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Any of the above sent by mail, post-paid, on receipt of price. ELEMENTS 
OP THE 
Anatomy, Physiology, and Hygiene 
OP THE 
HUMAN SYSTEM. 
BY 
JUSTIN E. LOOMIS, LL.D.. 
• WAV ' ' 
President of the University at Lewisburg ; Author of the Elements of Oeology. 
REVISED EDITION. 
NEW YORK; 
SHELDON AND COMPANY, 
677 Broadway. 
1872. Entered according to Act of Congress, in the year 1871, by 
SHELDON AND COMPANY, 
In the Office of the Librarian of Congress, at Washington. 
The present edition has been revised throughout, but the only important 
changes have been in the chapter on digestion. The section on the individual 
muscles has been retained, but as an appendix. No considerable difficulty 
will be experienced in the use of this and former editions in the same class. 
Joseph J. Little, 
Stereotyper, Electrotyper, and Printer, 
108 to lit Wooster St., N. Y. CONTENTS. 
Introduction ...........7 
PAGE 
PART L—THE MECHANICAL SYSTEM. 
CHAPTER I.—Of the Bones . 11 
Section 1.—General Considerations on the Bones . 11 
Section 2.—Bones of the Head 17 
Bones of the Cranium . . . . 17 
Bones of the Face 26 
Section 3.—Bones of the Trunk 29 
Bones of the Spine 29 
Bones of the Thorax .... 37 
Bones of the Pelvis 41 
Section 4.—Bones of the Upper Extremities . . 43 
Section 5.—Bones of the Lower Extremities ... 47 
CHAPTER II.—Of the Articulations. ..... 51 
Section 1.—Parts of which the Joints are Composed . 51 
Section 2.—Particular Joints 57 
CHAPTER III.—Of the Muscles . . . .... 60 
Section 1.—General Description of the Muscles . . 60 
PART II.—THE NERVOUS SYSTEM. 
CHAPTER I.—Of the Brain, Spinal Marrow, and Nerves . . 74 
Section I.—The Brain 74 
The Membranes of the Brain ... 74 
The Structure of the Brain . . . 76 
The Functions of the Brain . , . .78 
Section 2.—The Spinal Marrow 87 
Section 3.—The Nerves . • 91 
The Cranial Nerves ..... 92 
The Spinal Nerves 94 
The Great Sympathetic Nerve ... 97 
The Functions of the Nerves . • .97 4 
CONTENTS. 
PAGE 
CHAPTER II.—Of the Organs of the Senses . . . . 106 
Section 1.—The Sense of Sight 106 
Section 2.—The Sense of Hearing .... 119 
Section 3.—The Sense of Smelling ..... 127 
Section 4.—The Sense of Tasting .... 130 
Section 5.—The Sense of Feeling 132 
CHAPTER I.—Of Digestion 142 
Section 1.—The Organs of Mastication and Deglutition 143 
* Section 2.—Thd Stomach 151 
Structure of the Stomach. . . . 152 
Thd Gastric Juice 153 
The Laws of Diet 156 
Section 3.—The Duodenum and Organs connected with it 165 
Section 4.—The Intestines 170 
CHAPTER II.—Of the Circulation 174 
The Organs of the Circulation. . . . 176 
The Forces of-the Circulation . . . .181 
, . The Object of the Circulation . . . . 184 
CHAPTER III.—Of Respiration 187 
The Organs of Respiration . . . . 187 
* * The Object of Respiration 194 
The Changes in the Blood by Respiration . 198 
The Vital Force , . . ... . . 199 
Animal Heat 201 
The Elements of Respiration and of Nutrition . 202 
CHAPTER IV.—Of Absorption 205 
CHAPTER V.—Of Secretion 208 
The Kinds of Secretion 208 
The Organs of Secretion 209 
The Relation of the Secreting Organs to each 
other 215 
CHAPTER VI.—Hygiene 216 
PART III.—THE REPAIRING SYSTEM. 
APPENDIX. 
Section 2.—The Muscles Individually. . . . 229 PREFACE. 
A knowledge of human Anatomy and Physiology is not confined 
to the medical profession, nor to professed scholars. It has become 
a part of general education, and is always attainable in our advanced 
schools, both public and private. The study becomes professional 
when it is pursued to minute details, hut the general structure of 
the body, the uses of the several parts, the conditions upon which 
their healthy action depends, and the circumstances by which such 
action may be interfered with, should be understood by all. The 
physical well-being of ourselves and of those with whom we stand 
connected, depends in a great measure upon our acquaintance with 
these laws of our organization. 
It is the design of the following work to present these principles 
in a form adapted to class instruction. 
The first object has been a suitable arrangement. Such an analy- 
sis of the objects and wants of the system is given as leads to an 
obvious classification of the organs of the body. This enables the 
learner to see at once what subjects are to be investigated, and in 
what order they naturally present themselves, and to know when 
his work is done. Until the facts of a science are thus arranged, 
upon some principle of relation, they do not constitute a science, 
and can serve no purpose either of practical application or of fur- 
nishing enjoyment or mental discipline. 
The Physiology and Hygiene of the several classes of organs arc 
so obviously associated with their structure, that it was thought 
better to introduce them in immediate connection with the ana- 
tomical descriptions. The repetition which would be almost neces- 
sary if they were treated in separate sections is thus avoided. 
Many subjects of collateral interest have been presented in the 
form of notes. This has been done in order that the consecutivo- 
ness of arrangement in the text might not be interfered with. 
The second object has been compression. It is one of the serious 
difficulties met with by teachers, that their text-books are not too 6 
PREFACE. 
comprehensive, but too large. In most of the branches of study, 
they should be of such size that they can be completed in a single 
term. And in addition to this, time enough should be allowed for 
thorough review. A subject that is worth studying is worth re- 
viewing. The principles should not only be understood, but they 
should be repeated so many times that they cannot be forgotten. 
Every scholar should become so familiar with the subjects of his 
study as to be able to take up any of the parts, and give a ready 
and intelligible account of it. 
Whenever conclusions rest upon reasoning which is complex and 
difficult, special effort has been made to render the expression of 
the reasoning as clear and little involved as possible. But to sim- 
plify and popularize it in any other way has not been attempted, 
nor would such a course be likely to secure for it additional favor. 
Hence, technical terms have not been discarded. In entering upon 
a new subject of study, the learner will necessarily meet with new 
terms, and it is best to employ those which express the ideas that 
are peculiar to the study with the greatest precision, and the least 
circumlocution. Science has a language in some respects peculiar 
to itself, and so has the counting-room and the farm. Each claims 
its own language, its technical terms, because the ideas to be ex- 
pressed are peculiar and require such terms. 
A glossary of technical terms has been combined with the index, 
and, as a matter of convenience to pupils, the pronunciation has 
also been marked. 
The several subjects are so fully illustrated by figures, that teach- 
ers, it is believed, will not find it necessary to avail themselves of 
anatomical plates to facilitate instruction. 
The author has endeavored to bring the important principles of 
extended treatises on these subjects into a sufficiently narrow com- 
pass, to divest them somewhat of the professional cast which they 
there assume, and put them into a form in which they will be intel- 
ligible to pupils, and to give them an arrangement that will show 
their connection with each other, as parts of a single branch of 
science. In attempting to do this he has been guided by his expe- 
rience as a teacher for many years. He now offers the work to the 
public in the hope that it will meet the approval of those to whom 
the instruction of youth is committed. 
New York, Jan. 1, 1853. ANATOMY, PHYSIOLOGY, AND HYGIENE. 
INTRODUCTION. 
1. It is the object of Anatomy to describe the human 
body, the structure, form, and position of its several or- 
gans. It is the object of Physiology to describe the uses 
and relations of these organs. It is the object of Hygiene 
to develop the principles upon which the healthy action 
of these organs depends. The three may be kept distinct 
as departments of professional study; but, as branches of 
general education, they are more conveniently studied 
together. 
2. In order to arrive ar a convenient classification of 
these organs, it is necessary to consider the object foi 
which the body is furnished. We, that is our minds, can 
exert no direct control1 over the material objects around 
1 This statement can scarcely need illustration. We cannot, for in. 
stance, by a mere exertion of the will, cause a hook which lies before us 
to change its place. Such change can be made only by the application of 
physical force. Perhaps we might have been so constituted that we could 
have controlled directly other matter, as we do our bodies ; but such power 
has not been given us, and those who pretend to possess it either deceive, 
in reference to the effect itself, or the effect is produced by the application 
of ordinary physical force, exerted in such a way as to elude our observa- 
tion. The most successful efforts of jugglery are of this last kind. The 
skill consists mainly in the power which performers acquire of moving the 
1. What is the object of Anatomy ? Of Physiology ? Of Hygiene? 
ft. Why is a physical system necessary ? 8 
INTRODUCTION. 
us. We do, more or less, control these objects; but it is 
by the body as an intermediate agent. How the mind is 
brought into relation with this portion of matter, the body, 
so that it acts in obedience to our wills, is unexplained and 
inexplicable. All that we can say of it is, that it has 
pleased our Creator thus to constitute us; and all the 
knowledge which we have of the external world comes to 
us by this connection of mind and body. 
