the parts of the tongue ? Powers and functions of thf
parts ?

32. Taste ? What are the requisites to taste ?

190 THE SPECIAL SENSES.

cells covering the nerves, it must either be liquid in form,
or readily soluble in the watery secretion of the mouth,
the saliva. The tongue must be moist also. If the sub-
stance be insoluble, as glass or sand, or the tongue dry, the
sense of taste is not awakened. In sickness, when the
tongue is heavily coated, the taste is very defective, or, as
is frequently expressed, "nothing tastes aright."

33. All portions of the tongue are not alike endowed
with the sense of taste, that function being limited to the
posterior third, and to the margin and tip of this organ.
The soft palate, also, possesses the sense of taste ; hence,
an article that has an agreeable flavor may very properly
be spoken of as palatable, as is often done. All parts of
the tongue do not perceive equally well the same flavors.
Thus, the front extremity and margin, which is the por-
tion supplied by the "fifth pair" of nerves, perceives more
acutely sweet and sour tastes; but the base of the tongue,
supplied by the glosso-pharyngeal nerve, is especially sen-
sitive to salt and bitter substances. The nerve of the front
part of the tongue, as before stated, is in active sympathy
with those of the face, while the relations of the other
nerve are chiefly with the throat and stomach ; so that
when an intensely sour taste is perceived, the countenance
is involuntarily distorted, and is said to wear an acid ex-
pression. On the other hand, a very bitter taste affects
certain internal organs, and occasions a sensation of nau-
sea, or sickness of the stomach.

34. Relations of Taste with other Senses.—
Taste is not a simple sense. Certain other sensations, as
those of touch, temperature, smell, and pain, are blended

-and confused with it; and certain so-called tastes are really
sensations of another kind. Thus an astringent taste, like
that of alum, is more properly an astringent feeling, and

33. Portions of the tongue endowed with taste? - Where else does the sense
!od»e ? What is stated in respect to sweet and bitter flavors ? Reflex effects men-
tioned ?

34. What is stated of the relations of taste with other senses ?

THE SPECIAL SENSES. 191

results from an impression made upon the nerves of touch,
that ramify in the tongue. In like manner, the qualities
known as smooth, oily, watery, and mealy tastes, are depend-
ent upon these same nerves of touch. A burning or pungent
taste is a sensation of pain, having its seat in the tongue and
throat. A cooling taste, like that of mint, pertains to that
modification of touch called the sense of temperature.

35. Taste is largely dependent upon the sense of smell.
A considerable number of substances, like vanilla, coffee,
and garlic, which appear to possess a strong and distinct
flavor, have in reality a powerful odor, but only a feeble
taste. When the sense of smell is interfered with by hold-
ing the nose, it becomes difficult to distinguish between sub-
stances of this class. The same effect is frequently observed
when smell is blunted during an ordinary cold in the head.
Sight also contributes to taste. With the eyes closed, food
appears comparatively insipid; and a person smoking
tobacco in the dark is unable to determine by the taste
whether his cigar is lighted or not. Accordingly, it is not
a bad plan to close the nose and shut the eyes when about
to swallow some disagreeable medicine.

36. Influence of Education on the Taste.— The
chief use of the sense of taste appears to be to act as a
guide in the selection of proper food. Hence its organs are
properly placed at the entrance of the digestive canal. As
a general rule, those articles which gratify the taste are
wholesome ; while the opposite is true of those which im-
press it disagreeably. This statement is more exact in
reference to the early years of life than to later years,
when, by reason of mischievous habits, the sense of taste
has become dulled or perverted. The desires of a child
are simple ; he is fully satisfied with plain and wholesome
articles of diet, and must usually "learn to like" those

35. Its dependence on smell? on

36. The chief use of the sense of taste? The position of its organs ? The rule
as regards wholesome and unwholesome food ? Remarks- respecting the rule ?

192 THE SPECIAL SENSES.

which have a strongly marked flavor. Accordingly, it is
far easier at this age to encourage the preference for plain
food, and thus establish healthful habits, than later in life
to uproot habits of indulgence in stimulating substances,
after their ill effects begin to manifest themselves.

37. The tastes of men present the most singular diversi-
ties, partly the result of necessity and partly of habit or
education. The Esquimaux like the rank smell of whale
oil, which is a kind of food admirably suited to the require-
ments of their icy climate ; and travellers who go from our
climate to theirs are not slow to develop a liking for the
same articles that the natives themselves enjoy. The sense
of taste is rendered very acute by education, as is shown in
an especial manner by those who become professional
" tasters" of tea and wine.

38. The Sense of Smell— the Nasal Cavities.
—The sense of smell is located in the delicate mucous

membrane which lines the interior of the nose. That
prominent feature of the face, the nose, which is merely
the front boundary of the true nasal organ, is composed
partly of bone and partly of cartilage. The upper part of
it is united with the skull by means of a few small bones ;
to which circumstance is due its permanence of shape.
The lower portion, or tip of the nose, contains several thin
pieces of cartilage, which render it flexible and better able
to resist the effects of blows and pressure. Behind the
nose we find quite a spacious chamber, separated from
the mouth by the hard palate, forming the "roof of the
mouth," and by the soft palate (see Fig. 46) ; and divided
into two cavities by a central partition running from be-
fore backward.

39. These nasal cavities, constituting the true beginning
of the air-passages, extend from the nose backward to the

37. Diversity in tastes of men ? How shown ? The education of the sense of
taste ?

38. Location of the sense of smell? The nose? " Roof of the month?"

3 J). Cavities of the nose ? Obstruction of the passage of air through them ?

THE SPECIAL SENSES.

193

upper opening of the throat, and rise as high as the junc-
tion of the nose with the forehead. The inner wall of
each cavity is straight and smooth ; but from the outer
wall there jut into each cavity three small scroll-like
bones. The structure of these bones is very light, and
hence they have been called the " spongy" bones of the nose.
In this manner, while the extent of surface is greatly in-
creased by the formation of these winding passages, the
cavities are rendered extremely narrow; so much so, in fact,
that a moderate swelling of the mucous membrane which
lines them, as from a cold, is sufficient to obstruct the pass-
age of air through theni.

40. The Nerve of Smell. — The internal surface of
the nasal passages is covered by a delicate and sensitive
mucous membrane. Its surface is quite extensive, follow-
ing as it does, all the inequalities produced by the curved
spongy bones of the nose. The upper portion of it alone
is the seat of smell, since that part alone receives branches
from the "first pair"
of cranial nerves, or
the olfactory nerve,
which is the special
nerve of smell (see
Fig. 43). In Fig. 40
is shown the distri-
bution of this nerve,
in the form of an
intricate network
upon the two upper

Spongy bones. The FlG' 46--SECTION OF THE RIGHT NASAL CAVITY.

nerve itself (1) does not issue from the skull, but rests
upon a thin bone which separates it from the cavity of the
nose; and the branches which proceed from it pass through
this bone by means of numerous small openings. The en-

4O. The special nerve of smell ? Its location ?

9

THE SPECIAL SENSES.

graving represents the outer surface of the right nasal
cavity; the three wave-like inequalities, upon which the
nervous network is spread out, are due to the spongy bones.
The left cavity is supplied in the same manner.

41. The nerves which ramify over the lower part of the
membrane, and which endow it with sensibility to touch
and pain, are branches of the " fifth pair" of nerves. An
irritation applied to the parts where this nerve is distrib-
uted occasions sneezing, that is, a spasmodic contraction
of the diaphragm; the object of which is the expulsion of
the irritating cause. The manner in which the olfactory
nerve-fibres terminate is peculiar. Unlike the extremities
of other nerves, which are covered in by a greater or less
thickness of tissue, these come directly to the surface of
the mucous membrane, and thus come into very close con-
tact with the odorous particles that are carried along by the
respired air. The surface is at all times kept in a moist
condition by an abundant flow of nasal mucus ; otherwise
it would become dry, hard, and insensitive from the con-
tinual passage of air to and fro in breathing. Birds,
which respire more actively than men, have a special
gland, for secreting a lubricating fluid, located in the air-
passages of the head.

42. The Uses of the Sense of Smell, — Smell is
the special sense which enables us to appreciate odors.
Touch, as we have seen, is largely concerned with solid
bodies; and taste, with fluids, or with solids in solution.
Smell, on the other hand, is designed to afford us informa-
tion in reference to substances in a volatile or gaseous
form. Invisible and subtile particles emanate from odor-
ous bodies, and are brought by the respired air in contact
with the terminal filaments of the olfactory nerve, upon
which an agreeable or disagreeable impression is produced.

4 1 . Branches of the " fifth pair" of nerves ? Nasal mucus ? Birds ?
42. Smell? Touch? Taste? Design of smell ? Invisible and gaseous part*
cles ? The extreme fineness of the particles ? Musk ? In other cases ?

THE SPECIAL SENSES. 195

The fineness of the particles that constitute odors is often so
extreme, that they elude all attempts to measure or weigh
them. A piece of musk, for instance, may be kept for sev-
eral years, constantly emitting perfume, without any ap-
preciable loss of weight. In other cases, a loss of substance
is perceptible, such as the essential oils, which enter into
the composition of the ordinary perfumes.

43. Smell, like taste, aids us in the choice of proper
food, leading us to reject such articles as have a rank or
putrid odor, and which are, as a rule, unfit to be eaten.
The highest usefulness of this sense, however, consists in
the protection it affords to the organs of respiration. Sta-
tioned at the gateways of the air-passages, it examines the
current of air as it enters, and warns us of the presence of
noxious gases, and of other and generally invisible ene-
mies to health. Not all dangerous vapors are offensive,
but almost all offensive vapors are unfit to be breathed. A
number of small stiff hairs grow from the margin of
the nostrils to prevent the entrance of dust and other at-
mospheric impurities, which would be alike injurious to the
olfactory mucous membrane and to the lungs. The benev-
olent design of the Maker of our bodies may be observed in
all parts of their mechanism ; but, probably, in none is it
more clearly displayed than in connection with the sense
of smell.

44. The sense of smell is developed in a remarkable de-
gree in certain of the inferior animals, and is especially
acute in reference to the peculiar emanations that appear
to characterize the different animals. The lion and other
carnivorous beasts scent their prey from a great distance;
and the fox-hound is able to track the fox through thickets
and over open country for many miles; while the timid,
helpless herbivora, such as the deer and sheep, find in the

43. Aid given by ymell? The highest use of the sense? Explain the manner.

44. Sense of smell in the inferior animals? How, and in what cases, illus-
trated ?

196 THE SPECIAL SENSES.

sense of smell a means of protection against their natural
enemies, of whose approach they are in this manner warned.
By training this sense in the dog, and making it subservi-
ent to his use, man is able to hunt with success certain shy
and very fleet animals, which otherwise he could but sel-
dom approach. Among men, individuals differ greatly in
respect to the development of this sense ; and especially
in certain savage tribes it is found to be extremely deli-
cate. Humboldt states that the natives of Peru can, by
this sense, distinguish in the dark between persons of dif-
ferent races.

45. The Sense of Sight. — Sight, or Vision, is the
special sense by means of which we appreciate the color,
form, size, distance, and other physical properties of the
objects of external nature. Primarily, this sense furnishes
us with information concerning the different shades of
color and the different degrees of tightness: these are
the simple sensations of sight, such as the yellowness and
glitter of a gold coin. In addition to these, there are com-
posite visual sensations, produced by the joint action of
the other senses and by the use of the memory and judg-
ment; such as, m the case of the coin, its roundness,
solidity, size, its distance and direction from us. So that-
many of our sensations, commonly considered as due to
sight, are in reality the results of intellectual processes
which take place instantaneously and unconsciously.

• 46. This faculty not only has value in the practical
every-day affairs of life, but it contributes so largely to the
culture of the intellect and to our higher forms of pleasure,
that some writers are disposed to rate it as the first and
most valuable of the senses. Others, however, maintain
that the sense of hearing does not yield in importance to
that of sight; and they cite in support of their position

45. What is sight? What information docs it furnish ? Composite visual sen-
cat ions ?

46. Comparison between sight and hearing? Relative capacity of deaf and
blind?

THE SPECIAL SENSES. 19?

the fact that the blind are commonly cheerful and gay,
while the deaf are inclined to be morose and melancholy.
In respect to the relative capacity for receiving education
in the deaf and blind, it is found that the former learn
more quickly, but their attainments are not profound ;
while the blind acquire more slowly, but are able to study
more thoroughly.

47. Light. — The Optic Nerve. — Unlike the senses
previously considered — touch, taste, and smell — sight does
not bring us into immediate contact with the bodies that
are examined; but, by it, we perceive the existence and
qualities of objects that are at a greater or less distance
from us. In the case of the stars, the distance is incalcu-
lable, while the book we read is removed but a few inches.
Light is the agent which gives to this sense its wide range.
The nature of this mysterious force is not known, and it is
not here to be discussed; since its study belongs more
properly to the province of natural philosophy.

48. It is sufficient, in this connection, to state that the
theory of light now generally accepted, and which best
explains the facts of optics, is that known as the undula-
tory theory. This theory supposes that there exists an
intangible, elastic medium, which fills all space, and pene-
trates all transparent substances, and which is thrown into
exceedingly rapid undulations or waves, by the sun and
every other luminous body; the undulations being propa-
gated with extreme rapidity, and moving not less than
186,000 miles in a second.

49. These waves are thought to produce in the eye the
sensation of light, in the same manner as the sonorous
vibrations of the air produce in the ear the sensation of
sound. That part of the eye which is sensitive to these
waves is the expansion of the optic nerve. It is sensitive

47. Sight, unlike the other senses ? In the case of the stars ?

48. The undulatory theory oflight? What does the theory suppose ?

49. The sensation of light V Optic nerve ?

198 THE SPECIAL SENSES.

to no other impression than that of light, and it is the only
nerve which is acted upon by this agent. The optic nerve,
also called the " second pair" of cranial nerves, is the means
of communication between the eye and the brain.

50. The two nerves constituting the pair, arise from
ganglia lying at the base of the cerebrum, one of them on
each side; from which points they advance to the eyes,
being united together in the middle of their course in the
form of the letter X (Fig. 43 — 2). By this union the two
eyes are enabled to act harmoniously, and in some respects
to serve as a double organ. And by reason of this same in-
timate nervous communication, when serious disease affects
one eye, the fellow-eye is extremely liable to become the
seat of sympathetic inflammation; and this, if neglected,
almost certainly results in hopeless blindness.

51. The Organ of Sight.— The Eye.— The proximity
of the eye to the brain, and the important part it per-
forrfis in giving expression to the emotions, have given it
the name of "the window of the soul." The exceeding
beauty of its external parts, and the high value of its func-
tion, have long made this organ the subject of enthusiastic
study. It is chiefly within the last twenty years, however,
that this study has been successful and fruitful of practical
results. Several ingenious instruments have been invented
for the examination of the eye in health and disease, and
new operations have been devised for the relief of blindness
and of impaired vision. As a result, it is now a well-
marked fact that, in civilized lands, the number of those
who suffer from loss of sight is proportionally much less
than in countries where science is less known and culti-
vated.

52. The most obvious fact in respect to the apparatus of

5O» The two nerves constituting the pair of nerves ?

51. Why is the eye called the '• window of the soul?11 Why, the subject of
enthusiastic study ?

52. The most obvious fact? The consequence? The next thing noticed?
Its range of view ? Of what does the organ of vision consist ?

THE SPECIAL SENSES. 199

sight is that there are two eyes, which may either act to-
gether as one, and be fixed upon one object, or one eye may
be used independently of the other. In consequence of
this arrangement the loss of one eye does not necessitate
blindness, and, in fact, it not infrequently happens that the
sight of one eye may be long impaired or lost before the
fact is discovered. We next notice that it is placed at the
most elevated part of the body, in front, and near the brain.
It also commands a wide range of view, being itself moved
with great rapidity, and being further aided by the free
motion of the head and neck. The organ of vision consists
essentially of two parts : the optical instrument itself — the
eyeball — and its enveloping parts, or the case in which the
instrument is kept free from harm. The latter, which are
external, and which we shall first consider, are chiefly the
Orbits, the Eyelids, and the apparatus for the Tears.

53. The Orbits. — The eyeball, which is a delicate
organ, is well defended against external injury within the
orbits or bony sockets of the head. These are deep conical
hollows, bounded in part by the bones of the skull, and in
part by those of the nose and cheek. The orbit juts out
beyond the most exposed portion of the eyeball, as may be
seen by laying a book over the eye, when it will be found
that no part of the eyeball, unless it be very prominent,
will be touched by the book ; so that the only direction in
which an injury is liable to be received is immediately in
front of the eye. The overhanging brow is itself covered
by a layer of thick skin, studded with short, stout hairs,
which are so bent as to prevent the perspiration from run-
ning into the eye and obscuring vision. Through a hole
in the bottom of the orbit, the nerve of sight passes out-
ward from the brain. The orbit also contains a considera-
ale amount of a fatty tissue, upon which, as upon an elastic
cushion, the eye rests.

53. The protection of the eyeball against injury? The overhanging brow?
The opening for the optic nerve ?

200

THE SPECIAL SENSES.

FIG. 47.— FRONT VIEW op RIGHT EYE.
(Natural Size.)

1. The Lachrymal, or tear gland, lying be-
neath the upper eyelid.

2. The Nasal Duct is shown by the dotted
line. The * marks the orifice iu the lower
lid.

The central black spot is the pupil; sur-
rounding it is the iris ; and the triangular
white spaces are the visible portion of the
sclerotic.

54. The Eyelids. — The eyelids are two movable cur-
tains, or folds, which, when shut, cover the front part of

the orbit, and hide the
eye from view. The up-
per lid is the larger, has a
curved margin, and moves
freety, while the lower lid
is comparatively short
and straight, and has but
a slight degree of motion
(Fig. 47). Skin covers
the exterior of the lids,
while a fine mucous
membrane lines their in-
ner surface, and is like-
wise spread out over the
entire front of the eye-
ball. This membrane,
which is called the Conjunctiva, is highly sensitive, and
thus plays an important part in protecting the eye against
the lodgment of sand, ashes, chaff, and other foreign parti-
cles that are blown about in the air. This sensitive mem-
brane will not endure the presence of these particles. If
any find access, it causes a constant winking, a flow of
tears, and other signs of irritation, until it is removed.