3. Bearing in mind, then, that the body is furnished us 
as the means by which we may become acquainted with, 
and operate upon, external objects, we may inquire what 
kind of organization will secure this end. 
In the first place, there must be a suitable mechanical 
structure. It must be sufficiently firm to support the 
weight and transmit the power which the purposes of life 
require; and this firmness is secured by the framework of 
hones which the body contains. This framework must not 
be a rigid structure, but capable of various motions. The 
joints are provided, to render these motions possible ; and 
the muscles are the system of connections by which the 
several parts of the frame are acted upon in the perform- 
ance of these functions. 
As a system of mechanism, the body is no more capable 
of moving itself than any other piece of machinery is. In 
the second place, then, the mind, regarded as the reposi- 
tory of voluntary power, must have the means of applying 
hands with wonder ul accuracy, and yet with a rapidity so great that the 
eye cannot follow them. Thus, changes take place before the observer 
for which he can assign no cause ; but they are effected by the hand of the 
performer with a motion which is invisible only because of its rapidity. 
3. What are the three systems of organs by which the body is fitted to perform 
its functions ? Of what classes of organs does the mechanical system consist ? 
Why must there be a nervous system ? Of what classes of organs does it con- 
sist ? Why is a third system of organs necessary ? What objects are effected 
by the repairing system f INTEODUCTIOK. 
9 
its power. The. nervous system, consisting of the brain, 
the spinal cord, the nerves, and the organs of the external 
senses, are the means of applying this power to the me- 
chanical system, as well as the means by which the mind 
acquires a knowledge of the properties of matter. 
It would seem that when these two systems are formed, 
and so long as they remain perfect, no others are necessary 
to effect the purposes for which the body is designed. But 
a long process of growth is necessary to perfect the body; 
and, like all material structures, it is liable to become in- 
jured, and is subject to ultimate decay. It therefore be- 
comes necessary that there should be a third system of 
organs, which we may call the repairing system, designed 
to secure the growth which is required in the earlier pe- 
riods of life, and to furnish the repairs which are required 
at every period. 
4. Our investigation of this subject will, therefore, be 
limited to an examination of these three systems, of which 
the body is mainly composed: namely, the Mechanical 
System, the Nervous System, and the Repairing System. 
4 . To what will our study of this subject be limited? PART I 
THE MECHANICAL SYSTEM. 
THIS SYSTEM CONSISTS OF THE BONES, JOINTS, AND MUSCLES. 
Section I.—General Considerations on the Bones. 
CHAPTER I.—OF THE BONES. 
5. The principal object of the bones is to constitute 
the framework of the body. Its firmness, height, and gen- 
eral form depend upon them. They, however, serve other 
important purposes, particularly that of protection to some 
of the more delicate organs. Thus, the cranium is designed 
to render the brain secure from external injury, and the 
ribs are employed to form and protect the cavity in which 
the heart and lungs are lodged. 
6. It is interesting to trace the process by which 
the bones are developed. There is a period very 
early in our existence, but after the body has acquired its 
general form, when the skeleton contains no bone, but 
consists entirely of cartilage (gristle). These pieces of 
cartilage, which constitute the first draft of the osseous 
structure, are traversed by minute blood-vessels, and parti- 
cles of bone, conveyed by the blood, are deposited at points 
Section I.—5. What is the principal object of the bones? What other pur- 
poses do they serve ? 
(I. Of what is the first skeleton composed? State the process by which this 
is changed to one ol bone. How long time is required to make this change ? OF THE BONES. 
called centres of ossification, near the middle of each piece 
of cartilage, the corresponding cartilaginous particles being 
at the same time taken up by the circulating fluid, and 
carried away. 
Thus, by a very slow process, the original skeleton is 
taken down, and one of bone is built up.* Though ossifica- 
tion commences sometime before birth, it is not completed 
till about the twentieth year of life. In certain parts the 
change' is delayed much longer. Thus, the lowest portion 
of the breast bone is generally cartilaginous till extreme 
old age, and the cartilages which connect the ribs with the 
breast bone, in healthy persons, never become ossified.3 
7. At the most vigorous period of life, when the bones 
have attained their full development, they contain about 
three-fifths of their weight of earthy matter, of which phos- 
phate of lime is the principal part, and the remaining two- 
fifths is animal matter, mostly in the form of gelatine.4 
2 When children have but little exercise, breathe impure air, or are con- 
fined to food containing but little nourishment, the process of ossification 
is often arrested; and as the body, which continues to increase in size, 
becomes too heavy to be supported by the cartilages, they yield, and 
permanent deformity results. 
3 When a bone has been broken, it does not unite by a sudden deposition 
of bone. There is a partial cure effected by a rapid deposition of cartilage 
between the broken surfaces, by which they are temporarily, though not 
very firmly, united. The complete ossification of this cartilage may re- 
quire several months. 
* These two parts may easily be exhibited separately. When a bone is 
thrown into the fire, the animal matter which is distributed through it 
becomes charred (converted into charcoal) by the heat, and it becomes 
black. The animal matter, however, soon burns out, and a white brittle 
substance, the mineral matter of the bone, is left. The bones would, 
7. What is the composition of the hones? How does their composition differ 
from this in early life? Why is a flexible state of the bones better adapted to 
the conditions of early life? What change ia the composition of the bones takes 
place in old age ? 13 
OF THE BONES. 
But their composition varies with a person’s age. Early 
in life, the animal matter predominates, and- the bones are 
tough and flexible, though possessing less of firmness. This 
is the reason why there are so few permanent injuries from 
the accidents of childhood and youth. In advanced life, 
the earthy matter predominates, and the bones become 
brittle, and, when broken, less disposed to unite firmly. 
8. The form of the bones is so various, that it can 
scarcely be employed in the classification.of them. Yet it 
is convenient to speak of long bones, as those of the leg; 
of flat bones, of which the cranium mostly consists; and 
of square bones, such as are found in the wrist and ankle. 
9. The structure of the bones is by no means as 
simple as it at first appears. When bone begins to be 
formed, the osseous particles are so deposited as to form 
fine, stiff threads of bone, and 
hence the long bones are always 
fibrous, and, for the same reason, 
bfines have a radiated 
structure. (Fig. 1.) ' ,. 
Kg. 1. 
The outside of .the 'body of 
the long bones is very dense and 
compact; but, at,a veK little 
distance, becomes 
porous, and the pores increase in 
size as they are situated further from the surface. Finally, 
Exhibiting the radiation of the 
flat bones. 
probably, become equally brittle during life if, by any vital process, they 
were as fully deprived of animal matter. 
If a bone be placed in dilute muriatic acid, the acid will, in a few days, 
combine with and dissolve the earthy part of the bone, and leave the 
animal part, which will have the exact form and size of the bone, but will 
be flexible like India-rubber. , 
8. What classification of the bones is made depending upon their forms ? 
9. How are the fibrous and radiated structures produced ? Where is the structure 14 
OF THE BONES. 
Fig. 2. 
the centre is hollow. The hollows of the 
bones are filled with marrow, and the cavi- 
ties of the porous portions are also filled 
with a fatty substance resembling marrow. 
By this arrangement, nearly as great strength 
is secured as would be if the whole were a 
mass of compact bone, while the weight is 
not more than half that of solid bone. 
The extremities of the long bones, 
also, have the porous structure, and are 
much larger than the middle portions, in 
order to give strength to the joints by pre- 
senting large articular surfaces. 
The substance of the bones is every- 
where (except in the teeth) traversed by 
blood-vessels, absorbents, and nerves, so that 
these solid parts are still living parts, and 
are continually undergoing the processes of 
removal and renewal, like the other parts 
of the body.5 It is by means of these tra- 
versing organs that the bones are able to 
unite when they have been fractured, or to 
be repaired when they have been injured by 
disease. 
Section of the thigh 
bone, a a The ex- 
tremities, show- 
texture6 *Trfe 
exterior of the bo- 
dy, of very dense 
bone, c The hoi- 
low of the bone, 
rowf "Ith mar 
It follows, that children should not, before the bones have acquired their 
strength, be subjected to the severer kinds of labor, such as require great 
firmness of frame. They should not be required to lift great weights, nor 
carry heavy burdens ; nor should they be confined, for a long time, to any 
one position. The restlessness of children is natural, and is designed to 
prevent the distortions of body which would be likely to result from a 
child’s maintaining habitually the same position, when the bones are so 
most compact ? What is the structure of the central portion of the bones 5 Of 
the extremities ? Why are the extremities of the bones enlarged ? With what 
are the cavities of the bones filled, and for what purpose ? What other organs 
are found penetrating the bones, and for what purpose ? OF THE BONES. 
10. The blood always contains, in solution, a small 
amount of osseous matter, and both the formation and 
growth of bones take place by the deposition of these 
particles of bone. The bones increase in diameter by the 
yielding as to allow of their readily taking any form which a constrained 
position would tend to give. 
Children at school often rest the elbows upon the table, and allow the 
headland chest to fall forward; they thus become round-shouldered 
Others acquire the habit of lounging, or of resting one elbow in such a way 
as to give a lateral curvature to the spine. The feeling of lassitude and 
weariness, which rapid growth is likely to induce, may encourage these and 
other objectionable positions which are liable to result in permanent de- 
formity. The upright erect position may be recommended as preferable, 
so far as it can be practised ; and yet this effort should not be carried too 
far, for, in the first place, to carry the head and shoulders too far back is 
as unnatural and as much a deformity as the opposite error; and, sec- 
ondly, the most natural erect* position will become injurious if persisted in 
to weariness. A large amount of exercise, and the frequent changes of 
position thus secured, are the best safeguards against all the deformities 
which are likely to be contracted in childhood. 
6 It will hereafter be shown that, by the processes of life, the soft parts 
are constantly undergoing removal and renewal. Portions of every muscle, 
for instance, are every moment undergoing chemical change, losing their 
vitality, and requiring removal from the system. At the same time, there 
is a renewal, by the deposition of new muscular fibre from the blood. 
These changes are essential to the continuance of life. It was discovered 
accidentally that the same changes take place in the bones. A dyer threw 
to some domestic animals madder from which most of the coloring matter 
had been extracted. Some of the coloring matter, however, remained, and 
upon killing the animals which had fed upon it, the bones were found to 
be tinged with it. Hence, there must have been, a deposition of the color- 
ing matter in the substance of the bone. By varying the experiment, feed- 
ing with madder, and then, for some time before killing, withholding it, 
the bones were found of the ordinary color; thus proving that the coloring 
matter which was at first deposited had been absorbed and removed. 
10. How is the osseous matter for the growth of the bones supplied ? How 
do they increase in diameter ? Why can they not increase in length in the same 
way ? How do they increase in length ? How long do the body and extremities 
of a bone continue unsolidified ? 16 
OF THE BONES. 
deposition of layers of bone upon the outside, similar to the 
successive rings oi growth in a tree: but their 
increase in length is by a different process. 
The ends of a hone are so much larger than 
the middle, and so different in shape, that the 
bone would be deformed if its elongation took 
place by deposition upon the ends. There is 
therefore a special provision for growth in this 
direction. A long bone has, at least, three 
centres of ossification : one for the formation 
of each extremity, and one for the formation 
of the body of the bone. So long as the bones 
are capable of elongating, the extremities of 
the bone are always separated from the body 
of it by sections of cartilage, as at a a, Fig. 3, 
and the bone increases in length by the de- 
position of bone at the ends of the body, thus 
pushing the extremities farther from each 
other. As soon as the body has fully ac- 
quired its growth, this section of cartilage 
becomes ossified.7 
Fig. 3. 
Bone of the arm. 
11 Body of the 
bone. 2S The 
extremities 
(epiphyses) a 
a Layers of 
cartilage, by 
which the bo 
dy and epiphy- 
ses are coo 
nected. 
II. A dense, tough membrane, called the 
periosteum (bone envelope), surrounds the 
bones, except at their extremities. It serves 
to protect the bone, to supply it with its 
nerves and blood-vessels, and is the means by 
which the ligaments, tendons, and muscles 
are attached.8 
6 The experiment in' the preceding note was varied by feeding an animal 
that was growing rapidly with madder, for a few days, and then withhold- 
ing it. The bone which was formed while the blood was charged with the 
coloring substance, would be more highly tinged than the bone previously 
11. What is the periosteum 5 What purposes does it serve} Into what lour 
classes are the bones divided i BONES OF THE HEAD. 
17 
The bones are divided into four classes: those of the 
head, those of the trunk, and those of the upper and of the 
lower extremities. » 
Section II ~ Bones of the Head. 
The bones of the head include those of the cranium and 
those of the face. 
I. Bones of the cranium. 
12. The bones of the cranium are composed of external 
and internal plates, and an intervening porous portion, 
answering to the hollow and the porous structure in the 
long bones, called the diploe. The external plate has the 
formed would become by deposition of coloring matter into the interstices. 
The bones of the animal were found, upon examination, to consist of con- 
contric lamina; of more highly and less highly colored hone, showing that 
the bone was formed by successive depositions upon the outside. 
7 If too much or too severe labor be required of an individual while these 
cartilages remain, and the body is forming, nature attempts to secure the 
system against injury by a more rapid ossification of them than would 
otherwise take place. Thus they may become bone before the body has 
acquired its full development. But it is impossible that any further growth 
of body should take place, and a dwarfed stature is the result. There are, 
however, other causes of such a stature. It may result from too little exer- 
cise in early life, or from disease, or it may be hereditary. 
8 This membrane, though ordinarily possessing but little sensibility, is 
sometimes subject to inflammation, when it becomes intensely painful The 
felon and fever sore are diseases originating in this membrane. Disease 
seldom attacks the bones directly; but it may be communicated to them 
either from the periosteum, or from the investing cartilage where this mem- 
brane is wanting, as in the joints. 
Section II.—What do the bones of the head include ? Name the bones of the 
cranium. 
12. Of what three parts do the cranial hones consist? Describe each part. 18 
FRONT VIEW OF THE SKELETON, 
Fig. 
The Skeleton consists of 201 
bones. In this enumeration the 
teeth, the hyoid bone, and the 
bones of the ear are not included. 
Certain bones in the sutures of 
the head, and in some of the 
joints, which, though generally 
present, are not regarded as es- 
sential parts of the framework, 
are also omitted. 
NAMES AND CLASSIFICATION OF 
THE BONES. 
1. The frontal bone, . . 1 
2. The parietal bones, . 2 
3. The occipital bone, . 1 
4. The temporal bones,. 2 
The sphenoid bone, . 1 
The ethmoid bone, . 1 
Bones of the Cranium 8. 
5. The nasal bones, . , 2 
The lachrymal bones, 2 
6. The upper maxillary 
bones, 2 
Bones of the Face 14. 
7. The malar bones, . . 2 
The palatine bones, . 2 
The lower spongy 
bones, 2 
8. The lower maxillary 
bone, 1 
The vomer, , . . . 1 BACK VIEW OE THE SKELETON. 
19 
Fig. 5. 
9. The vertebras, . 24 
10. The sternum, . 3 
11. The ribs, ... 24 
12. The ossa inno- 
minata, ... 2 
13. The sacrum, . . 1 
14. The coccyx, . . 1 
Bones of the Trunk 55. 
15. The scapula,. . 2 
16. The clavicle,. . 2 
17. The humerus, . 2 
18. The ulna, ... 2 
19. The radius, . . 2 
20. The carpal bones, 16 
21. The metacarpal 
bones, ... 10 
22. The phalanges, . 28 
Bones of the Upper Extremities 64. 
23. The femur, . . 2 
24. The tibia, ... 2 
25. The fibula, . . 2 
26. The patella, . . 2 
27. The tarsal bones, 14 
28. The metatarsal 
bones, ... 10 
29. The phalanges,. 28 
Bones of the Lower Extremities 60. 20 
BONES OF THE HEAD. 
toughness and hardness of ordinary bone; the internal, 
called the vitreous plate, is much harder. The bones of 
the cranium are eight in number. 
13. The frontal bone (1, Fig. 6; 1,1, Fig. 7) occu- 
pies the region of the forehead, and extends from the top 
of the head forward to the eyes and nose, and laterally 
about half-way to the ears. On the forehead, the two 
plates of the hone are considerably separated from each 
other, leaving the cavities above the eyes called the frontal 
sinuses. The external plate terminates at the ridge upon 
Which the eyebrows are situated, while the internal plate 
Fig. 6. 
Bones of the Cranium, separated. 1 The Frontal hone. 2 The Parietal hone. 3 
Occipital bone. 4 The Temporal bone. 5 The Nasal bone. 6 The Malar bone. 
13. What is the situation of the frontal bone? How are the frontal sinuses 
formed ? Of what does the orbital plate consist, and how is it situated ? BONES OF THE HEAD.’ 
21 
turns backward, forming the upper part of the orbit of the 
eye. This is the orbital plate of the frontal bone, and be- 
comes the floor upon which the front lobe of the brain rests. 
14. The parietal bones (2, Fig. 6) are two square, 
smooth bones, situated directly back of the frontal bone, 
united together at the top of the head, and forming the 
highest and the lateral portions of the cranium. 
15. The occipital bone (Fig. 8; also 3, Fig. 6) forms, 
as the name indicates, the back part of the cranium, as 
well as the floor on which the posterior lobe of the brain 
rests. In the base of the bone is a large aperture, the 
magnum foramen, through which the spinal cord is con- 
nected with the brain. On the under margin of this fora- 
men are two prominences, called condyles (button-shaped 
elevations), which contribute to form the joint between the 
head and spine. 
16. The temporal bones (4, Fig. 6) are two irregu- 
larly shaped bones reaching downward from the parietal 
so far as to contain the cavity of the ear, then inward to 
within an inch of each other. Above the ear they are 
very thin. The portion which forms part of the base of 
the cranium, and within which the principal parts of the 
organ of hearing are situated, is called the petrous (stone- 
like) portion, and is very thick and hard. 