55. The long, silky eyelashes, which garnish the edges
of the lids, act like a sieve to prevent the entry of dust and
the like; and together with the lids, they regulate the
amount of light which is permitted to enter the eye, so that
it is shielded from a sudden flood or glare of light. The little
points seen in the figure just within the line of the lashes,
especially on the lower lid, represent the months of numer-
ous little sebaceous glands (Fig. 48, D,D), such as are always

54. What are the eyelids? The upper lid? The lower one? The mucous
membrane of the eye ?

55. The eyelashes? The little points within the line of the lashes ? Of what
use are these glands ?

THE SPECIAL SENSES. 201

found in the neighborhood of hairs. These glands supply
a thick, oily material which greases the edges of the lids
and prevents their adhering together, and likewise prevents
the overflow of the tears upon the cheek.

56. The Lachrymal Fluid, or the Tears. — Just
within the outer part of the bony arch cf the brow, where
the bone may be felt to be sharper than in other positions,
is lodged a little organ called the lachrymal gland, the sit-
uation of which is indicated in Fig. 47, 1. This is the
gland whence flows the watery secretion, commonly called
the tears, which is designed to perform an exceedingly im-
portant duty in lubricating the lids, and in keeping the
exposed surface of the eyeball moist and transparent. For,
without this or some similar liquid, the front of the eye
would speedily become dry and lustreless, like that of a
fish which has been removed from the water : the simple
exposure of the eye to the air would then suffice to destroy
vision.

57. This secretion of the tears takes place at all times,
during the night as well as the day; but it is seldom
noticed, except when under the influence of some strong
mental emotion, whether of sorrow or happiness, it is
poured forth in excess, so as to overflow the lids. Strong
light or a rapid breeze will, among many other causes, ex-
cite the flow of the tears. That portion of this secretion
which is not used in moistening the eye is carried off
into the nose by a canal situated near the inner angle of
the eye, called the nasal duct. This duct is shown in Fig.
47, 2, and is connected with each lid by delicate tubes,
which are indicated by dotted lines in the figure ; the as-
terisk marks the little opening in the lower lid, by which
the tears enter the nasal duct. By gently turning the
inner part of that lid downward, and looking in a mirror,

56. The location of the lachrymal gland ? The use of the gland ?

57. When does the secretion of the tears occur? The secretion not used for
the eye? Location of the nasal duct? Its use? The overflow of tears in old
people ?

9*

202

THE SPECIAL SENSES.

this small "lachrymal point'' may be seen in your own
eye. In old people, these points become everted, and do
not conduct the tears to the nasal cavity, so that they are
inconvenienced by an overflow of tears upon the face.

58. Thus we observe that the gland which forms the
tears is placed rt the outer part of the eye, while their
means of exit is at the inner angle of the eye; which fact
renders it necessary that this watery fluid shall pass over
the surface of the eyeball before it can escape. This ar-

FIG. 48.— VERTICAL SECTION OF THE EYE. (Enlarged.)

C, The Cornea.

A, The Aqueous Humor.
I. The Iris*.

P, The Pupil.

L, The Crystalline Lens. '

H, The Ligament of the Lens.

B, The Ciliary Process.

V, The Cavity containing the Vit-
reous Humor.
S, The Sclerotic.

Ch, The Choroicl.

R, The Retina.

N. The Optic Nerve.

DD. The Eyelids.

X, The Levator Muscle of the Upper

Lid.
Y, The Upper Straight Muscle of the

Eye.
Z, The Lower Straight Muscle.

rangement cannot be accidental, but evinces design, for it
thus secures the perfect lubrication of the surface of the
eve, and cleanses it from the smaller particles of dust

58. The watery fluid passing over the eyeball ? Design of the arrangement ?
Winking ?

THE SPECIAL SENSES. 203

which may enter it, in spite of the vigilance of the lids
and lashes. The act of winking, which is generally un-
consciously performed, and which takes place six or more
times in a minute, assists this passage of the tears across
the eye, and is especially frequent when the secretion is
most abundant.

59. The Eyeball. — The remarkable optical instru-
ment called the eyeball, or the globe of the eye, upon
which sight depends, is, as the name indicates, spherical in
shape. It is not a perfect sphere, since the front part pro-
jects somewhat beyond the rest, and at the posterior part
the optic nerve (Fig. 48, N) is united to it, resembling the
junction of the stem with a fruit. In its long diameter,
that is, the horizontal or from side to side, it measures a
little more than an inch; in other directions it is rather
less than an inch. In structure, the ball of the eye is firm,
and its tense round contour may in part be felt by pressing
the fingers over the closed lids.

60. The eyeball is composed chiefly of three internal,
transparent media, called humors; and three investing
coats, or tunics. The former are the aqueous humor, Fig.
48, A, the crystalline lens L, and the vitreous humor v.
Of these the lens alone is solid. The three coats of the
eyeball are called the sclerotic s, the choroid CH, and the
retina R. This arrangement exists in respect to five-sixths
of the globe of the eye, but in the anterior one-sixth, these
coats are replaced by the cornea c, which is thin and trans-
parent, so that the rays of light pass freely through it, as
through a clear window-pane.

61. In shape, the cornea is circular and prominent,
resembling a miniature watch-glass, about -fa of an inch
thick. In structure, it resembles horn (as the name signi-
fies), or the nail of the finger, and is destitute of blood-

59. Describe the shape of the eyeball. Its structure.

GO. Of what is the eyeball composed * State how.

6 1 . The shape of the cornea ? Its structure ? The " white of the eye ?'

204 THE SPECIAL SENSES.

vessels. The Sclerotic (from scleros, hard) is composed of
dense, white fibrous tissue, and gives to the eyeball its
firmness of figure and its white color.; in front, it consti-
tutes the part commonly called "the white of the eye."
It is one of the strongest tissues in the body ; it possesses
very few vessels, and is not very sensitive. It affords pro-
tection to the extremely delicate interior parts of the eye;
and the little muscles which effect its movements are in-
serted into the sclerotic a short distance behind the cornea
(see Fig. 48, Y, z). It is perforated posteriorly to admit the
optic nerve.

62. The Choroid is the second or middle coat of the eye-
ball, and lies closely attached to the inner surface of the
sclerotic. Unlike the latter tunic, its structure is soft and
tender, it is dark in color, and possesses a great abundance
of blood-vessels. Its dark color is due to a layer of dark
brown or chocolate-colored cells spread out over its inner
surface. This dark layer serves to absorb the rays of light
after they have traversed the transparent structures in
front of it ; if the rays were reflected from side to side
within the eye, instead of being thus absorbed, confused
vision would result from the multitude of images which
would be impressed upon the optic nerve.

63. This mechanism has been unconsciously imitated by
the opticians, who, when they make a microscope or tele-
scope, take care that the interior of its tube shall be coated
with a thick layer of black paint or lamp-black; for with-
out it, a clear delineation of the object to be viewed is im-
possible. The albinos, in whom these dark cells of the
choroid are wanting, have imperfect vision, especially in
the daytime and in strong lights. The dark cells are also
wanting in white rabbits, and other animals that have red
or pink eyes ; their vision appears to be imperfect in the
presence of a bright light.

62. The second or middle coat of the eyeball ? Its dark color ?

63. Similar mechanism in microscopes ? The albinos ? White rabbits?

THE SPECIAL SENSES. 205

64. The Iris. — Continuous with the choroid, in the front
part of the globe of the eye, is a thin, circular curtain,
which occasions the brown, blue, or gray color of the eye
in different individuals. On account of the varieties of its
color, this membrane has received the name Iris, which is
the Greek word for "rainbow" (see Fig. 48, i). A front
view of it is shown in Fig. 47. The iris is pierced in its
centre by a round opening, called the pupil (P), which is
constantly varying in size. In olden times it was spoken
of as the " apple of the eye." The hinder surface of the
iris, except in albinos, has a layer of dark coloring matter
resembling that of the choroid. The iris is a muscular
organ, and contains two distinct sets of fibres; one of which
is circular, while the other radiates outward from the pupil.
The action of these sets of fibres regulates the size of the
pupil ; for when the circular set acts, the pupil contracts,
and when the other set acts, the opening expands. Their
action is involuntary, and depends on the reflex system of
nerves, which causes the contraction of the pupil when a
strong light falls upon the eye, and its expansion when
the illumination is feeble.

65. The iris, accordingly, serves a very useful purpose
in regulating the admission of light to the eye. It, how-
ever, does not act instantaneously; and hence, when we
pass quickly from a dark room into the bright sunlight,
the vision is at first confused by the glare of light, but as
soon as the pupil contracts, the ability to see becomes per-
fect. On the other hand, when we enter a dark apart-
ment, such as a cellar, for a short time we can see nothing
clearly ; but as soon as the pupil expands and admits more
light, we are enabled to distinguish the surrounding ob-
jects. Animals of the cat species, and others which prowl
around after nightfall, are enabled to see in the dark by

64. What is the iris ? Its construction ? How is the size of the pupil regu-
lated ?

65. The admission of light to the eye ? The action of the iris under different
circumstances'? The lustre of the eye, how affected in youth and old age ?

206 THE SPECIAL SENSES.

having the iris very dilatable. The size of the pupil affects
the lustre of the eye. When it is large, as it usually is dur-
ing youth, the eye appears clear and brilliant; while in old
age the pupil is small and the eye, is dull. The brilliancy
of the eye is in part, at least, dependent upon the reflec-
tion of light from the front surface of the crystalline lens.

66. Certain poisonous vegetables have the property of
causing the pupil to dilate, and have been used in small
doses to increase the beauty of the eye. One of these
drugs has been so largely used by the ladies for this pur-
pose, that it has received the name belladonna, from the
Italian words meaning " beautiful lady." This hazardous
practice has resulted more than once in the death of the
person desiring thus to increase her personal attraction.
The common English name for belladonna is "deadly
nightshade." (In the diagram on page 214 the shape and
relations of the iris are more accurately shown than in the
figure referred to above.)

67- The Retina constitutes the third and inner coat of
the globe of the eye. This, the important part of the eye
that is sensitive to light, is a kind of nervous membrane,
formed by the expansion of the ultimate filaments of the
optic nerve. Its texture is soft, smooth, and very thin;
it is translucent and of an opaline, or grayish-white
color. It is sensitive to light alone ; and if any form of
mechanical irritation be applied to it, the sensations of
touch and pain are not experienced, but flashes of fire,
sparks, and other luminous appearances are perceived.
Thus an electric shock given to the eye-ball occasions a
flash of light ; and a sudden fall, or a blow upon the eye,
is often apparently accompanied by the vision of "stars."

68. These phenomena are due to what is termed the

66. Means used to increase the beauty of the eye ? The injurious conse-
quences *

67. What part does the retina constitute ? How formed? Its texture ? Color?
Sent" itiveness ?

68. Specific energy of the optic nerve ? Trial in Germany ?

THE SPECIAL SENSES. 207

" specific energy" of the optic nerve, which nerve, in com-
mon with the other nerves of special sense, obeys a general
law of nature, which requires that, whenever one of these
nerves is stimulated, it shall respond with the sensation
peculiar to itself. These flashes of retinal light have no
power to illuminate external objects, although the opposite
of this statement has been maintained. On the occasion
of a remarkable trial in Germany, it was claimed by a per-
son who had been severely assaulted on a very dark night,
that the flashes of light caused by repeated blows upon the
head enabled him to see with sufficient distinctness to
recognize his assailant. But the evidence of scientific
men entirely refuted this claim, by pronouncing that the
eye, under the circumstances named, was incapacitated foi
vision. Too intense light occasions a feeling of pain, but
it is of a peculiar kind, and is termed "dazzling."

69. All parts of the retina are not equally sensitive, and
singularly enough, the point of entry of the nerve of sight,
in the back part of the eyeball, is entirely insensible to light,
and is called the "blind spot." The existence of this point
may be proven by a simple experiment. Hold the accom-

FIG. 49.

panying figure, on page 207, directly in front of and paral-
lel with the eyes. Close the left eye, and fix the, sight
steadily on the left-hand circle ; then, by gradually varying
the distance of the figure from the eye, at a certain dis-
tance (about six inches), the right-hand circle will disappear,

69. Sensitiveness of all parts of the retina ? Experiment to prove the exist-
ence of the "blind spot.1'

208 THE SPECIAL SENSES.

but nearer or further than that, it will be plainly seen.
The other eye may be also tried, with a similar result : if
the gaze be directed to the right-hand circle, the left one
will seem to disappear. The experiment may be repeated
by using two black buttons on the marble top of a bureau,
or on some other white surface. The blind spot does not
practically interfere with vision, since the eye is seldom
fixed immovably on an object, and the insensitive parts of
the two eyes can never be directed upon the same object at
the same time.

70. Impressions made upon the retina are not at once
lost, but persist a measurable length of time, and then
gradually fade away. Thus, a bright light or color, gazed
at intently, cannot be immediately dismissed from sight by
closing or turning away the eyes. A stick lighted at one
end, if whirled around rapidly in the dark, presents the
appearance of an unbroken luminous ring; and the spokes
of a rapidly revolving carriage-wheel seem to be merged
into a plane surface. If an object move too rapidly to pro-
duce this sort of lasting impression, it is invisible, as in1 the
case of a cannon-ball passing through the air in front of
us.

71. If a card, painted with two primary colors— as red and
yellow — be made to rotate swiftly, the eye perceives neither
of them distinctly ; but the card appears painted with their
secondary -color — orange. The average duration of retinal
images is estimated at one-eighth of a second ; and it is
because ihey thus endure, that the act of winking, which
takes place so frequently, but so quickly, is not noticed and
does not interrupt the vision. The retina is easily fatigued
or deprived of its sensibility. After looking steadfastly at
a bright light, or at a white object on a black ground, a
dark spot, corresponding in shape to the bright object,

70. Duration of impressions upon the retina ? How illustrated ?

71. What further illustration? Winking, why it is not noticed. Ease wit'
which the retina is fatigued or deprived of sensibility ? How shown ?

THE SPECIAL SENSES. 209

presents itself in whatever direction we look. This spot
passes away as the retina resumes its activity.

72. If a bright color be gazed at intently, and the eyes
then be turned to a white surface, a spot will appear ; but
its color will be the complement of that of the object. Fix
the eye upon a red wafer upon a white ground, and on re-
moving the wafer a greenish spot of the same shape takes
its place. This result happens because a certain portion of
the retina has exhausted its power to perceive the red ray,
and perceives only its complementary ray, which is green.
The color thus substituted by the exhausted retina is called
a physiological or accidental color. In some persons the
retina is incapable of distinguishing different colors, when
they are said to be affected with " color-blindness." Thus,
red and green may appear alike, and then a cherry-tree,
full of ripe fruit, will seem'bf the same color in every part.
Railroad accidents have occurred because the engineer of
the train, who was color-blind, has mistaken the color of a
signal.

73. The Crystalline Lens.— Across the front of the
eye, just behind the iris, is situated the Crystalline lens,
enclosed within its own capsule. It is supported in its
place partly by a delicate circular ligament, and partly by
the pressure of adjacent structures. It is. colorless and per-
fectly transparent, and has a firm but elastic texture. In
shape it is doubly convex, and may be rudely compared to
a small lemon-drop. The front face of the lens is flatter
than the other, and is in contact with the iris^near its
pupillary margin, as is represented in the diagram on page
214. It is only one-fourth of an inch thick.

74. When this little body becomes opaque, and no longer
affords free passage to the rays of light, as often happens

72. How further shown? How is the result accounted for? " Color-blind-
ues»B ?"

73. The location of the crystalline lens? How supported? Its color and
texture? Shape? Size?

Y4. Cataract? Aqueous humor ? Vitreous humor ?

210 THE SPECIAL SENSES.

with the advance of age, an affection termed " cataract" is
produced. Between the crystalline lens and the cornea is
a small space which contains the aqueous humor (see Fig.
48, A). This humor consists of five or six drops of a clear,
colorless liquid very much like water, as its name implies.
That part of the globe of the eye lying behind the lens is
occupied by the vitreous humor, so called from its fancied
resemblance to melted glass (Fig. 48, v). This humor is a
transparent, jelly-like mass, enclosed within an exceed-
ingly thin membrane. It lies very closely applied to the
retina, or nervous membrane of the eye, and constitutes
fully two-thirds of the bulk of the eyeball.

75. The Uses of the Crystalline Lens. — A con-
vex lens has the property of converging the rays of light
which pass through it ; and the point at which it causes

FIG. 50.— THE RETINAL IMAGE.

them to meet is termed its focus. If a lens of this descrip-
tion, such as a magnifying or burning-glass, be held in
front of an open window, in such a position as to allow
its focus to fall upon a piece of paper, it will be found to
depict upon the paper a miniature image of the scene out-
side of the window. It will be further noticed that the
image is inverted, or upside down, and that the paper

75. What is a lens and its focus ? The miniature image, how produced T

THE SPECIAL SENSES.

at the place upon which the image is thrown is much
brighter than any other part.

76. Now all the transparent structures of the eye, but
especially the crystalline lens, operate upon its posterior
part, or retina, as the convex lens acts upon the paper ; that
is, they paint upon the retina a bright inverted miniature
of the objects that appear in front of the eye (Fig. 50).
That this actually takes place may be proved by experi-
ment. If the eyeball of a white rabbit, the walls of which
are transparent, be examined while a lighted candle is held
before the cornea, an image of the candle-flame may be
seen upon the retina.

77. The form and structure of the crystalline lens endow
it with a remarkable degree of refractive power, and en-
able it to converge all the rays of light that enter it
through the pupil, to a focus exactly at the surface of the
retina. When this lens is removed from the eye, as is
frequently done for the cure of cataract, it is found that
the rays of light then have their focus three-eighths of an
inch behind the retina; that the image is four times larger
than in the healthy eye, that it is less brilliant, and that
its outline is very indistinct. From this we learn that one
of the uses of the crystalline lens is to make the retinal
image bright and sharply-defined, at the same time that it
reduces its size. Indeed, the small size of the image is a
great advantage, as it enables the limited surface of the
retina to receive, at a glance, impressions from a consider-
able field of vision.

78. As the image upon the retina is inverted, how does
the mind perceive the object in its true, erect position ?
Many explanations have been advanced, but the simplest
and most satisfactory appears to be found in the fact that

76. How are figures painted upon the retina ? How proved ?

77. What can be said in respect to the form and structure of the crystalline
lens?

78. How is the inverted image upon the retina presented in its true position to
the mind?

212 THE SPECIAL SENSES.

the retina observes no difference, so to speak, between the
right and left or the upper and lower positions of objects.
In fact, the mind is never conscious of the formation of a
retinal image, and until instructed, has no knowledge that
it exists. Consequently, our knowledge of .the relative
location of external objects must be obtained from some
other source than the retina. The probable source of this
knowledge is the habitual comparison of those objects with
the position of our own bodies: thus, to see an elevated
object, we know we must raise the head and eyes ; and to
see one at our right hand, we must turn the head and eyes
to the right.