They have three well marked processes: the mastoid 
process (1, Fig. 9), situated just back of the ear; the 
styloid process (2), a long, slender projection, near the 
mastoid, reaching down the side of the neck; and the 
zygomatic process (3), which rises forward of the ear, 
passes over the temporal muscle (4), and connects with 
14. Describe the parietal bones. Why are they called parietal ? 
15. What is the meaning of occipital? How is the occipital bone situated? 
What foramen is found in it ? Where and for what purpose are the condyles ? 
16. Describe the temporal bone. Its processes. 22 
BONES OF THE HEAD. 
another process of the same name from the cheek-bone. 
Between the styloid and mastoid processes is a small open- 
ing in the bone (9), called the stylo-mastoid foramen. 
17. The sphenoid bone. (Fig. 10.) This is a bone 
of a very irregular shape, and has, with some degree of 
propriety, been compared to a bat with its wings extended. 
The body (1) is situated in the centre of the base of the 
cranium. Large processes (2, 2), called the great wings, 
extend up so far as to articulate (at 3, 3) with the frontal 
bone. There are two pterygoid processes (4, 4) on each 
side, reaching downward from the body of the bone, and 
situated directly back of the throat. They support the 
pharynx, and give attachment to several muscles of the 
neck. 
Fig. 7. 
Fig. 8. 
The Occipital Bone. 1 The vertical portion, 
forming the back part of the Cranium. 
2, 2 The horizontal portion, on which the 
back part of the brain rests. 3 The Mag- 
num Foramen. 4 The ridge on the inner 
side of the bone, to which the Falx Cere- 
belli is attached. 5, 5 The ridge to which 
Tentorium is attached. 
The Cranium as seen from above. 1,1 
The Coronal Suture. 2 The Sagit- 
tal Suture. 3, 3 The Lambdomal 
Suture. 
18. The ethmoid bone (sieve-like) has a nearly cu 
17. Describe the sphenoid bone. 
18. Describe the ethmoid bone. BONES OF THE HEAD. 
bical form, and is situated between the orbits of the eyes, 
directly in front of the body of the sphenoid bone. The 
upper plate is riddled with holes, which give passage to the 
branches of the olfactory nerves, and the lower portion is 
cellular, reaches down into the nose, and is an important 
part of the organ of smell. 
19. The cranium, consisting of the eight bones which 
have now been described, has an ovoid form, flattened at 
the sides, and with the larger extremity backward. (Fig. 7.) 
In the base there are on each side three depressions, called 
the anterior, middle, and posterior fossce. 
20- The head of an adult person seems to consist of but 
one bone. In early life, however, the eight bones are not 
only distinct, but they are separated by a considerable width 
of cartilage (as seen, though with some exaggeration, in 
Fig. 6). The portion of cartilage which covers the soft 
spot on the top of the child’s head, remains unossified for 
several years. This intervening cartilage, like that which 
separates the body and epiphyses of the long bones, is de- 
signed to provide for the growth of the cranium, as the 
inclosed brain requires increase of size. When the growth 
of the brain is completed, the ragged edges of the contigu- 
ous bones nearly touch, and the projecting fibres interlock 
(as represented in Fig. 7) in such a way as to make an im- 
movable and very firm joint, called a suture. Yet the 
bones do not then come into actual contact; there is still an 
interposed layer of cartilage till after the meridian of life, 
when the cartilage begins to ossify, and the several bones 
of the cranium are at length consolidated into one. The 
coronal suture (1, 1) separates the parietal bones from 
the frontal bone; the lambdoidal suture (3, 3) sepa- 
19 What is the form of the cranium ? Describe the base. 
20. What is a suture ? Why are not the bones joined firmly together in early 
life? When do the sutures become obliterated? Name the principal sutures, 
and give their position. BONES OF THE HEAD. 
rates the parietal bones from the occipital bone. The 
sagittal suture (2) separates the parietal bones. The 
squamous sutures separate each temporal bone from 
the adjacent parietal bone.9 
21. Various parts of the system are designed, more or 
riff. 9. 
1 The Mastoid Process. 2 The Styloid Process. 3 The Zygomatic Process. 4 
The Temporal Muscle, passing under the Zygomatic Process, and inserted into 
the Coronoid Process, 5, of the lower maxillary bone. 7 The Condyloid Pro- 
cess of the lower maxillary. 8 The Ear. 9 the Stylo-mastoid Foramen. 
8 There are several other sutures in the cranium, but they are not easily 
described without a skeleton. 
The coronal suture is so named “ from being near the part upon which 
the victor’s crown (corona) was placed, in the games of the ancients the 
lambdoidal, from its resemblance in form to the Greek letter lambda; the 
“ sagittal, from its direction backward, straight as a dart” (sag'tta, an ar- 
row) ; the squamous (squama, scale), from the scale-like overlapping of 
the temporal upon the parietal bone. 
21. Name the four ways in which the cranium protects the brain against BONES OF THE HEAD. 
less directly, to protect the brain, but the cranium has this 
as its special object. The brain is a soft, yielding mass, 
and would be easily broken down and destroyed if it were 
not well protected. The substance of which the cranium 
consists, furnishes, by its hardness, a better protection than 
any other tissue would. The back of the head is most 
exposed to injury, either from accident or from malicious 
design, and accordingly the cranium has here the greatest 
thickness, while the sides of the head, which, in conse- 
quence of the position of the arms and shoulders, could 
scarcely receive any injury, are so thin as to be almost 
transparent. The arched form of the head enables it 
to resist the effect of blows more successfully than any 
other form. Pressure upon the top of the head would 
cause it to yield first at the sides, and this is prevented by 
the temporal bones coming up outside of the parietal, 
forming the squamous suture. 
Fig. 10. 
The Sphenoid Bone. 1 The hody. 2, 3 The wings. 4, 4 The Pterygoid Pro- 
cesses. 5, 5 The superior Foramen Lacerum. 
But violent jars and concussions are more likely to be 
permanently injurious than wounding the brain, or even 
wounds. In what other way may the brain be injured ? How are concussions 
absorbed before reaching the bone ? How in passing through the bone ? How 
is their continuance around the head prevented ? How many bones compose 
the face 1 26 
BOXES OF THE HEAD. 
removing portions of it. The cranium is well fitted to 
furnish protection in this respect also. It is covered with 
hair, with the general integument of the body, with mus- 
cles over a portion of its surface, and with the periosteum, 
through all of which the violence of concussions must ex- 
tend before the outer plate of the cranium is reached. 
Then, between the external and internal plates, is inter- 
posed an elastic cushion, the diploe, by which concussions 
upon the outer plate wTiil be partially absorbed before 
reaching the inner plate. Vibrations communicated to 
any one bone are prevented from continuing around the 
head by the cartilages interposed at the sutures.10 
II. Bones of the face. 
The face is composed of fourteen bones, two of which 
are single, the other twelve are in pairs. 
rig- 11. 
A vertical section of the hones of the face, a little forward of the ears. 1, 1 Lower 
spongy bones. 2. 2 The middle spongy bones. 3, 3 Superior spongy bones. 
4 Antrum Mnxillare. 
10 The cranium presents a fine instance of the adaptation of the system 
to the circumstances in which it is placed at the different periods of life. 
In early infancy the cartilages are so wide and flexible that the form of 
the head may be considerably changed without injury, a fact upon which, 
at certain crises, the continuance of life often depends. BOXES OF THE HEAD. 
27 
22. The nasal bones (5, Eig. 6) form the upper part 
of the nose, and articulate with the frontal and upper 
maxillary bones. 
23. The lachrymal bones (8, Fig. 6) are situated in 
the orbits of the eyes, near the internal angle. They con- 
tain grooves for the passage of the lachrymal ducts, from 
which the bones receive their name. 
24. The upper maxillary bones (7, Fig. 6) form a 
large part of the mouth and face. They inclose the large 
space on each side between the orbit of the eye and the 
roof of the month (4, 4, Fig. 11), called the antrum max- 
Children are constantly receiving falls, blows, and thumps, in conse- 
quence of the incautiousness and recklessness natural to that period of 
life, which would be unsafe at a later period, but which seldom injure the 
brain, because the cranium is yet in so yielding a state as to absorb the 
motions which they impart. But while nature has thus interposed to pro- 
tect the child, in a great measure, from the evils which his inconsiderate- 
ness would otherwise bring upon him, there is still a certain amount of 
care required on his part. The various plays, such as ball, goal, etc., which 
combine amusement and exercise, are therefore greatly preferable to tricks, 
summersets, wrestling, etc. 
In manhood, the cranium remains in part cartilaginous, not so much so 
as to unfit one for the vigorous activities of life, and yet so far so as to 
interpose something of security against accidents. This security is much 
less, however, than it was in childhood ; because a greater degree of care- 
fulness and forethought has rendered such security less necessary. 
In advanced life, the cartilages all become ossified; but at this period 
of life, also, severer labors are laid aside, and cautiousness of character 
begins to predominate, so that the brain needs fewer safeguards. 
This is probably a reason why aged persons are often so averse to noise, 
to the prattle of children, etc. It may be peevishness, second childhood. 
It may, often probably does, arise from those physical changes in the 
structure of the cranium, by which the brain is affected sensibly, perhaps 
painfully, by the vibrations of the air. 
22. Describe the nasal bone. 
23. The lachrymal bone. Why is it so named? 
24. Describe the upper maxillary bone. Where is the antrum maxillare situ- 
ated ? Name and describe the five processes of this bone. illare. These bones have several processes. The nasal 
process passes up along the side of the nose to the frontal 
bone; the orbitar process forms the base of the orbit of 
the eye; the malar process articulates with the malar 
bone; the palatine process forms the fore part of the roof 
of the mouth; the alveolar process is the projection in 
which the teeth are imbedded. 
BONES OF THE HEAD. 
25. The malar bones (6, Fig. G) are the large square 
bones which form the prominences of the cheeks; they 
also form part of the orbit of the eye. 
26. The palatine bones form the back part of the 
roof of the mouth. Processes extend up from these bones 
into the nose, and form part of the organ of smelling. 
27- The lower spongy bones (1, 1, Fig. 11) consist 
each of a very thin plate, which lies rolled up, and is at- 
tached to the side of the antrum maxillare. 
Fig. 12. 
The Lower Jaw. d The Condyloid Process, e The Coronoid Process. 
28. The vomer is the thin flat bone that divides the 
nostrils from each other. 
25. The malar bone. 
26. The palatine bone. 
27. The lower spongy bone. 
28. The vomer. BONES OF THE TRUNK. 
29 
29. The lower maxillary bone (9, Fig. 6) forms the 
lower jaw. It has three processes: the alveolar process, in 
which the teeth are set; the coronoid process, which is the 
sharp point at the extremity of the bone (e, Fig. 12) for the 
insertion of the temporal muscle ; and the condyloid pro- 
cess (d), by which the lower jaw articulates with the tem- 
po ral bone. 
Fig. 13. 
30. There is one other bone, the os 
hyoides (Fig. 13), which, though not 
one of the bones of the face, may be 
described with them. The front part 
of this bone (a), called the body, is at 
the root of the tongue. The two pro- 
cesses (h), called its cornua, reach back 
on the sides of the tubes which com- 
municate with the stomach and lungs. This bone is the 
centre of all the motions of the throat and tongue. 
The Hyoid hone, a The 
body, b The Cornua. 
Section III.—Bones of the TrunTc. 
They are the bones of the spine, of the thorax, and of 
the pelvis. 
I. Bones of the spine. 
31. The spine (Fig. 14) is a nearly vertical column, 
consisting of the sacrum (4, 5) as its base, upon which are 
piled twenty-four bones, called vertebrae, and below which 
is the small terminal bone (5, 6), called the coccyx. The 
29. The lower maxillarv bone. Describe its processes. 
3C. What other bone is described ? How is it situated, and what is its use ? 
t :on HI.—How are the bones of the trunk divided ? 
31. Describe the spine. Into what three classes are the vertebrae divided, and 
how is each class situated ? 30 
BONES OF THE THUNK. 
The Spinal Column. 1. 2 Cervical vertebrae. 2. 3 Dorsal ver- 
tebrae. 3. 4 Lumbar vertebrae. 4. 5 The Sacrum. 5, (i The 
Coccyx; there are often several coccygeal bones. 
Fife 14. BONES OF THE TRUNK. 
seven highest vertebrae (from 1 to 2) are in the neck, and 
are hence called cervical vertebrae; twelve are in the back 
(from 2 to 3), and are called dorsal vertebrae; and the re- 
maining five (from 3 to 4) are in the loins, and are called 
lumbar vertebrae. 
82. A vertebra (Fig. 15) is composed of a body and 
seven processes. The body (a) is the front part of the 
vertebra, of cylindrical form, and of spongy texture, hav- 
ing its uppeT and lower bases nearly flat, and composed of 
more solid bone. The processes are situated on the back 
part of the body of the vertebra. There are four oblique 
processes {h h), (sometimes called articulating processes), 
one above and one below, on each side. The transverse 
processes (d d), one on each side, project laterally from 
between the oblique processes. The spinous process (e) 
projects from the middle of the bone backward. 
Fig. 15. 
Fig. 16. 
The body of a Cervical Vertebra. 
2 The canal. 3. 3 The oblique 
processes. 4 The spinous pro- 
cess with its cleft extremity. 
a The body of a Vertebra, e The spinous 
process, dd The transverse processes. 
bb The oblique processes. / The spinal 
canal. 
32. Of what is a vertebra composed ? Describe the body of a vertebra. Where 
are the processes situated How many kinds are there ? Give the position of 
the oblique ; the transverse; the spinous. BONES OF THE TRUNK. 
33. The vertebras, in different parts of the spinal column, 
present great differences of form. The bodies of the cervi- 
cal vertebras (Fig. 16) are small, and so articulated as to 
allow great freedom of motion. The atlas (Fig. 17) is 
the first cervical vertebra. There are two faces {b b) on 
the upper side, adapted to the condyles of the occipital 
bone of the cranium; these constitute the joint which 
allows the vertical, nodding motion of the head. The pro- 
cesses, with the exception of the transverse, are scarcely 
developed. It has, properly, no body; but, in its place, 
Mg. 17. 
Mg. 18. 
The Atlas, b b The depressions for 
receiving the condyles of the oc- 
cipital bone, c c The transverse 
processes. Between/and/is a 
strong ligament by which the 
dentatns is prevented from press- 
ing upon the spinal marrow. 
The Axis, a The dentatus, a pro- 
longation of the body upward 
through the hole g, in the Atlas, 
Fig. 17. 
there is a hole (g)—or rather, an enlargement of the spinal 
canal, and separated from it by a strong ligament—for the 
reception of a process from the next vertebra below. 
The second vertebra of the neck is called the axis. 
The body of this vertebra is prolonged upward into a 
tooth-like projection (a, Fig. 18), called the dentatus, 
which is fitted to the corresponding opening (g) in the 
33. What is the peculiarity of the cervical portion of the spine? Describe the 
atlas; the axis. What is the peculiarity of the dorsal portion ? What of the 
lumbar vertebrae? What is the arrangement of the oblique processes of the lum- 
bar vertebrae ? Why is any special protection necessary in this part of the spine ? 
In what does this protection consist ? What part of the spine is most liable to 
injury ? BONES OF THE TRUNK. 
33 
atlas, and becomes the pivot on which the horizontal mo- 
tions of the head are performed. 
The dorsal vertebrae (Fig. 19) are larger than the cervi- 
cal, and the oblique processes are so arranged as to allow 
of but little motion in this part of the spine. The spinous 
processes also, which are very long, project downward upon 
the next vertebrae, so as to bind them together, and limit 
their motions to a very small amount*: 
Fig. 19. 
Fig. 20. 
A Dorsal Vertebra. 2 The 
body. 7, 7 The notches to 
form the intervertebral fora- 
mina. 3 The spinous pro- 
cess, very long and very much 
inclined. 
A Lumbar Vertebra, a The body, b The 
spinous process, c c The articulating 
(oblique) processes, d d The interver- 
tebral notches. 
The lumbar vertebrae (Fig. 20) are the largest in the 
spine. The upper oblique processes (c) form two pillars, 
between which are fitted so deeply the lower oblique pro- 
cesses from the next vertebra above, that dislocation is 
impossible without violence sufficient to break the pro- 
cesses. In this part, the spine, which has to support most 
of the weight of the body, is not assisted by any other part 
of the skeleton, and very free motion being required, every 
possible means is resorted to, to increase its strength, by 
increasing the size of the vertebrae, by binding them to- 
gether with ligaments, by interlocking their oblique pro- 
cesses, and by attaching muscles, which act as stay-ropes, 
to the projecting spinous and transverse processes. Still, BOifES OF THE TEUHK. 
this is the least protected part of the spine, and most fre- 
quently suffers injury. 
34. The faces of the adjacent vertebrae do not come into 
actual contact, but are separated by the intervention of an 
elastic substance (2, Fig. 21) resembling cartilage. 
35. The notches in the vertebrae, as seen at 7, Fig. 19, 
form, when the vertebrae are placed together, the openings, 
as seen at 1, Fig. 21, called the intervertebral fora- 
mina, through which .the spinal nerves pass out from the 
spinal cord. 
36. The processes are so arranged that a tube (/, Fig. 
15) passes through each vertebra, and as the bones are 
placed one upon another, these tubes become continuous 
through the spinal column, and form the spinal canal 
(c d, Fig. 14), in which the spinal cord is lodged. 
37. The spine serves several distinct purposes. In the 
first place, it is the framework, the axis of support of 
Fig. 21. 
Fig. 22. 
Fi°- 21 Two Vertebrae 3 3. 2 The intervertebral substance between them. 1 
The intervertebral foramen. Fig. 22. . Two Vertebrae, with the lorm ol the 
intervening carriage produced by bendimr the spine. 
34. By what are the vertebrae separated ? 
35. How are the intervertebral foramina formed? What is their use? 
36. How is the spinal canal formed? What is its object? 
37. What is the first purpose which the vertebral column serves ? What is the BONES OF THE TRUNK. 
35 
the trunk.1’ For this purpose, great firmness is required, 
the general provisions for which have been referred to in 
describing the lumbar vertebras. 