79. Long-sight or Hyperopia, and Short-sight
or Myopia. — The eye is not in all cases perfectly
formed. For example, persons may from birth have the
cornea too prominent or too flat, or the lens may be too
thick or too thin. In either of these conditions sight will

Fro. 51.— THE DIFFERENT SHAPES OF THE GLOBE OF THE EYE.

N, The Natural Eye. M, The Short-sighted Eye.

H, The Long-sighted Eye. S, Parallel Rays from the Sun.

be more or less defective from the first, and the defect will
not tend to disappear as life advances. The most common
imperfection, however, is in the shape of the globe ; which
may be short (Fig. 51, H), as compared with the natural
eye, N, or it may be too long, M.

80. When the globe is short, objects can only be clearly

79. The uniform perfection of the eye? Examples? The most common im-
perfection ?

80. How is " long-sight"1 explained? "Short-sight?"

THE SPECIAL SENSES. 213

seen that are at a distance, and the condition of the vision
is known as "long-sight," or hyperopia. It will be ob-
served, by reference to Fig. 51, that the focus of the
rays of light would fall behind the retina of this eye.
When the globe is too long, objects can only be clearly seen
that are very near to the eye; and the condition resulting
from this defect is termed " short-sight," or myopia. The
focus of the rays of light is, in this case, formed in the
interior of the eye in front of the retina.

81. Long-sight, or hyperopia, is common among school-
children, nearly as much so as short-sight, and must not be
confounded with the defect known as the " far sight" of
old people; although in both affections the sight is im-
proved by the use of convex glasses. Children not infre-
quently discover that they see much better when they
chance to put on the spectacles of old persons. For the
relief of short-sight, concave glasses should be employed;
as they so scatter the rays of light as to bring the focus to
the retina, and thus cause the vision of remote objects
to become at once distinct. That form of "squint," in
which the eyes are turned inward, is generally dependent
upon long-sight, while that rarer form, when they turn
outward, is due to short-sight.

82. The Function of Accommodation. — If, after
looking through an opera-glass at a very distant object, it
is desired to view" another nearer at hand, it will be found
impossible to obtain a clear vision of the second object un-
less the adjustment of the instrument is altered ; which is
effected by means of the screw. If an object, like the end of
a pencil, be held near the eye, in a line with another object
at the other side of the room, or out of the window, and
the eye be fixed first apon one and then upon the other, it
will be found that when the pencil is clearly seen, the fur-
si. Lone-sight, how common ? With what must it not be con ounded ? Kind

of jrlasse* for efiort-fight ? Why ? Squint ?

82. What is- stated in connection with the opera-glass? Experiment with
pencil and distant object ?

214 THE SPECIAL SENSES.

ther object is indistinct; and when the latter is seen
clearly, the pencil appears indistinct ; and that it is im-
possible to see both clearly at the same time. Accordingly,
the eye must have the capacity of adjusting itself to dis-
tances, which is in some manner comparable to the action
of the screw of the opera-glass.

83. This, which has been called the function of accom-
modation, is one of the most admirable of all the powers
of the eye, and is exercised by the crystalline lens. It
consists essentially in a change in the curvature of the
front surface of the lens, partly through its own elasticity,
and partly through the action of the ciliary muscle.

FIG. 52.— THE FUNCTION OP ACCOMMODATION.

The right half of the diagram shows the eye at rest. The left half shows the lens
accommodated for near vision.

When the eye is at rest, that is, when accommodated for a
distant object, the lens is flatter and its curvature dimin-
ished (see Fig. 52) ; but when strongly accommodated for
near vision the lens becomes thicker, its curvature in-
creases, and the image on the retina is made more sharp
and distinct. Since a strong light is not required in view-
ing near objects, the pupil contracts, as is shown in the
left-hand half of the diagram.

83. Function of accommodation ? Tn what does it consist ? How is the func-
tion explained ?

THE SPECIAL SENSES.

84. Old-sight, or Presbyopia. — But this marvel-
lously beautiful mechanism becomes worn with use; or,
more strictly speaking, the lens, like other structures of the
body, becomes harder with the approach of old age. The
material composing the lens becomes less elastic, the power
to increase its curvature is gradually lost, and as a conse-
quence, the person is obliged to hold the book further away
when reading, and to seek a stronger light. In a word, the
function of accommodation begins to fail, and is about the
first evidence that marks the decline of life. By looking at
the last preceding diagram, and remembering that the in-
creased curvature of the lens cannot take place, it will be
at once understood why old-sight is benefitted in near
vision by the convex lens, such as the spectacles of old
people contain. It acts as a substitute for the deficiency
of the crystalline lens.

85. The Sense of Hearing. — Sound. — Hearing, or
audition, is the special sense by means of which we are
made acquainted with sound. What is sound? It is an
impression made upon the organs of hearing, by the vibra-
tions of elastic bodies. This impression is commonly prop-
agated by means of the air, which is thrown into delicate
undulations, in all directions from, the vibrating sub-
stance. When a stone is thrown into smooth water, a wave
of circular form is set in motion, from the point where the
stone struck, which constantly increases in size and dimin-
ishes in force, as it advances.

86. Somewhat resembling this, is the undulation, or
sound-wave, which is imparted by a sonorous vibration to
the surrounding atmosphere. Its shape, however, is spher-
ical, rather than circular, since it radiates upward, down-
ward, and obliquely as well as horizontally, like the wave

84. Change of sight with the approach of old age ? Explain the change ?

85. Hearing or audition? What is sound? How propagated commonly.'
Stone thrown in water?

86. Sound-wave in the atmosphere? Its shape? Rate of motion ? Sound, in
water, air, and solid bodies ?

216 THE SPECIAL SENSES.

in water. The rate of motion of this spherical wave of
air is about 1050 feet per second, or one mile in five
seconds. In water, sound travels four times as fast as in
air, and still more rapidly through solid bodies ; along an
iron rod, its velocity is equal to two miles per second.

87. The earth, likewise, is a good conductor of sound.
It is said that the Indian of our western prairies can, by
listening at the surface of the ground, hear the advance of
a troop of cavalry, while they are still out of sight, and
can even discriminate between their tread and that of a
herd of 'buffaloes. Solid substances also convey sounds
with greater power than air. If the ear be pressed against
one end of a long beam, the scratching of a pin at the,
other extremity may be distinctly heard, which will not be
at all audible when the ear is removed from the beam.
Although air is not the best medium for conveying sound,
it is necessary for its production. Sound cannot be pro-
duced in a vacuum, as is shown by ringing a bell in the
exhausted receiver of an air-pump, for it is then entirely
inaudible. But let the air be readmitted gradually, then
the tones become more and more distinct, and when the
receiver is again full of air, they will be as clear as usual.

88. All sonorous bodies do not vibrate with the same
degree of rapidity, and upon this fact depends the pitch of
the sounds that they respectively produce. The more fre-
quent the number of vibrations within a given time, the
higher will be the pitch ; and the fewer their number, the
lower or graver will it be. Now, the rate of the successive
vibrations of different notes has been measured, and it has
thus been found that if they are less than sixteen in a
second, no sound is audible; while if they exceed 60,000
per second the sound is very faint, and is painful to the

87. The earth as a conductor of sound ? To what has the western Indian been
tautrht ? Solid substances as conductors ? As regards sound, in what respect is
air necessary ? Sound in a vacuum ?

THE SPECIAL SENSES. 21?

ear. The extreme limit of the capacity of the human ear
maybe considered as included between these points; but
the sounds which we ordinarily hear are embraced be-
tween 100 and 3,000 vibrations per second.

89. The ear, which is the proper organ of hearing, is the
most complicated of all the structures that are employed
in the reception of external impressions. The parts of
which it is composed are numerous, and some of them are
extremely small and delicate. Nearly all these parts are
located in an irregularly shaped cavity hollowed out in the
temporal, or " temple," bone of each side of the head.
That part of the bone in which the auditory cavity is
placed has the densest structure of all bones of the body,
and has therefore been called the "petrous," or rocky part
of the. temporal bone. In studying the ear, it is necessary
to consider it as divided into three portions, which are
called, from their relative positions, the external ear, the
middle ear, and the internal ear. (In the diagram, Fig. 53,
A, the first is not shaded, the second is lightly shaded, and
the last has a dark background.)

90. The External Ear. — The external portion of the
organ of hearing, designated in Fig. 53, A, includes, first,
that outer part (a), which is commonly spoken of as "the
ear," but which in fact is only the portal of that organ ;
and, secondly, the auditory canal (b). The former consists
of a fiat flexible piece of cartilage, projecting slightly from
the side of the head, attached to it by ligaments, and sup-
plied with a few weak muscles. Its surface is uneven, and
curiously curved, and from its resemblance to a shell, it
has been called the concha. It probably serves to collect
sounds, and to give them an inward direction ; although
its removal is said not to impair the acuteness of hearing
more than a few days.

9O. Of what docs the external portion of the organ of hearing consist? De-
scribe the portal of that organ known as the ear. Its use ?

218 THE SPECIAL SENSES.

;.

91. In those animals whose hearing is more delicate
than that of man, the corresponding organ is of greater
importance, it being larger and supplied with muscles of
greater power, so that it serves as a natural kind of ear-
trumpet, which is easily movable in the direction of any
sonnd^that attracts the attention of the animal. Bold,
predaceous animals generally have the concavity of this

FIG. 53.— THE EAR AND ITS DIFFERENT PARTS.

A. Diagram of the Ear.

a, b. External Ear. d. Middle Ear.

c, Membrane tympani. e. Internal Ear.

B to B"'. Bones of the Middle Ear (magnified).
C, The Labyrinth?, or Internal Ear (highly magnified).

organ directed forward, while in timorous animals, like the
rabbit, it is directed backward. Fishes have no outer ear,
but sounds are transmitted directly through the solid bones
of the head, to the internal organ of hearing.

92. The auditory canal (Fig. 53, A, b), which is con-
tinuous with the outer opening of the ear, is a blind pas-
sage, an inch and a quarter in length, its inner extremity
being bounded by a closely-fitting, circular membrane.
This canal is of oval form, is directed forward and inward,

91. The car in the animate of delicate hearing! Kabbit? Fishes?

92. What is the auditory canal ? Describe it.

THE SPECIAL SENSES. 219

and is slightly curved; so that the inner end is ordinarily
concealed from view. The pouch of the skin which lines
this passage is smooth and thin, especially at the lower
end, where it covers the membrane just mentioned.

93. As in the case of the nostrils, a number of small,
stiff hairs garnish the margin of the auditory canal, and
guard it, to some extent, against the entrance of insects
and other foreign objects. The skin, too, covering its outer
half, is furnished with a belt of little glands which secrete
a yellow, viscid, and bitter substance, called " ear-wax,"
which is especially obnoxious to small insects. As the
outer layer of this wax-like material loses its useful pro-
perties, it becomes dry, and falls out of the ear in the form
of minute, thin scales, a fresh supply being furnished from
the little glands beneath. In its form, the auditory canal
resembles the tube of an ear-trumpet, and serves to convey
the waves of sound to the middle portion of the ear.

94. The Middle Ear, or Tympanum. — The middle
ear is a small cavity, or chamber, of irregular shape, about
one-fourth of an inch across from side to side, and half an
inch long (see Fig. 53, A, d). From the peculiar arrange-
ment of its various parts it has very properly been called
the tympanum, or the "drum of the ear." The middle
ear, like the external canal, contains air.

95. The circular membrane, already mentioned as clos-
ing the auditory canal, is the partition which separates
the middle from the external ear, and is called the mem-
brana tympani (c), and may be considered as the outer head
of the drum of the ear. It is sometimes itself spoken of as
the " drum," but this is incorrect ; since a drum is not a
membrane, but is the hollow space across which the mem-
brane is stretched. This membranous drum-head is very
tense and elastic, and so thin as to be almost transparent;

93. How i* it guarded and protected ? Ear-wax ?

94. What is the middle ear 'i Why called tympanum ?

95. What, is the membraua tympani ? Describe: it.

220 THE SPECIAL SENSES.

its margin is fastened into a circular groove in* the adjacent
bone. Each wave of sound that impinges against this
delicate membrane causes it to vibrate, and it, in turn,
excites movements in the parts beyond.

96. Within the tympanum is arranged a chain of re-
markable " little bones," or ossicles. They are chiefly three
in number, and from their peculiar shapes bear the follow-
ing names: malleus, or the mallet; incus, or the anvil;
and stapes, or the stirrup. A fourth, the smallest bone in
the body, in early life intervenes between the incus and
stapes, but at a later period it becomes a part of the incus.
It is called the orbicular bone. Small as are these ossicles —
and they, together, weigh only a few grains — they have
their little muscles, cartilages, and blood-vessels, as per-
fectly arranged as the larger bones of the body. One end
of the chain of ossicles, the mallet, is attached to the mem-
brane, of the tympanum, or outer drum-head, while the
other end, the stirrup, is firmly joined by its foot-piece to
a membrane in the opposite side of the cavity. The chain,
accordingly, hangs suspended across the drum between the
two membranes ; and when the outer one vibrates under
the influence of the sound-wave, the chain swings inward
and transmits the vibration to the entrance of the inner
ear.

97. The musical instrument, the drum, is not complete
if the air within be perfectly confined : we therefore find in
all instruments of this kind a small opening in the side,
through which air may pass freely. By this means the
pressure of the air upon the vellum which forms the head
of the drum is made equal upon all sides, and the resonance
of the drum remains unaffected by the varying density of
the atmosphere. It will, therefore, emit its proper sound,
whether it be struck in the rarified air of the mountain-
top, or in the condensed air of a mine. The tympanum,

96. What are the ossicles ? Their number and names ? Their arrangement ?

97. The Eustachian tube ? Describe it, and state its use.

THE SPECIAL SENSES.

221

or drum of the ear, in like manner has an opening by
means of which it communicates freely with the external
air. This opening is a narrow canal, about an inch and a
half long, called the Eustachian tube, after the name of its
discoverer, Eustachius. _^.

98. The course of this passage is indicated in Fig. 54, i,
directed downward and inward: its other extremity opens
into the upper part of the throat. The passage itself is

FIG. 54.— SECTION or THE RIGHT EAR.

A, The Concha. E, Incus, or Anvil.

B, Auditory Canal. M, Malleus, or Mallet.

C, Membrane of the Drum, I, Eustachian Tube.

(the lower half.) - G, Semicircular Canals.

D, A small muscle. H, Cochlea, or snail's shell.

ordinarily closed, but whenever the act of swallowing or
gaping takes place, the orifice in the throat is stretched
open, and the air of the cavity of the tympanum may then
be renewed. Air may at will be made to enter through
this tube, by closing the mouth and nose, and then trying

98. What can you state of the action of the Eustachian tube ?

222 THE SPECIAL SENSES.

to force air through the latter. When this is done, a dis-
tinct crackle or clicking sound is perceived, due to the
movement of the membranes, and of the little bones of the
ear.

99. The Eustachian tube serves, also, as an escape-pipe
for the fluids which form within the middle ear; and
hence, when its lining membrane becomes thickened, in
consequence of a cold, or sore throat, and the passage is
thus more or less choked up, the fluids are unable to escape
as usual, and therefore accumulate within the ear. When
this takes place, the vibrations of the membrane are inter-
fered with; the sounds heard appear muffled and indis-
tinct; and a temporary difficulty of hearing, which is
known as "throat-deafness," is the result. This result re-
sembles the effect produced by interrupting the vibrations
of a sonorous body, such as all are familiar with ; if the
finger be placed upon a piano-string or bell when it is
struck, the proper -sound is no longer fully and clearly
emitted. But the primary use of this tube is to afford a
free communication between the middle ear and the exter-
nal atmosphere, and thus secure an equal pressure upon
both sides of the membrane of the drum of the ear, however
the density of the atmosphere may vary. If, from undue
tension of the membranes, pain is experienced in the ears,
when ascending into a rare atmosphere, as in a balloon, or
descending into a dense one, as in a diving-bell, it may be
relieved by repeating the act of swallowing, from time to
time, in order that the inner and outer pressure may thus
be promptly equalized.

100. The Internal Ear, or Labyrinth.— The most
essential part of the organ of hearing is the distribution of
the auditory nerve. This is found within the cavity of the
internal ear, which, from its exceedingly tortuous shape,

99. What other purpose does the Eustachian tube serve * How is this shown ?
" Throat-deafness* *" Primary use of the Eustachian tube ?

100. The essential part of the organ of hearing ? Its location ? Formation ?

THE SPECIAL SENSES. 223

has been termed the labyrinth (see Fig. 53, c). This
cavity is hollowed out in dense bone, and consists of three
parts; the vestibule (a), or ante-chamber, which is connected
with the other two ; the cochlea (b), or snail's shell ; and the
three semicircular canals (c). The manner in which the
nerve of hearing is distributed is remarkable, and is pecu-
liar to this nerve. In the vestibule and the canals its
fibres are spread out over the inner surface, not of the bony
cavity but of a membranous bag, which conforms to and
partially fills that cavity; and which floats in it, being
both filled and surrounded with a clear, limpid fluid.

101. A singular addition to the mechanism of hearing is
observed within this membranous bag of the labyrinth
This consists of two small oval ear-stones, and a quantity
of fine powder of a calcareous nature, which is called "£ar-
sand." When examined under the microscope, these sandy
particles are seen to lie scattered upon and among the
delicate filaments of the auditory nerve; and it is probable,
that as the tremulous sound-wave traverses the fluid of the
vestibule, the sand rises and falls upon the nerve filaments,
and thus intensifies the sonorous impression.

102. In, the cochlea, or snail's shell, which contains the
fluid, but no membrane, the nerve ramifies upon a spiral
shelf, which, like the cochlea itself, takes two and a half
turns, growing continuously smaller as it winds upward.
As many as three thousand nerve fibres of different lengths
have been counted therein ; which, it has been thought,
form the grand, yet minutely small key-board, upon which
strike all the musical tones that are destined to be con-
veyed to the brain. The vestibule, it is also supposed, takes
cognizance of noise as distinguished from musical sounds;
while the office of the semicircular canals is, in part at
least, to prevent internal echoes, or reverberations.

101. Where i? the "ear-sand11 found 1 Give the theory as to its use.

102. In the cochlea or snail1* shell ? '-Key-board1' in the internal ear? The
vestibules ? Semicircular canals *>

THE SPECIAL SKN

103. The vestibule communicates with the chain of
bones of the middle ear by means of a small open ing,
called the "oval wfadow," or/emfaa oralis. Across this
window is stretched the membrane, which has already
been alluded to as being joined to the stirrup-bone of the
middle ear. Through this window, then, the sound-wave.
which traverses the external and middle ear, arrives at last
at the labyrinth. The limpid fluid which the latter con-
tains, and which bathes the terminal fibres of the nerve of
hearing, is thus agitated, the nerve-fibres are excited, and
a sonorous impression is conducted to the brain, or, as we
say, a sound is heard.