In the second place it must be so constructed as to al- 
low great freedom of motion. The provision for bending 
the body backward, forward, and to either side, consists in 
the elasticity of the intervertebral cartilages. Each carti- 
lage is firmly attached to the faces of the vertebras between 
which it is placed, so that motion (excepting in the upper 
two joints) is not performed by the surfaces sliding upon 
each other, but by the compression of the cartilage on the 
other side (2, Fig. 22) toward which the flexion is made, 
and the slight thickening (1) of the same cartilage on the 
opposite side. The number of the joints is so great that 
the necessary flexibility is secured, while only a slight mo- 
tion at any one joint is required. When the body is turned 
horizontally without changing the position of the pelvis, 
the motion is performed by a slight twisting of the carti- 
lages; but this kind of motion is very limited.12 
11 It should not, however, he considered that the support which the 
head and trunk require is derived wholly from the firmness of the spine. 
The spine follows the back side of the trunk, and on the front side there 
is a succession of muscles from the neck to the pelvis. As the spine would 
prevent an undue bending of the trunk forward, so these muscles will not 
so far yield as to allow of an undue bending of the trunk backward. 
Moreover, as the whole space within the walls of the chest and abdomen 
is always filled, the trunk is, to a considerable extent, self-supporting; up- 
on the same principle that a bag filled with grain will stand erect and sup- 
port heavy weights in addition, though neither the grain alone nor the 
cloth alone, would retain such a position. 
12 There is an obvious tendency of the cartilages to resume their natural 
form when they have been pressed out of it; but they do not do it at once. 
A person’s height is diminished during the day by continuous pressure upon 
second ? How are the motions of flexion performed ? How .s horizontal motion 
performed? What is the third object of the spinal column? What are the lia- 
biaties to be provided against ? What is the security against compression of the 36 
BOXES OF THE TRUXK. 
In the third place, it must be so constructed as to fur- 
nish a passage for the spinal cord, which shall secure it 
against injury both from without and from the motions of 
the spine. So large a proportion of the spine consists of 
bone, that the walls of the canal will resist any compres- 
Fig. 23. 
Fig. 24. 
Distorted Spine produced by 
habitual elevation of one 
shoulder. 
1, 1 Two vertebrae. 3, 3 The correspond- 
in'? spinous processes. 2 The interver- 
tebral cartilage. 
the cartilages. It is recovered, however, during the night. But if they be 
thus pressed habitually, they do not readily react: and there is danger that 
they will at length cease to react at all. A constrained position thus habit- 
ually assumed is liable to produce a permanently distorted spine. Per- 
sons engaged in any employment which requires the spine to be thus bent, 
should assume the erect or opposite position as frequently as possible. 
Persons often raise one shoulder (generally the right shoulder) habitu- 
ally higher than the other. The active employments of life often require 
it. Children at school, if the tables are too high, will sit with the side at 
the table, and one arm elevated upon it. This position may he rendered 
necessary by the employment chosen ; but more frequently it becomes un- 
necessarily fixed as a habit, through inattention. A permanent inequality 
of the shoulders is thus produced, the spine becomes bent (Fig. 23) to adapt 
it to this position of the shoulders, and a corresponding change in the posi- 
tion ot the internal organs, often leading to disease, will follow. Special 
attention is directed to this deformity, because it is contracted by a large 
proportion of persons who have reached mature life. And young persons, 
by careful attention, will be able to correct the tendency to it. 
spinal cord ? What against fracture of the spinal column ? What against injury BONES OP THE TRUNK. 
37 
sion to which it is ever liable. The flexibility of the spine 
and the toughness of the cartilages render it much more 
secure against fracture than it would be if it consisted of 
solid bone. The only danger, then, to which the spinal 
cord could be exposed, must arise from the bending of the 
spine. The security here consists in that part of the canal 
which is formed of cartilages (2, Fig. 24) being larger than 
that formed by the bodies of the vertebrae (1,1). Compres- 
sion of the cartilages may cause them to bulge out beyond 
their natural position; but it will not be to such a degree 
as to make those portions of the canal smaller than the 
portions which are formed of bone. 
In the fourth place, the spinal column affords considera- 
ble protection to the brain against the concussions which 
it would receive, if the head were connected with the lower 
extremities by an axis of solid bone. The jar occasioned 
by walking and by many active employments, as well as 
the more violent concussions occasioned by accidents, by 
running, jumping, leaping from great heights, etc., are, to 
a considerable extent, absorbed by the compression of the 
intervening cartilages. But another and very important 
security against injury from these sources, is the curvature 
of the spine. By recurring to Fig. 14, it will be seen that 
there is a forward curve in the loins, and one in the neck, 
and these being the most flexible parts of the spine, easily 
allow an increased bending for a moment, whenever any of 
these concussions occur. Such bending would not take 
place in a straight column, and whatever force is necessary 
to produce it, would, without those curvatures, be so much 
additional concussion upon the brain. 
II. Bones of the thorax (Fig. 25). 
to ihe spinal cord, by the flexion of the spinal column ? What is the fourth object 
of the spinal column ? What does it protect the brain against ? How do the car- 
tilages furnish this protection ? How do the curvatures f 38 
BOXES OF THE TRUNK. 
38. The sternum (Fig. 2G) is the flat bone situated on 
the front side of the thorax. It is about eight inches in 
They are the sternum and the ribs. 
Fig. 25. 
Fig. 26. 
The Thorax, b b The Spine, a The Sternum. 
The Sternum. From c to g is 
the middle portion of bone. 
The apparent separation at 
d and e do not indicate sep 
rate bones. 
length, and consists of three pieces, of which the lower one 
is cartilaginous, except in very old age. Its object is to 
provide for the joining of the ribs, and to protect the cavity 
of the thorax from compression. 
39. The ribs (Fig. 27) are the twenty-four slender 
38. Describe the sternum. What is its use? 
39. Describe the ribs. How are the true and false ribs distinguished ? BONES OF THE TRUNK. 
39 
bones which protect the sides of the thorax. They extend 
from the spine around the body toward the sternum, and 
are lengthened out by cartilage to their sternal articulation. 
The upper seven on each side articulate with the sternum 
by separate cartilages, and are called true ribs. The re- 
maining five have their cartilages united into one, and are 
called false ribs. Frequently, however, the loAvest rib, and 
sometimes the lowest two ribs, are not connected to the 
sternum by cartilage, and are called floating ribs. The 
Fig. 27. 
One of the Ribs, a Articulation with the vertebra, c Articulation 
with the Transverse Processes. 
posterior end of each rib is fitted to a slight cavity in the 
corresponding vertebra, and is also attached by a distinct 
joint to the end of the corresponding transverse process. 
The ribs are considerably inclined, so that the anterior 
articulation is lower than the posterior. 
40. One object of the bones of the thorax is the pro- 
tection of the heart and lungs, the organs which they sur- 
round. 
But they have another object more indispensable, that 
of forming a cavity the size of which is not dependent upon 
the organs which it contains. The abdomen is another 
40. What are the objects of the bones of the thorax? How does the cavity ol 
the thorax differ from that of the abdomen ? Upon what does the process of res* 
piratiou depend ? Of what is the pelvis composed ? 40 
BONES OF THE TRUNK. 
closed cavity, similar in many respects to the thorax, hut, 
being surrounded only by muscles and membranes, it en- 
larges and contracts as the organs within it are more or 
less distended. The thorax, on the contrary, having its 
general form determined by a framework of bone, cannot 
contract beyond a certain amount, however much the or- 
gans within may become reduced, and it is capable of en- 
largement independently of the dimensions of the organs 
within. 
It is the power of enlarging and contracting this cavity 
at pleasure upon which the process of respiration depends.13 
When it is enlarged the air enters the lungs, and they in- 
crease in size so as to keep the cavity filled. The effort to 
contract the thorax compels a portion of the air to escape. 
This ingress and egress of the air is respiration ; but there 
are important chemical changes effected by it which, as 
well as the muscular apparatus by which it is performed, 
will be explained in connection with the description of the 
lungs.14 
13 It will be shown, in the chapter on the circulation, that the motion 
of the blood in the veins is also in a great measure dependent upon these 
changes in the dimensions of the thorax. 
14 This is not the proper place to consider fully the effects of certain 
habits of dress upon the function of respiration. There is no question 
but that the form may be to a great extent controlled by dress. The 
thorax, which, if allowed to take its natural form, would be represented 
by Fig. 28, may, by compression, be so reduced as to be correctly rep- 
resented by Fig. 29. 
And the effects of this compression upon health and the duration of 
life are necessarily considerable. The greatly reduced capacity of the 
chest is itself of the nature of disease, and it contributes more perhaps 
than any other habit to invite other diseases, particularly those of a pul- 
monary character, but also the whole train of dyspeptic and nervous 
diseases. 
But the influence of habit is not easily counteracted by exhibiting its 
consequences. A slender waist is regarded as graceful, and so long as it 
is so regarded, it will be sought even at the expense of health. If a taste BONES OF THE TRUNK. 
41 
III. Bones of the Pelvis. 
The Pelvis is composed of the ossa innominata, the sa- 
crum, aud the coccyx. 
for more active employment could be cultivated, it would control this 
fashion, by rendering so much compression unendurable. Let habits of 
productive industry be formed by those to whom the avails of it would 
not be a motive. Such habits are important, not simply from the possi- 
bility that they may come into requisition by reverses of fortune, but 
specially so, in consequence of the influence which they would have in 
giving a proper development to the physical as well as mental and moral 
system. But if these are to be discarded, the only substitute for them, so 
far as a healthy physical development is concerned, is to require a large 
amount of active out-of-door life, such as travelling, walking long distances 
in the open air, riding on horseback, etc. Such active habits, whether 
they be those of amusement or of productive industry, require a large 
supply of air in respiration, and it will be natural and almost necessary 
to adapt the dress to this demand. 
Fig. 28. 
Kg. 29. 
A fully developed Chest, 
Chest contracted by compression. 
Still, since this habit of compressing fin thonx prevails to such an 
extent, it is proper to remark that other habits of cultivated society, how- 42 
BONES OF THE TRUNK. 
41. The sacrum and coccyx have before been re- 
ferred to as forming the lower part of the spine. They 
also constitute the back part of the pelvis (2 and 3, Fig. 30). 
Tig. 30. 
The Pelvis. 1 The ilium. 2 The sacrum. 3 The coccyx. 
4 The acetabulum. 
ever objectionable they may be in themselves, are, to some extent, com- 
pensatory of the evils of tight dressing. The capacity of the thorax— 
that is, the amount of respiration—which would be necessary in one state 
of society, would be altogether unnecessary in another. The habits of 
women in the most refined society of the age when the Venus de Medici 
was the beau ideal of female form, were such as to require a much fuller 
development of the thorax than would be required by the habits prevail- 
ing in the corresponding ranks of society at the present time. A lady, 
whose severest employments are embroidery and romance reading, re- 
quires but little air in respiration, and therefore only a small chest. 
Also, the different pursuits and conditions of men render the amount 
of air required very different. An insufficient amount of clothing, expo- 
sure to severe and long continued cold, and the most active physical 
labor, require of the sailor, of the hunter, of the backwoodsman, and even 
of the farmer and the laborer in many mechanical employments, such a 
development of the thorax, and such an amount of air in respiration, as 
would be not only unnecessary but hurtful to the laborer in the more 
sedentary mechanical employments, to the student, the clerk, the merchant, 
and the professional man. 
41. Why are the sacrum and coccyx mentioned in this connection ? BONES OF THE UPPER EXTREMITIES. 
43 
42. The ossa innominata (bones without a name, 
Fig. 30), are two irregularly-shaped bones, proceeding from 
the sacrum, one on each side and meeting in front. Each 
bone, from having been in the early stages of ossification 
in three pieces, is generally spoken of as three bones, the 
ilium, which is the upper part (1); the ischium, which is 
the lower part; and the pubis, which is the front part. 
43. The pelvis furnishes the vertical support for the 
abdominal viscera. It also gives support to the spine, and 
hence to the head and trunk. The pelvis furnishes the 
means of attaching the lower extremities. For this pur- 
pose, it contains a large socket on each side (4, 4, Fig. 30), 
called the acetabulum. The ilium, ischium, and pubis, all 
unite at the centre of this socket, and contribute to form it. 
Section IV.—Bones of the Upper Extremities. 
They are the scapula, clavicle, 
bones of the arm, forearm, and 
hand. 
rig. 31. 
44. The scapula (Fig. 31) is a 
broad, thin bone, of a triangular 
shape, and lies imbedded in the 
muscles of the back. Near its outer 
angle the bone becomes thick and 
terminates in a slightly concave 
surface (1, 1), called the glenoid 
cavity. The coracoid process (3) 
rises from the neck of this cavity 
and projects over it in front. The 
The Scapula. 1,1 The glenoid 
cavity. 2 The coracoid pro- 
cess. 3 The spine of the scap- 
uia. 4 The acromion. 
42. Describe the ossa innominata. Why have the three parts distinct names ? 
What are the three parts, and how are they situated ? 
43. What are the three uses of the pelvis ? How does it furnish the means of 
attaching the lower extremities ? 
Section IV’.—What are the bones of the upper extremities ? 
44. Describe the scapula : the glenoid cavity ; the two processes of the scapula. 
How is the socket for the shoulder joiiu formed ? 44 
BOXES OF THE UPPER EXTREMITIES. 
high ridge of bone (3) on the back of the scapula, is called 
the spine of the scapula. It terminates in a process (4), 
I called the acromion of 
the shoulder), which reaches 
beyond the glenoid cavity on 
the back side. The socket for 
the shoulder joint, is formed 
by the glenoid cavity, raised 
at its edges by cartilage, and protected by the coracoid pro- 
cess and the acromion. 
Fig. 32. 
The Clavicle, e, its articulation with, 
the sternum, d, its articulation with 
the shoulder. 
Fig. 33. 
45. The clavicle (Fig. 32, 
seen also in Fig. 25) extends from 
the upper extremity of the ster- 
num, to the acromion of the scap- 
ula. Its use is to brace the scapula 
hack, and prevent the shoulders 
from falling in toward each other, 
so as to restrict the motions of 
the arms.15 
Kg 34 
46. The humerus (Fig. 33) 
extends from the shoulder to the 
elbow. The upper extremity is 
received into the glenoid cavity to 
form the shoulder joint. The hone 
is nearly cylindrical except at the 
lower extremity, where it is flat- 
tened ; and the corners of it (5 and 
6), are the external and internal 
condyles. Between these condyles 
on the front side is a depression, 
called the lesser sigmoid cavity, 
and on the hack side, directly 
opposite, is a similar depression 
called the greater sigmoid cavity. 
ThcHnmerns. 1 
The Shaft. 2 
The head fit- 
ted to the glen- 
oid cavity. 5, 6 
External and 
internal con- 
dyles. 
The Ulna. a 
The sigmoid 
cavity, b The 
coronoid pro- 
cess. e The 
olecranon. BONES OE THE UPPER EXTREMITIES. 
45 
47. The bones of the fore arm are the ulna (Fig. 34), 
and the radius. They reach from the elbow to the wrist, 
and are nearly parallel. The 
upper extremity of the ulna, the 
point of the elbow (e) is the 
olecranon. A little lower on 
the front side of the ulna (J) 
is the coronoid process, and 
the sigmoid cavity of the ulna 
(a) is between these processes. 
This cavity receives the lower 
extremity of the humerus to 
form the elbow joint. When 
the elbow is bent to a sharp 
angle, the coronoid process falls 
into the lesser sigmoid cavity of 
the humerus and prevents any 
further flexion. In like manner, 
when the arm is straightened, 
the olecranon fits into the great- 
er sigmoid cavity and checks the 
motion in that direction. 
The radius (Fig. 35), at its 
upper extremity, has a small 
protuberance (3, Fig. 36), which 
Fig. 35. 
Tic:. 36. 
Bones of the fore arm. 
1 The ulna. 2 The 
radius. 3,4 The con- 
dyles, which, with 
the corresponding 
cavities, form the 
joint for the rolling 
motion of the hand. 
The Radius. 
16 The clavicle is fully developed only in the human species, though it 
is found in a rudimentary state in such other animals as the cat, squirrel, 
and monkey, which use the fore feet, to some extent, as hands. In those 
animals which use the anterior extremities only as organs of locomotion, 
motion is required in only one direction. These extremities are in such 
animals brought near together, and the clavicle is therefore entirely wanting. 
45. Describe the clavicle. What is its use ? 
46. Describe the humerus. Describe the condyles and cavities of its lower 
extremity. 
47. What are the bones of the fore arm ? How are they situated ? How is the 46 
BOXES OE THE UPPER EXTREMITIES. 
is fitted to a slight depression in the ulna. In the same 
way the ulna is attached at its lower extremity (4) to the 
radius. The ulna, in consequence of the hinge joint at the 
elbow, can have no rolling motion, but the radius in conse- 
quence of this double joint (3 and 4) is capable of per- 
forming nearly half of a revo- 
lution, and as the wrist is not 
articulated with the ulna but 
with the radius, the rolling 
motion of the radius carries 
the hand with it. The mo- 
tions of pronation and supi- 
nation of the hand, depend 
therefore upon this double ar- 
ticulation of the radius and 
ulna.15 
Eig. 37. 
48. The bones of the 
Hand. The wrist is formed 
of eight carpal bones (1, 1, 
Fig. 37); the hand by five 
metacarpal bones (2, 2), and 
the thumb and fingers by the 
five bones in each of the first 
The Hand. 1,1 The carpal bones. 2, 
2 The metacarpal bones. 3, 3. 4, 4. 
6, 5 Phalanges. 
16 The extent of motion of this kind of which any person’s hand is sus- 
ceptible is easily determined by trial. Expose the fore arm, and hold the 
elbow so that there shall be no motion of the humerus, then see how far 
the hand can be made to rotate. In young persons it will often be three 
quarters of a revolution; but the utmost possible amount should not often 
be attempted. The movement of the radius will be distinctly seen, though 
enveloped in muscle and integument. 
sigmoid cavity of the ulna formed, and what is its use ? What are the processes 
above and below this cavity? What limits the motions of the elbow joint for- 
ward ? How are they limited backward ? Describe the articulations of the radius 
and ulna. What is the object of this mode of articulation ? Why cannot the roll- 
ing motion of the hand be performed by the elbow joint ? 