104. Protection of the Sense of Hearing.— From
what has been seen of the complicated parts which com-
pose the organ of hearing, it is evident that while many
of them possess an exquisite delicacy of structure, Nature
has well and amply provided for their protection. We
have observed the concealed situation of the most impor-
tant parts of the mechanism of the ear, the length of its
cavity, its partitions, the hardness of its Avails, and its
communication with the atmosphere; all these provisions
rendering unnecessary any supervision or care on our part
in reference to the interior of the ear. But in respect to

. ternal parts, which are under our control and within
the reach of harm, it is otherwise. We may both observe
the dangers which threaten them, and learn the means
necessary to protect them.

105. One source of danger to the hearing consists in
lowering the temperature of the ear, especially by the
introduction of cold water into the auditory canal. Every
one is familiar with the unpleasant sensation of distension
and the confusion of sounds which accompany the filling
of the ear with water when bathing: the weight of the

1OS. With what doo* tin- vestibule communicate? What is the theory bv
\\hich sound is conducted to the brain?

104. The formation of the onran of hearing with a view to it* protection?

105. Danger to which tin- hearing may be "subjected ? Ae.\

THE SPECIAL BENSB8, 225

water within it ivally distends tho membrane, and the cold
chills tho adjacent sensitive pans. It is not surprising,
therefore, that the frequent introduction of cold water and
its continued presence in the ear enfeeble the souse of
hearing, (/are >liould ho takon to remove water from the
oar a ft or bathing, by hold ing the head on one side, and,
at the same time, slightly expanding the outer orifice, so
that the ilnid may run out. For a like reason, the hair
about the oars should not be allowed to remain wet, but
should be thoroughly dried as soon as possible.

106. It may be stated as a general rule, to which there
are but tow exceptions, that no cold liquid should ever be
allowed to enter the ear. When a wash or injection is
rendered necessary, it should always be warmed before use.
The introduction of cold air is likewise hurtful, especially
when it pours through a crevice directly into the ear, as it-
may often do through the broken or partially closed win-
dow of a car. The avoidance of this evil gives rise to
Another almost as great ; namely, the introduction of cot-
ton or other soft substances into the ear to prevent it from
"catching cold." This kind of protection tends to make
the part unnaturally susceptible to changes of tempera-
ture, and its security seems to demand the continued pres-
ence of the " warm" covering. As a consequence of its
presence, sounds are not naturally conveyed, and the sen-
sit iveness of the nerve of hearing is gradually impaired.

107. The chief source of injury, however, to the ear is
from the introduction of solid substances into the auditory
canal, with the design of removing insects or other foreign
objects that have found their way into the ear; or with
the design of scraping out the ear-wax. For displacing a
foreign object, it is usually sufficient to syringe the ear
gently with warm water, the head being so held that the

106. The ereneral rnle as to the use of water for the ear?

107. Chief nonrco of injury to the ear? Directions for removing foreign ob-
ject? from the ear ? Of a live insect ?

10*

226

THE SPECIAL SENSES.

fluid; easily escapes. If a live insect has gained entrance
to the ear, it may first be suffocated by pouring a little oil
upon it, and afterward removed by syringing the ear as
just mentioned.

108. The^rp&oval of ear-wax is generally unnecessary;
for, as we havVbefore seen, Nature provides that the excess
of it shall become dry, and then spontaneously fall out in
the form of fine scales. The danger from the introduction
of solid implements into the outer ear is chiefly found in
the fact that the membrane which lies at the bottom of it
is very fragile, and that any injury of it is liable to be per-
manent, and to permanently impair the hearing of the
injured ear.

QUESTIONS FOR TOPICAL REVIEW.

Give a* full statements as yon can on the following subjects :

1. Production of sensation 177, 178

2. Variety of sensations 178, 179

3. General sensibility 179, 180

4. The sensation of pain 180

5. The uses of pain 180, 1S1, 182

6. Special sensation 182, 183

7. Orirans of touch 183. 1.W4

8. The sense of touch 184, 185, 186

9. The delicacy of tonch 186. 1S7

10. Sensations of temperature and

weight 187, 188

11. The orsran of taste 188, 1!^

12. The sense of taste 189, 191

13. Relations of taste, etc 190, 191

14. Influence of education, etc.. 191. 19)

15. The sense of smell 192, 193

16. The nerve of smell 193, 194

17. Uses of the sense of smell. .194, 195
IS. The sense of sight 196, 197

19. Lisrht. and the optic nerve. .197, 198

20. The organ of sight 19S, 199

21. The orbits 199

22. The eyelids 200, 201

23. The lachrymal fluid 201. 202. 203

24. The eyeball 2(3. 204

25. The iiis 2(>5. 206

26. The retina 206, 207, 2( 8. 209

27. The crystalline lens 209, 210

28. Uses of the lens 210,211. 212

29 Lon? and short sight 212, 213

30. Function of accommodatioii.213, 214

31. Old sight, or presbyopia 215

32. Hearing and sound'. ... .215. 216, 217
83. The external ear 217. 218. 219

34. The middle ear 219—222

35. The internal ear 222. 223, "224

36. Protection of the sense of hear-

ing 224, 225, 226

THE VOICE.

CHAPTER XI.

THE VOICE.

Voice and Speech — The Larynx, or Hie Organ of the Voice — The Vovil
Cords— The Laryngoscope— The Production oftJie Voice— The Use
of the Tongue— The different Varieties of Voice— The Change of
Voice — Its Compass— Purity of Tone — Ventriloquy.

1. Voice and Speech. — In common with the majority
of the nobler animals, man possesses the power of uttering
sounds, which are employed as a means of communication
and expression. In man, these sounds constitute the
voice ; in th& animals, they are designated as the cry. The
song of the bird is a modification of its cry, which is ren-
dered possible from the fact that its respiratory function is
remarkably active. The sounds of the animals are gener-
ally, but not always, produced by means of their breathing
organs. Among the insects, they are sometimes produced
by the extremely rapid vibrations of the wings in the act
of flight, as in the case of the musquito ; or they are pro-
duced by the rubbing together of hard portions of the
external covering of the body, as in the cricket. Almost
all kinds of marine animals are voiceless. The tambour-
fish and a few others have, however, the power of making
a sort of noise in the water.

2. But man alone possesses the faculty of speech, or the
power to use articulate sounds in the expression of ideas,
and in the communication of mind with mind. Speech is
thus an evidence of the superior endowment of man, and
involves the culture of the intellect. An idiot, while he

1 . The uttering of sounds by animals ? How produced ?

2. The evidence of man's superior endowment? What is stated of the idiot?
Parrot ? Raven ?

228 THE VOICE.

may have complete vocal organs and full power of uttering
sounds or cries, is entirely incapable of speech ; and, as a rule,
the excellence of the language of any people will be found
to be proportional to their development of brain. Man,
however, is not the only being that has the power to form
articulate sounds, for the parrot and the raven may also
Ibe taught to speak by rote ; but man alone attaches mean-
ing to the words and phrases he employs.

3. Speech is intimately related to the sense of hearing,
A child born deaf is, of necessity, dumb also; not because
the organs of speech are imperfect, for he can utter cries
and may be taught to speak, and even to converse in a
rude and harsh kind of language ; but because ,he can
form no accurate notion of sound. And a person, whose
hearing is not delicate, or as it is commonly expressed,
who "has no ear for music," cannot sing correctly. A per-
son who has impaired hearing commonly talks in an un-
naturally loud and monotonous voice. These examples
show the necessary relation of intelligence and the sense
of hearing with that form of articulate voice, which is
termed speech.

4. The Organ of the Voice.— The essential organ
of the voice is the Larynx. This has been previously
alluded to in its relation to the function of respiration ;
and, in the chapter on that subject, are figured the front
view of that organ (Fig. 35), and its connection with the
trachea, tongue, and other neighboring parts (Fig. 38). It
is situated at the upper part of the neck, at the top of the
trachea, or tube by which air passes into and out of the
lungs. The framework of the larynx is composed of four
cartilages, which render it at once very strong and suffi-
ciently flexible to enable it to move according to the re-
quirements of the voice.

3. Speech and hearing? A deaf child? Person having "no ear for music?1'
Impaired hearincr ? What do the examples show?

4. Orjpin of the voice ? Where situated ? Of what is its framework composed ?

THE VOICE.

5. The names of -the cartilages are (1) the thyroid,
which is a broad thin plate, bent in the middle and placed
in the central line of the front part of the neck, where it
is known as the pomum Adami, or

Adam's apple (Fig. 55, B), and
where it may be felt moving up
and down with each act of swal-
lowing; (2) the cricoid, which is
shaped like a seal ring, with the
broad part placed posteriorly (Fig.
55, E). At the top of the cricoid
cartilage are situated the two small
arytenoid cartilages, the right one
of which is shown in Fig. 55, c.
These latter little organs are much
more movable than the other two,
and are very important in the pro-
duction of the voice. They have
a true ball and socket joint, and
several small muscles which con-
tract and relax with as perfect regu-
larity and accuracy as an-y of the
larger muscles of the body.

6. The interior of the larynx is SECTION °?r™^AulYNX AND
lined with a very sensitive mucous ^;

membrane, which is much more g,
closely adherent to the parts be- f ;
neath than is usually the case with H' The Trachea-
membranes of this description. The epiglottis (A), con-
sisting of a single leaf-shaped piece of cartilage, is attached
to the front part of the larynx. It is elastic, easily moved,
and fits accurately over the entrance to the air-passages
below it. Its office is to guard these delicate passages and
the lungs against the intrusion of food and other foreign

5. Names, formation, and situation of the eartilasres ?

6, Lining of the interior of the larynx ? The epiglottis ?

230 THE VOICE.

articles, when the act of swallowing takes place. It also
assists in modifying the voice.

7. The Vocal Cords. — Within the larynx, and stretched
across it from the thyroid cartilage in front to the aryte-
noid cartilages behind, are placed the two sets of folds,
called the vocal cords. The upper of these, one on each
side, are the false cords, which are comparatively fixed and
inflexible. These are not at all essential to the formation
of vocal sounds, for they have been injured, in those lower
animals whose larynx resembles that of man, without ma-
terially affecting their characteristic cries. Below these,
one on each side, are the true vocal cords (Fig. 55, F),
which pursue a similar direction to the false cords, namely,
from before backward. But they are composed of a highly
elastic, though strong tissue, and are covered with a thin,
tightly-fitting layer of mucous membrane. Their edges
are smooth and sharply defined, and when they meet, as
they do in the formation of sounds, they exactly match
each other.

8. Between the true and false vocal cords is a depression
on each side, which is termed the ventricle of the larynx
(Fig. 55, D). The integrity of these true cords, and their
free vibration, are essential to the formation of the tones
and the modulation of the natural voice. This is shown
by the fact that, if one or both of these cords are injured
or become diseased, voice and speech are compromised;
or when the mucous membrane covering them becomes
thickened, in consequence of a cold, the vocal sounds are
rendered husky and indistinct. When an opening is made
in the throat below the cords, as not infrequently happens
in consequence of an attempt to commit suicide, voice is
impossible except when the opening is closed by external
pressure.

7» Wh«-r(» are the vocal corrl< ? The fnlsc rrtrds? The true cords?
8. Whcni i* the ventricl« of the larynx? The essentials to the formation of the
tones and modulation of the voice ?

THE VOICE. 231

9. The interval or space between the true cords of the
voice is constantly varying, not only when their vocal
function is in exercise, but also during the act of respira-
tion. Every time the lungs are inflated, the space
increases to make wide the entrance for the air; and dimin-
ishes slightly during expiration. So that these little cords
move gently to and fro in rhythm with the expansion and
contraction of the chest in breathing. These movements
and others may be seen to take place, if a small mirror
attached to a long handle be placed back into the upper
part of the throat; the handle near the mirror must be

FIG. 56.
A VIEW or THE VOCAL CORDS BY MEANS op THE LARYNGOSCOPE.

bent at an angle of 45°, so that we may look "around the
corner," so to speak, behind the tongue. The position
which the mirror must assume will be understood by
reference to Fig. 38. A view of what may be seen under
favorable circumstances, during tranquil inspiration is
represented in Fig. 56. The vocal cords are there shown as
narrow, white bands, on each side of the central opening,
and since the image is inverted, the epiglottis appears up-
permost. The rings partly seen through the opening be-
long to the trachea. This little mirror is the essential part

9. Variation in the interval between the true cords of the voice? Experiment
with the mirror ?

232 THE VOICE.

of an instrument, which is called the laryngoscope, and,
simple as it may seem, it is accounted one of the most val-
uable of the recently invented appliances of the medical
art.

10. The Production of the Voice.— During ordi-
nary tranquil breathing no sound is produced in the lar-
ynx, true vocal tones being formed only during forcible
expiration, when, by an effort of the will, the cords are
brought close together, and are stretched so as to be very
tense. The space between them is then reduced to a
narrow slit, at times not more than -ffa °f an ^nc^ in
width ; and the column of expired air being forced through
it causes the cords to vibrate rapidly, like the strings of a
musical instrument. Thus the voice is produced in its
many varieties of tone and pitch; its intensity, or loud-
ness, depending chiefly upon the power exerted in expell-
ing the air from the lungs. When the note is high, the
space is diminished both in length and width ; but when it
is low, the space is wider and longer (Fig. 57, B, c), and
the number of vibrations is fewer within the same period
of time.

FIG. 57.

THE DIFFLUENT POSITIONS OF THE VOCAL CORDS.

• A, The position during inspiration. B, In the formation of low notes.
C, In the formation of high notes.

11. The personal quality of the voice, or that which en-
ables us to recognize a person by his speech, is mainly due
to the peculiar shape of the throat, nose, and mouth, and

10. The formation of true vocal tones ?

1 1 . To what is the personal quality of the voice mainly due ? What aids are
there ?

THE YOICE. 233

the resonance of the air contained within those cavities.
The walls of the chest and the trachea take part in the
resonance of the voice, the air within them vibrating at
the same time with the parts above them. This may be
tested by touching the throat or breast-bone, when a
strong vocal effort is made. The teeth and the lips also
are important, as is shown by the unnatural tones emitted
by a person who has lost the former, or by one who is
affected with the deformity known as "hare-lip." The
tongue is useful, but not indispensable to speech ; the case
of a woman is reported, from whom nearly the whole
tongue had been torn out, but who could, nevertheless,
sneak distinctly and even sing.

'/ 12. The varieties of voice are said to be four in num-
ber ; two, the bass and tenor, belonging to the male sex ;
and two, the contralto or alto, and soprano, peculiar to the
female. The baritone voice is the name given to a variety
intervening between the bass and tenor. In man, the
voice is strong and grave; in woman, soft and high. In
infancy and early youth, the voice is the same in both
sexes, being of the soprano variety : that of boys is both
clear and loud, and being susceptible of considerable train-
ing, is highly prized in the choral services of the church
and cathedral. At about fourteen years of age the voice is
said to change ; that is, it becomes hoarse and unsteady by
reason of the rapid growth of the larynx. In the case of
the girl, the change is not very marked, except that the
voice becomes stronger and has a wider compass ; but in
the boy, the larynx nearly doubles its size in a single year,
the vocal cords grow thicker, longer, and coarser, and the
voice becomes masculine in character. During the prog-
ress of this change, the use of the voice in singing is inju •
dicious.

13. The ordinary range of each of the four varieties of

1 2. Varieties of voice ? The baritone ? The voice in early youth ?

1 3 j The rouge of the voice ? Result of careful training of the vocal organs ?

234 THE VOICE.

the voice is about two octavos; but this is exceeded in the
case of several celebrated vocalists. Madame Parepa-Rosa
has a compass of three full octaves. When the vocal or-
gans have been subjected to careful training, and are
brought under complete control of the will, the tension
of the cords become exact, and their vibrations become
exceedingly precise and true. Under these circumstances
the voice is said to possess "purity" of tone, and can be
heard at a great distance, and above a multitude of other
sounds. The power of a pure voice to make itself heard
was recently exemplified in a striking manner : at a musi-
cal festival held in an audience-room of extraordinary size,
and amid an orchestra of a thousand instruments and a
chorus of twelve thousand voices, the artist named above
also sang ; yet such was the purity and strength of her
voice that its notes could be clearly heard rising above the
vast waves of sound produced by the full accompaniment
of chorus and orchestra.

14. In the production of the articulate sounds of speech,
the larynx is not directly concerned, but those sounds
really depend upon alterations in the shape of the air-
passages above that organ. That speech is not necessarily
due to the action of the larynx is proven by the following
simple experiment. Let an elastic tube be passed through
the nostril to the back of the mouth. Then, while the
breath is held, cause the tongue, teeth, and lips to go
through the form of pronouncing words, and at the same
time, let a second person blow through the tube into the
mouth. Speech, pure and simple, or, in other words, a
whisper is produced. Still further continue the experi-
ment, while permitting vocal sounds to be made, and there
will be produced a loci and whispering speech at the same
moment; thus showing that voice and speech are the re-
sult of two distinct acts. Sighing, in like manner, is pro-

1 4. The production of the articulate sounds ? What experiment is mentioned .»

THE VOICE. 235

duced in the mouth and throat; if, however, a vocal sound
be added, the sigh is changed into a groan.

15. Ventriloquism is a peculiar modification of natu-
ral speech, which consists in so managing the voice that
words and sounds appear to issue, not from the person,
but from some distant place, as from the chimney, cellar,
or the interior of a chest. The original meaning of the
word ventriloquism (that is, speaking from the belly), in-
dicates the early belief that this mode of speech was de-
pendent upon the possession and use of some special organ
besides the larynx and mouth ; but at the present time, it
is known that it is produced by these organs alone, and
that the sources of deception consist on the part of the
performer, in the dexterous management of the voice, to-
gether with a talent for mimicry; and, on the part of the
auditory, in the liability of the sense of hearing to error in
respect to the direction of sounds. The ventriloquist not
only seems to " throw his voice," as it is said, or simulates
the sotind as it usually appears at a distance with but lit-
tle motion of the lips and face, but he imitates the voices
of an infant and of a feeble old man, of a drunken man
disputing with an exasperated wife, the broken language of
a foreigner, the cry of an animal in distress, demonstrating
that the performer must be proficient in the art of mimicry.
Ventriloquism was known to the ancient Eomans and
Greeks ; and it is thought that the mysterious responses
that were said to issue from the sacred trees and shrines
of the oracles at Dodona and Delphi, were really uttered
by priests who had the power of producing this form of
speech.

15. What is ventriloquism ? Indication of the original meaning of the word ?
How are the ventriloquous sounds produced ?

236 THE MICROSCOPE.

CHAPTER XII.

<*

THE USE OF THE MICROSCOPE IN THE STUDY OF
PHYSIOLOGY.

1. The Law of the Tissues. — The will of an infinite
Creator is obeyed by atoms as well as by worlds. He has
seen fit to commit all the functions of life to structures or
tissues so small as to be invisible to the naked eye. A
muscle, for example, as we have already learned, is com-
posed of innumerable filaments, visible only by the aid of
the microscope; and the power of the muscular mass is
but the sum of the contractile power of the filaments
which enter into its composition. Again, each cell of the
liver, invisible to unassisted sight, is a secreting organ, and
the liver performs as much duty as the sum of these mi-
nute organs renders possible and no more.

2. The Necessity of the Microscope. — If, there-
fore, we would know the real structure of the human
body, we must make use of the microscope. We are not at
liberty either to use it or not ; we must have recourse to it
in order to obtain a real knowledge of the human body.
Our eyes are constructed for the common offices of life, to
provide for our wants and guard us from the ordinary
sources of danger ; but by arming them with lenses, the
real structure of plants and animals is revealed to our
intelligence ; and enemies, otherwise invisible, that lie in
wait in the air we breathe, and in our daily food and drink,
to destroy life, are guarded against,

3. Convex lenses, or magnifying glasses, are disks
of glass or other transparent substance, which have the

1 . The will of the Creator, by what obeyed ? The power of a muscle ?
Amount of duty performed by the liver?

2. Necessity for usinjr the microscope ? The advantages gained by its use ?

3. What are convex lenses? Kind of lenses used in microscopes? Experi-
ment ? Picture thrown upon the eye ? Derivation of the word microscope *

THE MICROSCOPE. 237

property of picturing upon the retina of the eye an
image of an object larger than the image produced there
without their aid. The glasses used in microscopes are
either double convex lenses (a) or plano-convex lenses (b).

b

If a double convex lens or a plano-convex one be placed
over a hole in the shutter of a darkened room, or over
the key-hole of a door, and a piece of paper be held at a
proper distance, a picture of all objects in front of the
lens will be thrown on the paper, as in the camera-obscura
or the magic-lantern. Now, in the same manner, a lens
throws a picture of objects to which it is directed on the
retina of the eye, and when*that picture is larger than the
image made in the eye by the object, without the aid of
the lens, it is magnified, or the lens has served as a micro-
scope, so called, from its use in seeing small objects, from
mikros, small, and skopeo, to see.

4. Different Kinds of Microscopes. — Microscopes
are either simple or compound. The glasses of magnifying
spectacles, like those commonly used by aged persons, are
simple microscopes. Magnifying glasses, mounted in
frames such as are for sale by opticians and others, for
the detection of counterfeit money, are simple microscopes,
and are useful in studying the coarser structure of plants
and animals.

5. The most powerful simple microscopes are made by
melting in a flame a thread of spun glass, so as to form a

4. Kinds of microscope ? What are simple microscopes ?

5. Construction of the most powerful simple microscopes? In practice? A
doublet ': Triplet ? Why are compound microscopes superior to simple ones ?

238 THE MICROSCOPE.

minute globule or bead, which, when set in a piece of
metal and used to examine objects on a plate of glass held
up to the light, gives a high magnifying power. In prac-
tice, however, it is found better to use several magnifying
glasses of moderate power, than a simple lens alone of
high power. A combination of two lenses is called a doub-
let—of three, a triplet. All simple microscopes throw an
enlarged image of the object upon the retina. Compound
microscopes are so constructed that the enlarged image of
an object is again magnified by a second lens, and hence
their magnifying power is vastly superior to that of simple
microscopes.

6. The accompanying diagrams will explain the action
of the compound microscope compared with that of the

FIG. 58.— SIMPLE MICROSCOPE.

simple microscope. In Fig. 58, which represents the work-
ing of the simple microscope, the rays from the object (a b),
passing through the lens (L), form an image (a' b') in the
retina of the eye (E), and as all images are inverted in the
eye, the object is seen as all other objects are, and appears
erect. In Fig. 59 is seen the action of the compound
microscope. An inverted image (a' V) of the object (a b)
is magnified by the. second lens (L'), and an erect image is
thrown upon the retina, which, as all other objects seen
erect with the naked eye are inverted, gives to the image
a contrary direction, or inverts it to the mind.

G. Explain, by means of the diagram, the action of the compound microscope.

THE MICROSCOPE.

239

7. A Compound Microscope consists of two por-
tions : the optical portion, or the lenses, and the mechanical
portion, or the instrument which bears

* ,^-3BP» > fv M

the lenses. The glasses of a compound
microscope are two : the object-glass (D),
Fig. 60, and the lower lens of Fig. 59,
and the ocular or eye-piece (A), Fig. 60,
and the upper piece of Fig. 59. Both
the object-glass and the eye-piece may,
and usually do, consist of more than
one lens, for, as previously mentioned,
better results are obtained by a com-
bination of lenses of moderate power
than by single lenses of high power
and great curvature.

8. How to choose and use a
Microscope. — No attractiveness in
the mechanical part of a microscope
can compensate for inferior lenses;
and the very first consideration in the
choice of an instrument should be the
excellence of the optical part of the
instrument. In the use of the instru-
ment, care should be exercised to keep
the lenses clean, free from dust, not to
press the object-glass upon the object
under observation, and not to wet it
in the water in which most objects are
examined. A good microscope re-
quires its own table ; and when not
in use, should be covered by a bell
glass or a clean linen cloth.

9. The mechanical portion of the instrument varies

7, Portions, in a compound microscope ? The glasses ?

8. How to choose a microscope ? How to use it?

il. The characteristics of the best instrument? What special requisites should
be insisted upon ? Why, as to a horizontal stage ?

FIG. 59.
COMPOUND MICROSCOPE.

240

THE MICROSCOPE.

greatly in different instruments. That one is the best
which is simplest, the most solid and easily managed.
The stage (E), upon which the object is pla?3<i> should

A, Eye-piece.

B, Body.

C, Collar.

D, Object-glass.

FIG

E, Stage.

F, Hinire.

G, Mirror.
H, Stand.

not be movable : it should be solid and firm. The
screw by which the focal distance is adjusted, and which

THE MICROSCOPE.

241

is in constant use, should be so placed that it can be
worked by the hand resting on the table: otherwise fa-

FIG. 61.

tigue is soon induced. The direction of the tube carry-

11

242 THE MICROSCOPE.

ing the glasses should be perpendicular, and the stage
therefore horizontal. Most objects in human anatomy are
examined in Avater or in other liquids, or they are them-
selves liquids; hence an oblique stage is often incon-
venient.

10. Additional Apparatus. — As almost all objects
in human anatomy are examined by transmitted light
thrown up from the mirror (G, Fig. 60) beneath the stage
through the object to the eye, they must be placed upon
strips of clear glass about three inches long and one inch
wide, commonly called '''slides." These should be pro-
cured with the microscope. Again, most objects seen with
high powers require to be covered with a thin plate of
glass, very properly called a " cover," that the moisture of
the specimen may not tarnish the object-glass. Square or
circular covers of very thin glass are therefore provided ;
and a good supply of these should be always on hand.
These glasses should be kept in a covered dish filled with
a mixture of alcohol and water. Simple water will not re-
move the fatty matter which exists in all animal tissues,
and, therefore, the glasses cannot be thoroughly cleaned
with it alone.

11. When glasses are required for use, they should be
removed from the liquid and wiped clean and dry with a
soft linen handkerchief. Delicate knives, scissors, needles
mounted in handles, forceps, pipettes or little tubes for
taking up water, should be obtained; these are essential to
all microscopical study. The table should be supplied with
glass-stoppered bottles containing the various liquids or-
dinarily used in the study of physiology. Thus, tincture
of iodine is indispensable in studying vegetable structure,
acetic acid in the study of animal tissues; and other articles
will have to be added from time to time, as your progress
in study demands them.

10. Slides ? Covers, square and circular? How kept?

11. Cleaning the glasses ? Knives, scissors, etc. ? various liquids?

THE MICROSCOPE. 243

12. Preliminary Studies. — In order to prepare the
way for the study of any department of science with the
aid of the microscope — for the microscope is but an eye, and
can be turned in almost any direction for purposes of in-
vestigation— it is necessary to become acquainted with the
many objects which are liable to complicate the examina-
tion of particular structures. Botli air and water are full
of floating bodies, and the most common of these should
first occupy the attention. In the city, particles of starch
are always floating in the air. Take a very minute portion
of wheat flour, place it in the middle of a clean glass " slide,"
drop upon it a drop of pure water, cover it with a plate
of thin glass, and examine it with a power of from one
hundred to six hundred diameters. It will be found to be
composed of minute grains or granules, the largest of which
are made up of coats or layers, like an onion, arranged
around a central spot called the hilum.

13. Make another preparation in the same manner, and,
after adding the water and before covering with the thin
glass cover, add a small drop of a solution of iodine.
Now, upon examining the specimen, every grain will be
seen to be of a beautiful deep blue color. After thus
studying wheat starch, the starch of Indian corn, of arrow-
root, and of various grains should be examined in like man-
ner, and their resemblances and differences noted. The
granules of potato-starch are as distinctly marked as any.
(See Fig. 15, page 61.)

14. Fibres of cotton, lint, and wool are liable to be
found in every specimen prepared for microscopical exami-
nation. In order to study these, any cotton, woollen, or
linen fabric, or garment, may be scraped, and the scrap-
ings placed on a piece of glass moistened with water, cov-
ered with the thin glass plate or cover as before, and exam-

1 2. Bodies, in air and water ? The examination of starch ?

13. The examination with solution of iodine? Advice respecting other arti-
cles ?

14. Directions for examining cotton and- other fibres ? Vegetable hairs ?

244 THE MICROSCOPE.

ined with the same magnifying power, namely, from one
hundred to six hundred diameters. Vegetable hairs or
down are constantly floating in air and water. These are
of very various forms, are simple or grouped, and form
very interesting objects of study. They are readily pro-
cured from the epidermis or outer membrane of the leaves
or stems of plants, by section with a delicate knife.

15. The tissues of plants, epidermis, ducts, and woody
fibres are constantly found in "microscopic preparations.
They may be studied in delicate sections made with
a sharp knife, or by tearing vegetable tissues apart with
needles. The down of moths, the hairs of difie rent-
animals, the fibres of paper, the most common animal-
cules in water, the dust of shelves, and generally the
structures found in all vegetable and animal substances
by which we are surrounded, should be studied as a pre-
liminary to any special line of microscopical investiga-
tion.

16. The Study of Human Tissues. — When this has
been done and familiarity with the use of the instrument
has been obtained, proceed to the study of the human
body, for human physiology is our subject. If the end of
the finger be pricked with a pin, a drop of blood may be
procured for examination. Place this on one of the glass
slides, cover it with a thin piece of glass, press down the
cover so as to make a thin layer, and then examine with
the magnifying power just mentioned. Do not add water,
for that will cause the blood corpuscles to disappear. If
the drop of blood is placed under the microscope at once
after being drawn from the finger, most interesting phe-
nomena will be observed. The red corpuscles will be seen
to arrange themselves in rows, like piles of coin, while the
blood is coagulating. The spherical, white corpuscles will

15. Directions for examining various tissues? Down of moths, and other
structures ?

1 6. Directions for examining a drop of blood ?

THE MICROSCOPE. 245

be left out of the rows of red disks, and, if the highest
power be used, will be seen to change their shape con-
stantly.

17. If you scrape with a dull knife the inside of the
cheek, the flattened scales of " pavement epithelium," or
of the insensible covering which, analogous to the scarf-
skin on the outer surface of the body, lines the cavities of
its interior, may be readily studied. They have the appear-
ance of transparent tiles, each enclosing a round or oval
body, called its nucleus. Dandruff and the scrapings
from the skin of the body are composed of scales like
those of the mouth, but they differ somewhat in being
hardened by horny matter, and in having a very faint
central body or nucleus.

18. The Tissues of the Inferior Animals. — The
warm-blooded animals do not differ in the tissues, or mi-
croscopic structures, that compose them, but only in the
amount and arrangement of these tissues. Milne Edwards
says these tissues " do not differ much in different animals,
but their mode of association varies; and it is chiefly by
reason of the differences in the combination of these asso-
ciations in various degrees, that each species possesses the
anatomical properties and characters which are peculiar
to it."

19. Hence the butcher's stall will furnish all the mate-
rials for the study of the microscopic tissues. The struc-
ture of the heart, lungs, liver, brain, and muscle may all
be studied, and well studied, by using minute pieces of
the flesh of the lower animals, especially of the quadru-
peds. Such portions of these animals as are not exposed
for sale can be readily obtained by order from the slaugh-
ter-house. To examine with the powers of which we
have been speaking, it is only necessary to cut off exceed-

1 7. Examination of the scales of the mouth ? Dandruff ?

18. In what, as respect* the tissues, do the warm blooded animals differ?
Statement of Milne Edwards ?

19. How to procure materials for the study of the tissues of man ?

246 THE MICROSCOPE.

ingly small pieces, tear them apart with needles, or make
very delicate sections with a sharp knife.

20. Incentives to Study. — A complete knowledge of
all minute structures is not to be expected at once, for you
are here introduced into a new realm of Nature, a world
of little things as vast, as wonderful, and as carefully con-
structed as the starry firmament, — that other realm of
grand objects which the astronomer nightly scans with the
telescope. It will not appear singular, therefore, if, at first,
you feel strange and awkward in this new creation. With a
little perseverance, however, and with the attention directed
toward simple objects at the outset, it will not be long be-
fore an increasing experience will engender confidence.

21. If to all this there be added an enthusiastic study of
the standard authorities on the subject, the rate of progress
will be by so much the more rapid. As compared with
similar studies, few possess more interest than microscopy,
and to the one who pursues it with fondness, it constantly
affords sources of pleasure and agreeable surprises ; and in
the end, often leads to new and valuable additions to the
sum of human knowledge. The depths which the micro-
scope is employed to fathom are no more completely known,
than are the heights above us explored and comprehended
by the astronomer.

QUESTIONS FOR TOPICAL REVIEW.
State what you can on the following subjects:

\ . Voice and speech 227, 228 ; 8. Necessity of the microscope ... 236

2. The or<;an of the voice 2-28, 229 ! 9. Convex lenses :>:J>r>, 237

3. The vocal cords 230. 231 , 10. Kinds of microscope 2:>7. 23S

4. The production of the voice. 232. 233 ; 11. Choosinsr a microscope 23'.). 242

5. The varieties of voice 233, 234 \ 12. Preliminary studies 243, 244

6. Ventriloquism 235 \ 13. The study of hnman tissues 244

7. The law of the tissues 236 I 14. The study of the inferior animals 215

APPENDIX.

POISONS AND THEIR ANTIDOTES.

ACCIDENTS from poisoning are of such frequent occurrence, thai
every one should be able to administer the more common antidotes,
until the services of a physician can be obtained. As many poisons
bear a close resemblance to articles in common use, no dangerous
substance should be brought into the household without having the
word poison plainly written or printed on the label ; and any pack-
age, box, or vial, without a label, should be at once destroyed, if the
contents are not positively known.

When a healthy person is taken severely and suddenly ill soon
after some substance has been swallowed, we may suspect that he has
been poisoned. In all cases where poison has been taken into the
stomach, it should be quickly and thoroughly evacuated by some
active emetic, which can be speedily obtained This may be accom-
plished by drinking a tumblerful of warm water, containing either a
tablespoonful of powdered mustard or of" common salt, or two tea-
spoonfuls of powdered alum in two tablespoonfuls of syrup. When
vomiting has already taken place, it should be maintained by copious
draughts of warm water or mucilaginous drinks, such as gum-water
or flaxseed tea, and tickling the throat with the finger until there is
reason to believe that all the poisonous substance has been expelled
from the stomach.

The following list embraces only the more common poisons, to
getker with such antidotes as are usually at hand, to be used until
the physician arrives.

POISONS.

Acids. — Hydrochloric acid; muriatic acid (spirits of salt); nitric
acid (aqua fortis) ; sulphuric acid (oil of vitriol).

ANTIDOTE. — An antidote should be given at once to neutralize the
acid. Strong soapsuds is an efficient remedy, and can always be
obtained. It should be followed by copious draughts of warm water
or flaxseed tea. Chalk, magnesia, soda or saleraUis (with water)' or

248 APPENDIX.

lime-water, are the best remedies. When sulphuric acid has been
taken, water should be given sparingly, because, when water unites
with this acid, intense heat is produced.
Oxalic acid.

ANTIDOTE. — Oxalic acid resembles Epsom salts in appearance, and
may easily be mistaken for it The antidotes are magnesia, or chalk
mixed with water.

Prussia Acid; oil of bitter almonds ; laurel water; cyanide of potas-
sium, (used in electrotyping).

ANTIDOTE. — Cold douche to the spine. Chlorine water, or water
of ammonia largely diluted, should be given, and the vapor arising
from them may be inhaled.

Alkalies and their Salts. — AMMONIA (hartshorn), liquor or water
of ammonia. POTASSA: — caustic potash, strong ley, carbonate of potassa
(pearlash), nitrate of potassa (saltpetre).

ANTIDOTE. — Give the vegetable acids diluted, as weak vinegar,
acetic, citric, or tartaric acids dissolved in water. Castor oil, linseed oil,
and sweet oil may also be used ; they form soaps when mixed with the
free alkalies, which they thus render harmless. The poisonous effects
of saltpetre must be counteracted by taking mucilaginous drinks
freely, so as to produce vomiting.
Alcohol.. — Brandy, wine ; all spirituous liquors.
ANTIDOTE. — Give as an emetic ground mustard or tartar emetic. If
the patient cannot swallow, introduce a stomach purnp ; pour cold
water on the head.

Gases. — Chlorine, carbonic acid gas, carbonic oxide, fumes of burning
'.haicoal, sulphuretted hydrogen, illuminating or coal-gas.

ANTIDOTE. — For poisoning by chlorine, inhale, cautiously, ammonia
(hartshorn). For the other gases, cold water should be poured upon
the head, and stimulants cautiously administered ; artificial icspira-
tion. (See Marshall Hall's Ready Method, page 250.)
Metals. — Antimony, tartar emetic, wine of antimony, etc.
ANTIDOTE. — If vomiting has not occurred, it should be produced by
tickling the throat with the finger or a feather, and the abundant use
Df warm water. Astringent infusions, such as common tea, oak bark,
and solution of tannin, act as antidotes.

Arsenic. — White arsenic, FowUr's solution, fly-powder, cobalt, Paris
green, etc.

ANTIDOTE. — Produce vomiting at once with a tablespoonful or two
of powdered mustard in a glass of warm water, or with ipecac. The
antidote is hydrated peroxide of iron. If Fowler's solution has been
taken, lime-water must be given.

APPENDIX. 249

Copper. — Acetate of copper (verdigris), sulpliate of copper (blue
vitriol), food cooked in dirty copper vessels, or pickles made green
by copper.

ANTIDOTE. — Milk or white of eggs, with mucilaginous drinks (flax
seed tea, etc.), should be freely given.

Iron.—Sulpliate of iron (copperas), etc.

AJNTIDOTE. — Carbonate of soda in some, mucilaginous drink, or in
water, is an excellent antidote.

Lead. — Acetate of lesid (sugar of lead;, carbonate of lead (white
lead), water kept in Deaden pipes or vessels, food cooked in vessels
glazed with lead.

ANTIDOTE. — Induce vomiting with ground mustard or common
salt in warm water. The antidote for soluble preparations of lead is
Epsom salts; for the insoluble forms, sulphuric acid largely diluted.

Mercury. — Bichloride of mercury (corrosive sublimate), ammoniated
mercury (white precipitate), red oxide of mercury (red precipitate), red
sulphuret of mercury (vermilion).

ANTIDOTE. — The white of eggs, or wheat flour beaten up with
water and milk, are the best antidotes.

Silver. ^— Nitrate of silver (lunar caustic).

ANTIDOTE. — Give a teaspoonful of common salt in a tumbler of
water. It decomposes the salts of silver and destroys their activity.

Zinc. — Sulphate of zinc, etc. (white vitriol).

ANTIDOTE. — The vomiting may be relieved by copious draughts
of warm water. The antidote is carbonate of soda administered in
water.

Narcotic Poisons. — Opium (laudanum, paregoric, salts of mor-
phia, Godfrey's cordial, Dalby's carminative, soothing syrup, cholera
mixtures), aconite, belladonna, hemlock, stramonium, digitalis, tobacco,
hyosciamus, nux wmica, strychnine.

ANTIDOTE. — Evacuate the stomach by the most active emetics, as
mustard, alum, or sulphate of zinc. The patient should be kept in
motion, and cold water dashed on the head and shoulders. Strong
coffee must be given. The physician will use the stomach pump and
electricity. In poisoning by nux vomica or strychnine, etc., chloro-
form or ether should be inhaled to quiet the spasms.

Irritant Vegetable Poisons. — Croton oil, oil of samne, poke, oil of
tansy, etc.

ANTIDOTE — If vomiting has taken place, it may be rendered easier
by copious draughts of warm water. But if symptoms of insensibility
have come on without vomiting, it ought to be immediately excited b>
ground mustard mixed with warm water, or some other active emo!;r

11*

250 APPENDIX.

and after its operation an active purgative should be given. Aftei
evacuating as much of the poison as possible, strong coffee or vinegar
and water may be given with advantage.

Poisonous Fish. — Conger eel, musseU, crabs, etc.

ANTIDOTE.— Evacuate, as soon as possible, the contents of the stom-
ach and bowels by emetics (ground mustard mixed with warm water
or powdered alum), and castor oil, drinking freely at the same time
of vinegar and water. Ether, with a few drops of laudanum mixed
with sugar and water, may afterward be taken freely.

Poisonous Serpents. — ANTIDOTE. — A ligature or handkerchief
should be applied moderately tight above the bite, and a cupping-glass
over the wound. The patient should drink freely of alcoholic stim-
ulants containing a small quantity of ammonia. The physician may
inject ammonia into the veins.

Poisonous Insects. — Stings of scorpion, hornet, wasp, bee, etc.

ANTIDOTE. — A piece of rag moistened with a solution of carbolic
acid may be kept on the affected part until the pain is relieved ; and
a few drops of carbolic acid may be given frequently in a little
water. The sting may be removed by making strong pressure
around it with the barrel of a small watch-key.

DROWNING.

MARSHALL HALL'S " READY METHOD" of treatment in asphyxia
from drowning, chloroform, coal gas, etc.

1st. Treat the patient instantly on the spot, in the open air, freely
exposing the face, neck, and chest to the breeze, except in severe
weather.

2d. In order to clear ike throat, place the patient gently on the face,
with one wrist under the forehead, that all fluid, and the tongue itself,
may fall forward, and leave the entrance into the windpipe free.

3d. To excite respiration, turn the patient slightly on his side, and
apply some irritating or stimulating agent to the nostrils, as vera
trine^ dilute ammonia, etc.

4th. Make the face warm by brisk friction ; then dash cold water
upon it.

5th. If not successful, lose no time ; but, to imitate respiration,
place the patient on his face, and turn the body gently, but completely
on iJieside, and a little beyond; then again on the face, and so on, al-
ternately. Repeat these movements, deliberately and perseveringly.

APPENDIX. 25]

•fifteen times only in a minute. (When the patient lies on the thorax,
this cavity is compressed by the weight of the body, and ezpiratiOD
takes place. When he is turned on the side, this pressure is removed,
and t/ispiration occurs.)

6th. When the prone position is resumed, make a uniform and
efficient pressure along the spine, removing the pressure immediately,
before rotation on the side. (The pressure augments the expiration •
the rotation commences z'ftspiration.) Continue these measures.

7th. Rub the limbs upward, with firm pressure and with energy.
(The object being to aid the return of venous blood to the heart.)

8th. Substitute for 'the patient's wet clothing, if possible, such
other covering as can be instantly procured, each bystander sup-
plying a coat or cloak, etc. Meantime, and from time to time, to
excite inspiration, let the surface of the body be slapped briskly with
the hand.

9th. Rub the body briskly till it is dry and warm, then dash fold
water upon it, and repeat the rubbing.

Avoid the immediate removal of the patient, as it involves a
dangerous loss of time — also, the use of bellows, or any forcing instru-
ment ; also, the warm bath, and all rough treatment.

GLOSSARY.

AB-DO'MEN (Latin abdo, to conceal). The largest cavity of the bouy
containing the liver, stomach, intestines, etc.; the belly.

AB-SOR'BENTS (L. db and sorbeo, to suck up). The vessels which take
part in the process of absorption.

AB-SORP'TION. The process of sucking up fluids by means of an
animal membrane.

AC-COM-MO-DA'TION of the Eye. The alteration in the shape of the
crystalline lens, which accommodates or adjusts the eye for near
and remote vision.

AC'ID, LACTIC (L. lac, milk). The acid ingredient of sour milk ; the
gastric juice also contains it.

AL-BU'MEN, or Albumin (L. albus, white). An animal substance re-
sembling white of egg.

AL-BU'MI-NOSE (from albumen). A soluble animal substance pro-
duced in the stomach by the digestion of the albuminoid sub-
stances.

AL-BU'MIX-OID substances. A class of proximate principles resembling
albumen ; they may be derived from either the animal or vegetable
kingdoms.

AL'I-MENT (L. alo, to nourish). That which affords nourishment ;
food.

AL-I-MENT'A-BY CA-NAL (from aliment). A long tube in which the
food is digested, or prepared for reception into the system.

AN-^ES-THET'ICS (Greek, ar, an, without, cdtiSijtita, aistliesia, feel
ing). — Those medicinal agents which prevent the feeling of pain,
such as chloroform, laughing-gas, etc.

AN-I-MAI/CULE (L. animal'culum, a small animal). Applied to an-
imals which can only be seen with the aid of the microscope. Ani-
malculum (plural, animalcula) is used with the same meaning.

A-OR'TA (Gr. dopreotiai, aorteomai, to be lifted up). The largest
artery of the body, and main trunk of all the arteries. It arises from
the left ventricle of the heart. The name was first applied to the
two large branches of the trachea, which appear to be lifted up by
the heart.

GLOSSARY.

A'QUE-OUS HUMOR (L. aqua, water). A few drops of watery color-
less fluid occupying the space between the cornea and crystalline
lens.

A-RACH'NOID MEM'BRANE (Gr. ctpaxTT/, arachne, a cobweb, and
siSoS, eidos, like). An extremely thin covering of the brain and
spinal cord. It lies between the dura mater and the pia mater.

A.R'BOR VI'T^E (L.). Literally, "the tree of life;" a name given to the
peculiar appearance presented by a section of the cerebellum.

AR'TER-Y (Gr. cirip, aer, air, and Tijpsiv, terein, to contain). A
vessel by which blood is conveyed away from the heart. It was
supposed by the ancients to contain air ; hence the name.

AR-TIC-U-LA'TION (L. articulo, to form a joint). The more or less
movable union of bones, etc. ; a joint.

A-RYT'E-NOID CAR'TI-LA-GES (Gr. apvroara, arutaina, a pitcher).
Two small cartilages of the larynx, resembling the mouth of a
pitcher.

A S-SIM-I-LA'TION (L. ad, to, and similis, like). The conversion of food
into living tissue.

AU-DI'TION (L. audio, to hear). The act of hearing sounds.

AU'DI-TO-RY NERVE. One of the cranial nerves; it is the special
nerve of hearing.

AU'RI-CLE (L. auris, the ear). A cavity of the heart.

BAR'I-TONE (Gr. fiapvt, barus, heavy, and roVo?, tonos, tone). A
variety of male voice between the bass and tenor.

BEL-LA-DON'NA (It. beautiful lady). A vegetable narcotic poison. It
has the property of enlarging the pupil, and thus increasing the
brilliancy of the eye ; so called from its use by Italian ladies.

BI-CUS'PID (L. U, two, and cuspis, prominence). The name of the
fourth and fifth teeth on each side of the jaw ; possessing two prom-
inences.

BILE. The gall, or peculiar secretion of the liver ; a viscid, yellowish
fluid, and very bitter to the taste.

BRONCH'I (Gr. fipoyxoS, bronkos, the windpipe). The two first
divisions or branches of the trachea ; one enters each lung.

BRONCH'I- AL TUBES. The smaller branches of the trachea within
the substance of the lungs, terminating in the air-cells.

BRONCH-I'TIS (from bronchia, and itis, a suffix signifying inflamma-
tion). An inflammation of the larger bronchial tubes ; a " cold"
affecting the lungs.

CAL-CA'RE-OUS (L. calx, lime). Containing lime.

CA-NAL' (L.). In the body, any tube or passage.

CA-NINE' (L. canis, a dog). Name given to the third tooth on each

254 GLOSSARY.

side of the jaw ; in the upper jaw it is also known as the eye-tootn:
pointed like the tusks of a dog.

CAP'IL-LA-RY (L. capil'lus, a hair, capiUa'rix hair-like). The name of
the extremely minute blood-vessels which connect the arteries with
the veins.

CAR'BON DIOX-IDE (CO»). Chemical name for carbonic acid gas.

CAR-BON' ic A-CID. The gas which is present in the air expired from
the lungs ; a waste product of the animal kingdom, and a food of
the vegetable kingdom.

CAR'DI-AC (Gr. xapdia, cardia, the heart). The cardiac orifice of
the stomach is the upper one, and is near the heart ; hence its
name.

CAR-NIV'O-ROUS (L. ca'ro, flesh, and w'ro, to devour). Subsisting
upon flesh.

CA-ROT'ID AR-TE-RT. The large artery of the neck, supplying the
head and brain.

CAR'TI-LAGE. A solid but flexible material, forming a part of the
joints, air-passages, nostrils, etc. ; gristle.

CA'SE-INE (L. ca'seus, cheese). The albuminoid substance of milk ;
it forms the basis of cheese.

CER-E-BEL'LUM (diminutive for cer'ebrum, the brain). The little brain,
situated beneath the posterior third of the cerebrum.

CER'E-BRUM (L.). The brain proper, occupying the entire upper por-
tion of the skull. It is nearly divided into two equal parts, called
" hemispheres," by a cleft extending from before backward.

CHO'ROID (Gr. xopiov, chorion, a membrane or covering). The mid-
dle tunic or coat of the eyeball.

CHYLE (Gr. *vA.o'£, cliulos, juice). The milk-like fluid formed by the
digestion of fatty articles of food in the intestines.

CHYME (Gr. j^v/noS, ckumos, juice). The pulpy liquid formed by
digestion within the stomach.

CIL'I-A (pi. of til'i-um, an eyelash). Minute, vibratile, hair -like pro-
cesses found upon the cells of the air-passages, and other parts that
are habitually moist.

CIR-CU-LA'TION (L. cir'culus, a ring). The circuit, or course of the
blood through the blood-vessels of the body, from the heart to the
arteries, through the capillaries into the veins, and from the veins
back to the heart.

CO-AQ-U-LA'TION (L. coatfulo, to curdle). Applied to the process by
which the blood clots or solidifies.

COCH'LE-A (L. coch'lea, a snail-shellV The spiral cavity of the in-
ternal ear.

GLOSSARY. 255

CONCH' A (Gr. noyxrj, konche, a mussel-shell). The external shell-
sliap jd portion of the external ear.

OON-JTTNC-TI'VA (L. con and jurigo, to join together). A thin layer
of mucous membrane which lines the eyelids and covers the front
of the eyeball ; thus joining the latter to the lids.

OON-TRAC-TIL'I-TY (L. con and tra'ho, to draw together). The prop-
erty of a muscle which enables it to contract, or draw its extrem-
ities closer together.

OON-VO-VQ'TIONS (L. con and vol'vo, to roll together). The tortuous
foldings of the extenal surface of the brain.

CON-VUJ/SION (L. convel'lo, to pull together). A more or less violent
agitation of the limbs or body.

COR'NE-A (L. cor'nu, a horn). The transparent, horn-like substance
which covers the anterior fifth of the eyeball.

COR'FUS-CLES, BLOOD (L. dim. of cor' pus, a body). The small bicon-
cave disks which give to the blood its red color ; the white cor-
puscles are globular and larger.

COS-MET'IC (Gr. nodjusoa, kosmeo, to adorn). Beautifying; applied
to articles which are supposed to increase the beauty of the
skin, etc.

CRA'NI-AL (L. cra'nium, the skull). Pertaining to the skull. The
nerves which arise from the brain are called cranial nerves.

CKI'COID (Gr. KpixoS, kri'kos, a ring). A cartilage of the larynx,
resembling a seal-ring in shape.

CRYS'TAL-LINE LENS (L. crystal'lum, a crystal). One of the so-called
humors of the eye ; a double convex body situated in the front part
of the eyeball.

CU'TI-CLE (L. dim. ofcu'tis, the skin). The scarf-skin ; also called
the epider'mis.

CU'TIS (Gr. <5nvro$% skutos, a skin or hide). The true skin, lying
beneath the cuticle ; also called the der'ma.

DE-CUS-SA'TION (L. decus'sis, the Roman numeral ten, X). A re-
ciprocal crossing of fibres from side to side.

DI'A-PHRAGM (Gr. dtacppdddoo, diaplirasso, to divide by a partition).
A large, thin muscle which separates the cavity of the chest from
the abdomen ; a muscle of respiration.

DIF-FUS'ION OF GASES. The power of gases to become intimately
mingled, without reference to the force of gravity.

DUCT (L. du'co, to lead). A narrow tube ; the flwracic duct is the
main trunk of the absorbent vessels.

DU-O-DE'NUM (L. duode'ni, twelve). The first division of the small
intestines, about twelve fingers-breadth long.

256 GLOSSARY.

DU'RA MA'TER (L.). Literally, the hard mother ; the tough membrane
which envelops the brain.

UYS-PEP'SI-A (Gr. dvS, dus, difficult, an&iteitrGOypep'to, to digest). Dif-
ficult or painful digestion ; a disordered condition of the stomach.

E-MUI/SION (L. emul'geo, to milk). Oil in a finely divided state sus-
pended in water.

EN-AM'EL (Fr. email). The dense material which covers the crown
of the tooth.

EN'ER-GY, Specific, of a Nerve. When a nerve of special sense is
excited, whatever be the cause, the sensation experienced is that
peculiar to the nerve ; this is said to be the law of the specific
energy of the nerves.

EP-I-GLOT'TIS (Gr. £7ti, epi, upon, and yXoorriS, glottis, the entrance
to the windpipe). A leaf-shaped piece of cartilage which covers
the top of the larynx during the act of swallowing.

EX-CRE'TION (L. excer'no, to separate). The separation from the blood
of the waste particles of the body ; also the materials excreted.

EX-PI-RA'TION (L. expi'ro, to breathe out). The act of forcing air out
of the lungs.

EX-TEN'SION (L. ex, out, and ten' do, to stretch). The act of restoring a
limb, etc., to its natural position after it has been flexed, or bent ;
the opposite of Flexion.

FE-NES'TRA (L.). Literally, a window ; the opening between the
middle and internal ear.

FI'BRIN (L. fi'bra, a fibre). An albuminoid substance found in the
blood; in coagulating it assumes a fibrous form.

FLEX' ION (L. flee' to, to bend). The act of bending a limb, etc.

FOL/LI-CLE (L. dim. offol'lis, a bag). A little pouch or depression in a
membrane ; it has generally a secretory function.

FUN'GOUS GROWTHS (L.fun'gus, a mushroom). A low grade of vege-
table life.

GAN'GLI-ON (Gr. yayyXiov, ganglion, a knot). A knot-like swell-
ing in the course of a nerve ; a smaller nerve-centre.

GAS'TRIC (Gr. yadrrfp, gaster, stomach). Pertaining to the stomach.

GLAND (L. glans, an acorn). An organ consisting of follicles and
ducts, with numerous blood-vessels interwoven ; it separates some
particular fluid from the blood.

TLOS'SO-PHAR-YN-GE'AL NERVE (Gr. yXooGGa, glossa, the tongue, and
(pdpvyE, pharunx, the throat). The nerve of taste supplying the
posterior third of the tongue; it also supplies the throat

GLU'TEN (L.). Literally, glue : the glutinous albuminoid ingredient
of wheat.

GLOSSARY. 257

E (L. dim. of gra'num, a grain). A little grain; a micro-
scopic object.

GUS-TA'TION (L. gus'to, to taste). The sense of taste.
GUS'TA-TO-RY NERVE. The nerve of taste supplying the front part

of the tongue; a branch of the " fifth" pair.
ELEM'OR-RHAGE (Gr. ai/j.a, hai'ma, blood, and pijyrvjui, regnumi,

to burst). Bleeding, or the loss of blood.
HEM-I-PLE'GIA (Gr. ^//ztfuS, hemisus, half, and TrA^tftfoj, pletso, to

strike). Paralysis, or loss of power, affecting one side of the body.
HEM'I-SPHERES (Gr. ticpoupa, sphaira, a sphere). Halt a sphere, the
- lateral halves of the cerebrum, or brain proper.
HE-PAT' ic (Gr. r/ttap, tiepar, the liver). Pertaining to the liver.
HER-BIV'O-ROUS (L. lier'ba, an herb, and vo'ro to devour). Applied

to animals that subsist upon vegetable food.
HU'MOR (L.). Moisture : the humors are transparent contents of the

eyeball.
HY-DRO-PHO'BI-A (Gr. vdop, hudor, water, and fpofiea), phobeo, to

fear). A disease caused by the bite of a rabid dog or other animal.

In a person affected with it, convulsions are occasioned by the sight

of a glittering object, like water, by the sound of running water,

and by almost any external impression.
HY'GI-ENE (Gr. vyi£ia, huygieia, health). The art of preserving

health and preventing disease.
HY'PER-O-PI-A. Abbreviated from HY'PER-MET-RO'PI-A (Gr. vnep,

kupei\ beyond, juerpov, metron, the measure, and ooip, ops, the eye).

A defect of vision dependent upon a too short eyeball ; so called

because the rays of light are brought to a focus at a point behind

the retina ; the true " far sight."
IN-CI'SOR (L. ind'do, to cut). Applied to the four front teeth of both

jaws, which have sharp cutting edges.
IN'CTJS (L). An anvil ; the name of one of the bones of the middle

ear.
IN-SAL-I-VA'TION (L. in, and salfva, the fluid of the mouth). The

mingling of the saliva with the food during the act of chewing.
IN-SPI-RA'TION (L. t», and spi'ro, spira'tum, to breathe). The act of

drawing in the breath.
IN-TEG'U-MENT (L. t», and te'go, to cover). The skin, or outer covering

of the body.
IN-TES'TTNE (L. in'tus, within). The part of the alimentary canal

which is continuous with the lower end of the stomach ; also called

the intestines, or the bowels.
['RIS (L. i'ris, the rainbow). The thin muscular ring which lies be-

258 GLOSSARY.

tween the cornea and crystalline lens, and which gives the eye

its brown, blue, or other color.
JU'GU-LAR (L.ju'gulum, the throat). The name of the large veins

which run along the front of the neck.
LAB'Y-RESTH (Gr. A.afivpir$o$, labunn'thos, a building with many

winding passages). The very tortuous cavity of the inner ear,

comprising the vestibule, semicircular canals, and the cochlea.
LACH'RY-MAL APPARATUS (L. lach'ryma, a tear). The organs for

forming and conveying away the tears.
LAC'TE-ALS (L. lac, lac'tis, milk). The absorbent vessels of the small

intestines ; during digestion they are filled with chyle, which has

a milky appearance.
LA-RYN'GO-SCOPE (Gr. Hdpvy$9 larunx, the larynx, and tino-tea),

skopeo, to look at). The instrument by which the larynx may be

examined in the living subject.
LAR'YNX (Gr.). The cartilaginous tube situated at the top of the

windpipe, or trachea ; the organ of the voice.

LENS (L.). Literally, a lentil ; a piece of transparent glass or other sub-
stance so shaped as either to converge or disperse the rays of light.
I jo A-MENT (L. I? go, to bind). A strong, fibrous material binding

bones or other solid parts together ; it is especially necessary to

give strength to joints.
LIG'A-TURE. A thread of silk or other material used in tying around

an artery.

LYMPH (L. lym'pha, spring-water). The colorless, watery fluid con-
veyed by the lymphatic vessels.

LYM-PHAT'IC VESSELS. A system of absorbent vessels.
MAL'LE-US (L.). Literally, the mallet; one of the small bones of the

middle ear.
MAR'ROW. The soft, fatty substance contained in the central cavities

of the bones : the spinal marrow, however, is composed of nervous

tissue.

MAS-TI-CA'TTON (L. mas'tico, to chew). The act of cutting and grind-
ing the food to pieces by means of the teeth.
ME-DUL'LA OB-LON-GA'TA. The " oblong marrow," or nervous cord.

which is continuous with the spinal cord within the skull.
MEM-BRA'NA TYM'PAN-I (L.). Literally, the membrane of the drum ;

a delicale partition separating the outer from the middle ear; it is

sometimes incorrectly called the drum of the ear.
MEM'BRANE. A thin layer of tissue serving to cover some part of

the body.
MI'CRO-SCOPE (Gr. yutx/oo?, mflf.rn*) small, and ^H^TTSGOJ skopeo^ to

GLOSSARY. 259

look at). An optical instrument which assists in the examination

of minute objects.
MO'LAR (L. mo'la, a mill). The name applied to the three back teeth

of each side of the jaw ; the grinders, or mill-like teeth.
MO'TOR (L. mo'veo, mo' turn, to move). Causing motion ; the name

of those nerves which conduct to the muscles the stimulus which

causes them to contract.

Mu'cous MEM'BRANE. The thin layer of tissue which covers those in-
ternal cavities or passages which communicate with the external air.
Mo'cus. The glairy fluid which is secreted by mucous membranes,

and which serves to keep them in a moist condition.
MY-O'PI-A (Gr. m'ao, muo, to contract, and GOI{>, ops, the eye). A de-
fect of vision dependent upon an eyeball that is too long, rendering

distant objects indistinct ; near-sight.
NA'SAL (L. na'sus, the nose). Pertaining to the nose ; the n(tsa>

cavities contain the distribution of the special nerve of smeil.
NERVE (Gr. vevpor, neuron, a cord or string). A glistening, white

cord of cylindrical shape, connecting the brain or spinal cord with

some other organ of the body.
NERVE CELL. A minute, round and ashen-gray eel1 umnd in the

brain and other nervous centres.
NERVE FI'BRE. An exceedingly slender thread of nervous tissue

found in the various nervous organs, but especially in the nerves ;

it is of a white color.
NU-TRI'TION (L. nu'trio, to nourish). The processes by which the

nourishment of the body is accomplished.
(E-SOPH'A-GUS (Gr.). Literally, that which carries food. The tube

leading from the throat to the stomach ; the gullet.
O-LE-AG'I-NOUS (L. o'leum, oil). Of the nature of oil : applied to aii

important group of food-principles — the fats.

OL-FAC'TO-RY (L. olfa'cio, to smell). Pertaining to the sense of smell.
OPH-THAL'MO-SCOPE (Gr. o<p3o:/l//o?, ophthalmos, the eye, and GKO~

item, skopeo, to look at). An instrument devised for examining the

interior of the globe of the eye.

OP'TIC (Gr. oTtTGOj opto, to see). Pertaining to the sense of sight.
OR'BIT (L. or'bis, the socket). The bony socket or cavity in which

the eyeball is situated.
OS'MOSE (Gr. aodjuoS, osmos, a thrusting or impulsion). The process

by which liquids are impelled through a moist membrane.
OS'SE-OUS (L. os, a bone). Consisting of, or resembling bone.
PAL' ATE (L. pala'tum, the palate). The roof of the mouth, consisting

of the hard and soft palate.

260 GLOSSARY.

PAL'MAR. Relating to the palm of the hand.

PAN'ORE-AS (Gr. Ttat, Karros, pas, pantos, all, and xpsaS, kreas,
flesh). A long, flat gland situated near the stomach ; in the lower
animals the analogous organ is called the sweet-bread.

PA-PIL'L^E (L. papil'la). The minute prominences in which termi-
nate the ultimate fibres of the nerves of touch and taste.

PA-RAi/r-srs. A disease of the nervous system marked by the !;/»s
of sensation, or voluntary motion, or both ; palsy.

PAR-A-PI.E'GI-A (Gr. Ttapa.7fXrf(5(5Ga, paraplesso, to strike amiss). A
form of paralysis affecting the lower half of the body.

PA-TEL' LA (L. dim. of pat'ina, a pan). The knee-pan; a small
bone.

PEL'VIS (L.). Literally a basin ; the bony cavity at the lower part of
the trunk.

PEP'SIN (Gr. TteifcGo, pepto, to digest). The organic principle of the
gastric juice.

PER-I-STAL'TIC MOVE'MENTS (Gr. XEpttfrsAXco, peristello, to contract).
The slow, wave-like movements of the stomach and intestines.

PER-I-TO-NE'UM (Gr. TtspireivGo, penteino, to stretch around). The
investing membrane of the stomach, intestines, and other abdom-
inal organs.

PER-SPI-RA'TTON (L. persptro, to breathe through). The sweat, or
watery exhalation of the skin ; when visible, it is called sensible
perspiration, when invisible, it is called insensible perspiration.

PE'TROUS (Gr. xsrpa, petra, a rock). The name of the hard portion
of the temporal bone, in which is situated the drum of the ear and
labyrinth.

PHAR'YNX (Gr. cpdpvyk, pJiarunx, the throat). The cavity between
the back of the mouth and gullet.

PHYS-I-OL'CMSY (Gr. <pv<5i$, phusis, nature, and Ad^o?, logos, a dis-
course). The science of the functions of living, organized beings.

PI'A MA'TER (L.). Literally, the tender mother; the innermost of the
three coverings of the brain. It is thin and delicate ; hence the
name.

PLEU'RA (Gr. nXEvpa, a rib). A membrane covering the lung and
lining the chest. There is one for each lung.

PLEU'RI-SY. An inflammation affecting the pleura.

PNEU-MO-GAS'TRIC (Gr. TCVEVJJ.&V, pneumon, the lungs, and ya6Ti)pt
gaster, the stomach). The name of a nerve distributed to the lungs
and stomach ; it is the principal nerve of respiration.

PNEU-MO'NIA (Gr.). An inflammation affecting the air-cells of the
lungs.

GLOSSARY. 261

PRES-BY-O'PI-A (Gr. TtpsdfiVs, presbuS) old, and GJI/>, ops, the eye).
A defect of the accommodation of the eye, caused by the harden-
ing of the crystalline lens ; the " far-sight" of adults and aged
persons.

PJIOC'ESS (L. proce'do, proces'sus, to proceed, to go forth). Any pro-
jection from a surface. Also, a method of performance ; a pro-
cedure.

PTY'A-LIN (Gr. itrvaXov, ptualon, saliva). The peculiar organic
ingredient of the saliva.

PUL'MO-NA-RY (L. pul'mo, pulmo'nis, the lungs). Pertaining to the
lungs.

PULSE (L. pel'lo, pul'sum, to beat). The striking of an artery against
the finger, occasioned by the contraction of the heart, commonly
felt at the, wrist.

PU'PIL (L. pupil'la). The central, round opening in the iris, through
which light passes into the depths of the eye.

PY-T>O'RUS (Gr. 7tvha)p6's, puloros, a gate-keeper). The lower open-
ing of the stomach, at the beginning of the small intestine.

RE'FLEX ACTION. An involuntary action of the nervous system, by
which an external impression conducted by a sensory nerve is
reflected, or converted into a motor impulse.

RES-FI-RA'TION (L. res'piro, to breathe frequently). The function
of breathing, comprising two acts : inspiration, or breathing in, and
expiration, or breathing out.

HET'I-NA (L. re'te, a net). The innermost, of the three tunics or coats
of the eyeball, being an expansion of the optic nerve.

SAC'CHA-RINE (L. sac'cliarum, sugar). Of the nature of sugar;
applied to the important group of food substances which embraces
the different varieties of sugar, starch, and gum.

SA-LI'VA (L.). The moisture or fluids of the mouth, secreted by the
salivary glands, etc.

SCLE-ROT'IC (Gr. tiKXrjpoS, skleros, hard). The tough, fibrous outer
tunic of the eyeball.

SE-BA'CEOUS (L. sebum, fat). Resembling fat , the name of tnc oily
secretion by which the skin is kept flexible and soft.

SE-CRE'TION (L. secer'no, secre'tum, to separate). The process ol
separating from the blood some essential important fluid ; which
fluid is also called a secretion.

SEM-I-CIR'CU-LAR CANALS. A portion of the internal ear.

SEN-SA'TION. The perception of an external impression by the ner-
vous system ; a function of the brain.

SEN-SI-BIL'I-TY, GENERAL. The power possessed by nearly aU parts

262 GLOSSARY.

of the human body of recognizing the presence of foreign objects
that come in contact with them.

SE'RUM (L.). The watery constituent of the blood, which separates
from the clot during the process of coagulation.

SKEL'E-TON (Gr.). The bony framework of an animal, the different
parts of which are maintained in their proper relative positions.

SPEC'TRO-SCOPE (from spec'trum and tino-neco, scopeo, to examine the
spectrum). An instrument employed in the examination of the
spectrum of the sun or any other luminous body.

SPHYG'MO-GRAPH (Gr. GcpvynoS, sphugmos, the pulse, and ypaqxa,
grapl*), to write). An ingenious instrument by means of which
the pulse is delineated upon paper.

STA'PES (L.). Literally, a stirrup ; one of the small bones of the tym-
panum, or middle ear, resembling somewhat a stirrup hi shape.

SYM-PA-THET'IC SYSTEM OF NERVES. A double chain of nervous
ganglia, connected together by numerous small nerves, situated
chiefly in front of and on each side of the spinal column.

SYN-O'VI-A (Gr. dvv, sun, and coov, oon, resembling an egg). The
lubricating fluid of joints, so called because it resembles the white
of egg.

SYS'TO-LE (Gr. 6v tfrs'AAo?, sustello, to contract). The contraction of
the heart, by which the blood is expelled from that organ.

TAC'TILE (L. tac'tus, touch). Relating to the sense of touch.

TEM'PO-RAL (L. tem'pust time, and tem'pora, the temples). Pertain-
ing to the temples ; the name of an artery : so called, because the
hail begins to turn white with age in that portion of the scalp.

TEN'DON (L. ten'do, to stretch). The white, fibrous cord or band by
which a muscle is attached to a bone ; a sinew.

TET'A-NUS (Gr. retroo, teino, to stretch). A disease marked by per-
sistent contractions of all or some of the voluntary muscles ;
those of the jaw are sometimes solely affecte^ the disorder is then
termed locked-jaw.

THO'RAX (Gr. Scopac, thorax, a breastplate). The upper cavity of
the trunk of the body, containing the lungs, heart, etc. ; the
chest.

THY'ROID (Gr. 3vp£o'S, thureos, a shield). The largest of the carti-
lages of the larynx ; its angular projection in the front of the neck
is called " Adam's apple."

TRA'CIIE-A (Gr. rpaxvS, trachus, rough). The windpipe, or the
largest of the air-passages ; composed in part of cartilaginous
rings, which render its surface rough and uneven.

TKANS-FU'SION (L. tramfun'do. to pour from one vessel to another).

GLOSSARY. 203

The operation of injecting blood taken from one person into the
veins of another; other fluids than blood are sometimes used.

TJUCII-I'NA SPI-RA'LIS. (L.) A minute species of parasite or worm,
which infests the flesh of the hog, and which may be introduced
into the human system by eating pork not thoroughly cooked.

TYM'PA-NUM (Gr. TV/J.TCO.VOV, tumpanon, a drum). The cavity of
the middle ear, resembling a drum in being closed by two mem-
branes, and in having communication with the atmosphere.

U'vu-LA (L. uva, a grape). The small pendulous body attached to
the back part of the palate.

VAS'CU-LAR (L. vas'culum, a little vessel). Pertaining to, or contain-
ing blood-vessels.

VE'NOUS (L. v^na, a vein). Pertaining to, or contained within a
vein.

VEN-TI-LA'TION. The introduction of fresh air into a room or build-
ing, in such a manner as to keep the air within it in a pure condi-
tion.

VEN-TRIL'O-QUISM (L. ven'ter, the belly, and lo'quw, to speak). A
modification of natural speech by which the voice is made to
appear to come from a distance. The ancients supposed that the
voice was formed in the belly ; hence the name.

VEN'TRI-CLES of the heart. The two largest cavities of the heart,
situated at its apex or point.

VER'TE-BRAL COLUMN (L. ver'tebra, a joint). The back-bone, con-
sisting of twenty-four separate bones, called vertebrae, firmly jointed
together ; also called the spinal column and spine.

VES'TI-BULE. A portion of the internal ear, communicating with the
semicircular canals and the cochlea ; so called from its fancied
resemblance to the vestibule or porch of a house.

VIL'LI (L. vil'lus, the nap of cloth). Minute thread-like projections
found upon the internal surface of the small intestine, giving it a
velvety appearance.

VIT'RE-OUS (L. >oi'trum, glass). Having the appearance of glass ;
applied to the humor occupying the largest part of the cavity of
the eyeball.

VIV-I-SEC'TION (L. vi'vvj, alive, and se'co, to cut). The practice of
operating upon living animals, for the purpose of studying some
physiological process.

VOCAL CORDS. Two elastic bands or ridges situated in the larynx :
they are the essential parts of the organs of tie voice.

INDEX

A.

PAGE

. 97
96

Absorbent vessels

Absorption

by blood-vessels

by the lacteals 96

of the food 96

Accommodation, function of 213

Achilles, tendon of. 27

Adam's apple 229

Air, atmospheric 131

Changes in, in respiration 132

Carbonic acid in 1:38

Composition of 131

Dust in the 137

Effects of impure 13!)

Impurities in 136

Matters in the expired 13->

Provision for purifying. 141

Renovation by ventilation 142

Air-cells of the lungs 125

Air-passages 125

Albinos 44

Albumen 58

of the blood 102

Albuminoid substaiun- 57

Varieties of 57

Properties of. . . 57-58

Albuminose. ... 94

Alcoholic liquors 77

Physiological action of 78

Alinientary canal. 81

Animal functions 148

Animal heat 143

how produced 143

regulated by perspiration 145

Animals, relative strength of 28

Apoplexy .% . . 171

Aqueous humor .' . . 210

Arachnoid membrane 152

Arbor vitse 154

Arterial blood ... 107-135

differs from venous 135

Arteries 114

Arrangement of 115

Carotid 116

Distribution of 115

Pulsation of. 115

Radial 116

Temporal 116

Arytenoid cartilage 229

Asphyxia 250

Assimilation 80, 121

Audition 215

12

^

Auditory canal 218

nerve 222

Auricles of the heart 109

B.

Back-bone 21

Bathing 47

Importance of. 47

Time and manner of .49

Baths 48

Different kinds of 48

Belladonna 206

dilates the pupil 206

Use as a cosmetic 206

Bile 95

Secretion of, in the liver 95

Accumulation of, in the gall-bladder 95

Uses of 95

Biliary duct . 95

Bladder, Gall- 95

Bleeding, how stopped 121

Blind-spot 207

Blood 101

Arterial 107-135

Change of color 107

Circulation of. 107, 133

Coagulation of 105

Composition of 102

corpuscles 102, 103

fluid 105

Microscopic appearance of 102

Respiratory changes in 133

Uses of the 105

Venous 107, 135

Blood-vessels 114, 118

Absorption by 96

Injuries to the 121

Body, renovation of the (Hi

Bones 15

Form and composition of 16

Growth of. 22

Microscopic structure of 17

Repair of. 23

Structure of 17

Uses of 15

Bowels 94

Brain 150

Anatomical structure of 152

Function of the 172

Injuries of the 173

Membranes of the 152

Reflex action of the 174

266

INDEX.

PAGE

Bread 72

Bronchial tubes 125

Bronchitis 128

C.

Canals, Semicircular ..223

Capillary blood-vessels .' 118

Circulation in the 118

Carbonic acid . 132

exhaled from the lungs 132

in the air 138

retention in tiie blood 134

Cartilage 20

Arytenoid 229

Cricoid . . 229

Thyroid 229

Casein 58

Cataract 210

Cells, Nerve ... 150, 159

Ciliated 128

Cerebellum 153

Function of the 172

Cerebro-spinal nervous system 150

Cerebrum .^ 152

Function of tie 172

Cheese 58

Chest, Framework of. 19

Contents of 'th.e 19

Chocolate : '. . . 77

Chorea 169

Choroid coat of the ?ye 204

Chyle 95

Chyme 94

Cilia 128

Circulation 107

ill the frog's foot 119

of the blood 107

Kapidity of 120

through the heart 112

Through the lungs 123

Clothing 51

Coagulation of milk 58

of the blood 104

Cochlea 223

Coflee 75

Effects of 75, 76

Collar-bone 19

Color-blindness 209

Column, Spinal 21

Combustion, Spontaneous 145

Complexion 44

Concha of the ear 217

Conjunctiva 200

Contraction of heart Ill

of muscles 27

Convulsions 169

Cooking 70

Cords, Vocal 126, 230

Cornea 203

Corpuscles, Blood 102

Cosmetics 51

Cranial ganglia 150

Functions of 171

Cranial nerves 154

Cranium 19

Cricoid cartilage 229

Crystalline lens 209

Uses of.., .. 210

PAGE

Cuticle 41

Function of 183

Cutis • 42

D.

Decussation of motor and sensory

fibres of spinal cord 164

Dentition of infancy 82

Diaphragm. Movements of the, in

respiration 128, 129

Diastole of the heart Ill

Diet, Mixed 66, 85

Necessity for changing 67

Necessity of a regulated 62

The best 63

Digestion. 80

Circumstances affecting 97

Gastric 93

Intestinal 94

Nature of 81

Organs of 81-91

Drownintr 250

Duct, Biliary 95

Nasal 201

Pancreatic 95

Thoracic ' 97

Dura Mater. . . . . 152

B.

Ear 217

External 217

Internal 222

Middle 219

Foreign bodies in 225

Drum of the 219

Bones of the 220

Ear-sand 223

Ear-stones 223

Ear-wax 219

Eggs 68

Composition of 68

Emulsion of fats, in digestion 95

Enamel of the teeth 82

Epiglottis 126, 229

Uses of 126, 2->0

Eustachian tube 221

Exercise 30

Different modes of 31

Effects of 30

Importance of. 30

Open-air •.

Expiration 128

Movements of. 12!)

Extensor muscles 2(»

Eve 198

Eyeball 20=3

Eyelashes 200

Eyelids 200

F.

Fats 59

Emulsion of 59

Source of, in food 59

Fenestra ovalis 224

Fibres, Muscular 25

INDEX.

267

PAGE

Fibres, Nervous 149

Fibrine in food 58

of the blood 102

Fish, as food 71

Flexor muscles 20

Food 53

Animal . 07

Dai ly quantity of. 65

Ingredients of. 54-62

Necessity for 64

Source of 53

Vegetable 71

G.

Gall-bladder 95

Ganglia, cranial. Functions of the. . 171
Gases, Interchange of, in the lungs. 134

Gastric digestion 93

Gactric juice 91

Action of. 93

Daily quantity of. 92

General sensibility 179

Glands, Perspiratory 45

Salivary 86

Sebaceous 44

Glossary 252

Glosso-pharyn^eal nerve 189

Gullet 90

Gum.. 61

as food 62

Gustatory nerve 189

Gymnastics 33-38

for schools and colleges 33

Hair 42

Uses of 44

Hearing, Sense of 215

Protection of 2->4

Heart 107

Cavities of the 109, 110

Circulation through the 112

Frequency of action 112

Movements of the Ill

Valves of the .. 112

Heat, Animal 143

Production of 143

Regulation of 145

Hemiplegia 165

Humor, Aqueous 210

Crystalline 209

Vitreous 210

Hunger 65

Seat of the sensation of 65

Hydra 149

Hydrophobia 169

Hygiene 1

Hyperopia 212

I.

Incus 220

Inorganic substances in food 54

Insalivation 86, 88

Insensible perspiration 46

PAGE

Inspiration 128

Intestinal juice 95

Action of 96

Intestines 94

Complete digestion in. the small.. 94

Villiof the 96

Iris 205

Function of 205

Iron 56

Proportion in the blood 57

Proportion m the food . 57

J.

Joints 19

Varieties of 20

Juice, gastric 91

Intestinal 95

Pancreatic... 95

Labyrinth 222

Lachrymal canals 201

gland 201

Lacteals 96

Absorption by 96

Lactic, acid in gastric juice 92

Lactometer 68

Large intestines 94

Laryngoscope 231

Larynx 125, 228

Production of the voice in the. 126, 228

Lens, crystalline 209

Ligaments 19

Light, theory of 197

Lime in the bones 16

in the food 56

Importance of 56

Liver 95

Secretion of the 95

Locked jaw 169

Long-sight , 212

Lungs 123

Capacity of 130

Structure of 125

Lymph 97

Lymphatic vessels 97

M.

Magendie, on pain 181

Magnesia. Compounds of, in food... 57

Malleus 220

Marrow of the bones 17

Mastication 82

Importance of 88, 89

Meats 68

The cooking of. 69

The preservation of 69

Membrane of the tympanum 219

Medulla oblongata 154

Function of the 171

Microscope 236

The value of the 236

Simple 237

Compound 239

The use of the... 239

268

INDEX.

PAGE

Milk 68

Composition of 68

Specific gravity of :... 68

Milk-teeth 82

Mucous membrane of air passages. 127

Muscles 25

Function of the 25

Flexion and extension of 26

Voluntary and involuntary 26

Muscular contraction 27

fibres 25

sense 188

Myopia 212

N.

Nails 42

Uses of the 44

Nasal cavities 192

duct • 201

Nerve, Auditory 222

Glossopharyn-real 189

Gustatory ~ 189

Olfactory 193

Optic 197

Sympathetic 158

Nerve cells 150, 159

Nerve fibres 149

Nerves, Cranial 154

Spinal _ 156

Functions of the 160

Sensory, functions of the KiO

Motor, functions of the 160

Sympathetic system of 158

Nervous system 148, 149

Cerebro-spinal 150

Nervous tissue, Properties of 159

Nose 192

Nutrition, Processes of 80

O.

(Esophagus 90

Oil, Sources of, in food 59

Old-sight 215

Olfactory nerve 193

Optic nerve 197

Orbicular bone 220

Orbit of the eye 199

Organic substances as food 57 — 62

Organs of circulation 107

Digestion 81—91

Respiration 123

Sight : 198

Voice 228

Oxygen 131

Amount of, consumed in respira-
tion 132

Continually supplied to the atmo-
sphere 141

P.

Pain, Relations of, to pleasure 181

Sensation of 180

Uses of , 180

Pancreatic juice 95

Usesof 95

PAGK

Pancreatin 95

Paraplegia 163

Parlor gymnasium 36

Passages, Air 125

Pelvis 19

Pepsin 92

Peristaltic action of the stomach.. 92

Peritoneum 94

Perspiration, Daily amount of 46

Sensible and insensible 46

Uses of 46, 145

Perspiratory gland? 45

Physical strength 29

Culture 33

Physiology 11

Animal 11

Comparative 11

Human 11

Vegetable 11

Pia mater 152

Plasma of the blood. 102

Pleura *. 124

Pleurisy 128

Pneumo gastric nerve 171

Pneumonia 128

Poisons and their antidotes 247

Potash in the blood 57

Potato.. . 73

Presbyopia 215

Preservation of the teeth 85

Ptyalin 88

Pulsation of the heart 113

of the arteries 116

Pulse 115

Form of the 116

Writer 116

Pylorus 90

R.

Radial artery 110

Red corpuscles of the blood 102

Reflex action of the spinal cord . . . 165

Requisites for 167

Usesof....: 167, 170

Causing convulsions 169

Objects of 170

of the brain 174, 175

Rennet 58

Respiration 123

Change of blood in 123—133

Frequency of 129

128
123
123
135
33
206
207

Movements of.

Object of

Organs of

Respiratory labor.
Rest, necessity for

Retina

Retinal light

Ribs, Movements of, in respiration. 128

S.

Saccharine substances 60

Saliva 86

Importance of. 88

Secretion of 86

Salivary glands 86, 87

INDEX.

PAGE

Salt, Common 55

Importance of 56

Sclerotic coat of the eyeball 204

Sebaceous glands 44

Secretion of 45

Semicircular canals 223

Sensation of pain 180

Relations of, to pleasure 181

of temperature 187

of weisrht 188

Modification of : 178

Production of 177

Variety of 178

Sense of hearing 215

sight 196

smell 192

taste 189

touch 184

Sense, muscular 188

thermal 187

Senses, Special 177

Sensibility, General 179

Short-sight 212

Sinews 27

Sight, Sense of 196

Organs of 198

Skeleton 19

Skin 41

Structure of 41

Skull !. 19

Uses of the 19

Sleep, Necessity for 38

Amount required , 39

Small intestines 94

Smell, Sense of 192

Nerve of 193

Uses of 194

Soda in the food 57

Sound, Production of 215

Special senses 177

Spectroscope . . 104

Speech 227

Relation of, to the sense of hear-
ing 228

Sphygmograph 116

Spinal column 21

Spinal cord.. 155

Decussation of the 164

Direction of fibres in 164

Functions of the 162

Nerves of 156

Reflex action of 165

Spontaneous combustion 145

Stapes 220

Starch el

Its change into sugar 61

Different kinds , 61

Effect of boiling 61

Microscopic appearance 61

Stimulating substances 62

Stomach 90, 92

Digestion 93

Movements of 92

Secretion of 92

St. Vitus' dance 169

Sugar 60

Varieties 60

Sources of 61

PAGE

Sun-bath 59

Sympathetic system of nerves 158

Synovia 20

Systole of the heart m

T.

Taste, Association of 190

Education of. '. .' 191

Organ of 188

Sense of 189

Tea, Effect of 76

Kinds of 1b

Tears 201

Escape of the 201

Teeth 82

Temporary set of 82

Permanent set of 83

Bicuspid 83

Canine , 83

Incisor 83

Molar 84

Arrangement of 85

of different animals 85

Preservation of 85

Temperature of the body 140

Extremes of ' 146

Sensations of 187

Tendon of Achilles 27

Tendons 27

Tetanus 169

Thermal 50

Thermae sense 187

Thirst 65

Thoracic duct 97

Thorax 19

Thyroid cartilage : 229

Tissues, intimate structure of the. . 236

Human 244

of the lower animals 245

Tongue 188

Nerves of 189

Sensibility 189

Touch, Delicacy of 186

Organs of 183

Sense of 184

Trachea 125

Transfusion 106

Trichina spiralis 71

Trunk 19

Tympanum of the ear 219

Membrane of 219

V.

Valves of the heart. . . .. 112

of the veins 117

Vapor, Animal, in breath 132

Vegetable food 71

Vegetative functions 148

Veins 117

Valves of 117

Venous blood 135

Changes of, in respiration 133

Ventilation 142

Ventricles of the larynx 229

of the heart 110

Ventriloquism 235

270

I^DEX.

PAGE

Vertebrae 21

Vestibule of the internal ear 223

Villi of the intestines 96

Absorption by 96

Vital knot 171

Vitreous humor 210

Vocal cords 126, 230

Observation of, with laryngo-
scope 231

Voice 227

Organ of 228

Production of 232

Varieties of 233

W. PAGE

Water 74

Action of, on lead 75

Chemically pure 74

Croton 74

exhaled with the breath 132

from springs and well? 7i

Proportion of, in the blood 55

of, in the tissues and

fluids of the body 54

Ridgewood 74

Walking, as a means of exercise. . . 31

White corpuscles of the blood 104

Wisdom teeth 84

ANDERSON'S SCHOOL HISTORIES.

PRACTICAL- BOOKS BY A PRACTICAL TEACHER.

A Grammar-School History of the United States.

By JOHN J. ANDERSON, A.M., late Principal of Grammar School Nt
31, New York City; Author of a Manual of General History, A Picto-
rial School History of the United States, etc., etc. Illustrated with
more than 40 Maps. 16mo. 258 pages.

CHARACTERISTIC FEATURES. — 1. The narrative is written with great clearness and
conciseness, and is brought down to the present time. 2. Unimportant matters are en-
tirely omitted, or only incidentally alluded to. 3. The history and the geography are
taught together. 4. Th- hook is fully supplied with Maps, and the location of every
place mentioned is ace' ately shown. 5. All the proper names are accurately pronounced
in connection with th' lames as they occur. 6. The plan affords frequent and systemarfc
reviews by topics. Two entirely different sets of question^ run through the book.
8. It contains the Constitution of the United States, with full explanations and class-
exercises. 9. It contains Washington's Farewell Address. 10. It contains, at the close
of the book, a complete resume of the whole history, arranged for topical study and
recitation. 11. It contains but 260 pages. 1-2. It is sold at a moderate price.

The publishers believe that teachers who are tired of the cumbersome histories of our
country now largely in use, and desire a book with which they can produce satisfactory
results, will find that this work icill exactly meet their wants.

DEPARTMENT OP PUBLIC INSTRUCTION,

Superintendents Office, City of New York.

41 1 have carefully-examined Anderson's Histories, adopted by the Board of Education,
and used in the-Public Schools of this city, and cheerfully commend them to the favorable
regard of teachers and School officers, as well adapted to the purposes of instruction in
this branch of study, and as excellent and comprehensive compendium? of the leading
events of history." S. S. RANDALL, Svp't of Schools.

"Anderson's Histories have been in use in the Grammar Schools of this city from the
date of their publication, and, as far as I know, have given the highest degree of satisfac-
tion. They are written in a clear, concise style, are unusually accurate, and abound in
exercises which only a practical teacher could have constructed, and which make them
invaluable Class Manuals. They can scarcely fail to prove acceptable wherever practi-
cally tried." HENRY KIDDLE, Ass't Sup't of Scliools.

From Fifty -seven Principals of Grammar Schools in the City of Neio York.
"We are using Anderson's Histories in our school? with complete success. For class-
room instruction they are, we believe, superior to any other works on the subject with
which we are acquainted."

DEPARTMENT OP PUBLIC INSTRUCTION,

Superintendent's Office, Brooklyn.

"This is to certify that I am well acquainted with Anderson's Historic!-, they having,
been in the Public Schools of this city during the last three years. After having seen a
variety of works on the subject tried here, I am confident that ANDERSON'S are decidedly
the best for class-room instruction. They give the teacher just the aid he needs to
produce satisfactory results, and I therefore give them my unqualified recommendation."

J. W. BULKLEY, Sup't of Schools.

" Mr. Anderson has, I think, found the golden mean in nearly every feature that should
characterize a judicious school history."

JAMES CRUIKSHANK, AssH Sup't of Schools.

From the Principals of the Grammar Schools in the City of Brooklyn.

"It gives us pleasure, after using Anderson's Histories in our schools during the last

two years, to say that we like them. The plan of instruction, combining the geography

with the chronology of the narrative, is one which gives the books a decided superiority

over the works of other authors on the subject. Tfiey have our hearty commendation."

PUBLISHED BY CLARK & MAYNARD, NEW YORK.

36098

ANDERSON'S SCHOOL HISTORIES.

A School History of England.

Illustrated with Maps. By JOHN J. ANDERSON, A.M., Author of a
Grammar School History of 'the United States, a Pictorial School History of
the United States, a Manual of General History, etc., etc. 12mo. 302 pages.
Price $1.60.

1.— One of the aims of the author is to give not only the political and military history
of the country, but also to show its progress from time to time in civilization. 2. — The
pronunciation of proper names is given in connection with the names as they occur.
3.— In addition to the maps with the text, the work contains six finely engraved and
beautifully colored historical maps, showing the geographical changes in the country at
•different periods in its history. 4.— An Appendix contains an exposition of the leading
features of the English Constitution, and a geographical and historical account of the
British Possessions. 5. — The work ia fully supplied with Chronological and Genealogical
Table's, Biographical Notes, Subjects topically arranged by means of Review Questions
and«n Pronouncing Index. 6.— The volume embraces only 300 pages, and may therefore
be easily co

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"36

544488

UNIVERSITY OF CALIFORNIA LIBRARY

or tne biography of the mostaistinguislied men or tne couiur^ wnicii will
very much tend to excite a wish for additional reading and knowledge. A pretty
thorough examination of the work leads us to the opinion that its excellence leaves
little to be desired in a school history. If we could have had such a book at the right
time, in our school-days, it would have saved us a great deal of valuable time.
Frpm Prof. EBEN S. STEARNS, Principal of the Robinson Female Seminary. Exeter, N. H.
Prof. Anderson's History of England seems to me,-as the result of a close examina-
tion, eminently adapted to the school-room. Conscious, apparently, that a compend of
history must, from the nature of the case, exclude much of -"narrative and interesting
detail, the author has, with remarkable skill and judgment, stised upon the most salient
points and presented them in such appropriate and forcible language, and so happily,
that the student is beguiled through the driest abstractions, in this concise, yet vivid.
manner, all that is essential to a general knowledge of English history is ottered for study
within limits which can be readily conlpassed by the circumstances of most schools and
seminaries. The well drawn maps connecting geography with history, the carefully
arranged chronological tables with which the work abounds, and the pronunciation of
proper names constitute also distinctive, and most valuable features. The introduction
of dates, of course not to be dispensed with, has been so arranged as not to interfere
with the narrative, or-to unncessarily burden the student's memory. Certainly, no other
work of the kind, which I have ever examined, has impressed me so favorably as this ;
and I shall be much disappointed if it does not so commend itself to teachers as to
speedily obtain the very highest place among text-books.

Published by CLARK & MAYNARD, New York,