48. Describe the bones of the hand. BONES OF THE LOWER EXTREMITIES. 
47 
and second phalanxes (3, 3 and 4, 4), and four bones (5, 5), 
in the third phalanx. 
49. In the structure and use of the superior extremities, 
there is a broad anatomical distinction between man and 
the inferior animals. In all other animals, they are designed 
to be used, more or less, as organs of support and locomo- 
tion, and this use renders them loss fitted for the special 
uses to which they are appropriated in man, that is, as 
organs of touch and prehension. 
Their peculiar adaptation to these purposes consists in 
their length, in their slender form, in the freedom of mo- 
tion of which they are capable at all the joints, particularly 
those of the shoulders, in the extent of pronation and 
supination of the hand, in the degree of separateness given 
to the fingers, in the position of the thumb, which is 
directly opposed to the fingers, in the muscular power of 
the thumb, which nearly equals that of all the fingers, and 
in the great delicacy of the sense of feeling in the hand, 
and particularly at the ends of the fingers. 
Section V.—Bones of the Lower Extremities. 
These are the femur, the tibia, the fibula, the patella, 
and the bones of the foot. 
50. The femur (Fig. 38) has, at its upper extremity, 
three well marked prominences. The first is the highest 
49. What distinction is mentioned between the anatomy of man and the infe- 
rior animals? WThat are the uses to which the upper extremities, in man, are 
principally subservient ? To what uses are the corresponding organs put in other 
animals? Why must they be less perfect, than in man as organs of prehension 
and touch ? They are adapted to these purposes in man by peculiarities in eight 
respects ; what are they ? 
Section I".—What are the bones of the lower extremities? 
60. Describe the femur. 48 
BONES OE THE LOWER EXTREMITIES. 
part of the shaft of the hone (4), and is called the trochan- 
ter major. The next is the head of the femur (3). It sets 
Fig. 38. 
off from the axis of the 
femur about three inches 
on a neck of hone, and 
terminates by a spherical 
surface which is received 
into the acetabulum to 
form the hip joint The 
third eminence (2) is the 
trochanter minor, situ- 
ated on the interior side 
of the femur below the 
neck. On the posterior 
face of this hone for about 
two thirds of its length, 
is a rough ridge called the 
linea aspera. The infe- 
rior extremity of the fe- 
mur presents a large ar- 
ticulating surface for the 
knee joint. This surface 
(7) is divided behind by 
a deep groove into two 
portions, called the exter- 
nal and internal condyles 
(5 and 6). 
Fig. 39. 
1 The Tibia. 5 The 
Fibula. 2, 3 The 
external and in- 
ternal malleolus. 
4. 7 Articulating 
surfaces. 
The Femur. 1 The 
shaft. 2 The tro- 
chanter minor. 3 
The head of the fe- 
mur. 4 The trochan- 
ter major. 5, fi Ex- 
ternal and internal 
condyles. 7 The ar- 
ticulating surface for 
the knee joint. 
51. The tibia and fibula (Fig. 39) 
are two parallel bones reaching from the 
knee to the ankle. The largest bone (1) 
is the tibia. Its upper extremity presents 
a large surface for the articulation at the knee. The lower 
extremity articulates with the astragalus (the central bone 
51. Describe the tibia. How is the ankle joint protected? BOXES OF THE LOWER EXTREMITIES. 
49 
of the ankle) to form the ankle joint; and a process of the 
tibia (3), called the internal malleolus, extends down the side 
of the astragalus to protect the joint. 
52. The fibula (5) articulates with the head of the tibia 
just below the knee joint, extends on the outside of the leg 
to the ankle joint, and terminates in the external malleolus 
(2) at the side of the astragalus. 
53. The patella is a flat circular bone about two inches 
in diameter, situated in 
front of the knee joint 
(Fig. 40). As the knee 
joint is one of the most 
exposed in the system, this 
bone is placed over it to 
strengthen it. An ordinary 
tendon passing over this 
joint would also be liable 
to frequent injury, and we 
may regard the patella as 
only an ossified portion of 
the tendon which transmits 
over the joint the muscular 
power by which the knee 
is straightened. 
54. Bones of the Foot 
The ankle is formed by 
seven tarsal bones {g, d. 
Fig. 41), the foot, by five 
metatarsal bones (a), and 
the toes, by five bones in 
each of the first and second phalanges (5, and c), and four 
bones (m), in the last phalanx. 
The bones of the Lower Extremities. 
52. Describe the fibula. 
53. Describe the patella. What are its uses? 
64. What are the bones of the foot? 50 
BONES OF THE LOWER EXTREMITIES. 
55. Since the body, in man, is to be supported on two 
extremities, instead of four, as in other animals, it is neces- 
sary that the foot should have certain peculiarities, fitting 
Fig 41. 
Bones of the foot. a. The metacarpal honest, b.c, m. The phalanges. /, The 
astragalus, g, The os calcis. 
it for this office. These peculiarities are its length, the 
projection of the heel backward, and its articulation at 
right angles to the leg. 
Its adaptation to the required motions, those of walking, 
leaping, and running, consist principally in the great power 
of the muscle which is attached to the extremity of the 
heel (the os calcis, 3, Fig. 42), the length of this bone as a 
Fig. 42 
A vertical section of the Font, lengthwise. 1 The tibia. 2 The astragalus. * 
The os calcis. with the tendon of the muscle attached. 4, 5 Bones of the foot, 
fi A metatarsal bone. 7, 8 Phalanges. In this figure the arched form of the loot 
is well shown. 
55. What is the first office of the foot? What peculiarities fit It for this pur- 
pose? What is the second, and how Is It fitted for it? What is the third use of PARTS OF WHICH THE JOINTS ARE COMPOSED. 
51 
lever, and the power of varying very much the angle made 
by the leg and foot. 
The motions of the body, would be injurious to the brain 
and vital organs, if there were no provision for absorbing 
them. Such concussions we experience by stepping only 
a few inches lower than we expect to, when walking in the 
dark. The principal means of deadening these shocks 
consist in the construction of the foot. In these motions, 
either the toe or heel, first receives the weight of the body, 
and the concussion is partially absorbed, before the other 
end of the foot is brought down. The arch of the foot, 
directly over which the ankle joint is placed, is then de- 
pressed. If too much of the concussion still remains, the 
knee and hip joints are then gradually bent, in order to 
receive it. 
Section /.—Parts of which the Joints are composed. 
CHAPTER II.—OF THE ARTICULATIONS. 
56. A joint is formed by the con- 
tact of two articular faces of bone, 
together with several appendages for 
guarding it against dislocation, and 
for securing freedom of motion. 
57. If the surfaces of bone were in 
direct contact, the requisite motions 
would rapidly wear them, and de- 
stroy the joint. To obviate this, a 
layer of cartilage (2, 2, Fig. 43) covers 
every articular surface. Thus, in- 
stead of bone, there are brought to- 
gether two smooth surfaces of an 
elastic substance between which there 
is scarcely any friction. 
pig. 43 
1,1 Two bones connected by 
a joint. 2, 2 The cartilages 
by which the ends are cov- 
ered. The synovial mem- 
brane, represented by the 
dotted lines, covers the 
cartilage, and extends back 
to 3. 3; then follows the 
capsule, which lies outside 
of the dotted line, and is 
not here represented. 
the foot ? What are the means by which the foot absorbs the concussion produced 
by the motions of the body ? What further provision exists for absorbing them ? 52 
PARTS OF WHICH THE JOINTS ARE COMPOSED. 
A cartilage which covers a convex articular surface is 
thickest in the middle (Fig. 44), and that which covers a 
concave surface is thickest around the edges. This ele- 
vated rim of cartilage in some of the joints, as that of the 
Fig. 44. 
A C The Cartilages of a joint, varying in thickness according to position. 
shoulder, constitutes the most important part of the sock- 
ets, so that cartilages become, to a considerable extent, a 
protection against dislocation. 
There is also in several of the joints, as in the knee, a 
separate, intervening cartilage, so that each joint in which 
it is found really consists of two joints. By this means the 
amount of motion over each articular surface is diminished 
one half. 
58. Every joint is inclosed in a capsule which binds the 
bones together, and prevents the adjacent parts from fall- 
ing in, and being caught between the bones as they move 
upon each other. This capsule is a continuation of the 
periosteum, which, instead of closing around the end of the 
bone, becomes detached from it where the articular surface 
commences, and, passing over the joint, attaches itself to 
the next bone. The joint is therefore contained within a 
sac impervious to air. 
Chapter IS. Section I,—56. Of what does a joint consist? 
57. Why are not the articular surfaces of bone brought directly together? 
With what are the articular surfaces covered ? How does the thifkness vary ? 
How do some of the cartilages tend to strengthen the joints ? What is the use of 
the separate cartilage in certain joints ? 
58. What is the use of the capsule ? How is it formed ? How, apart from its 
strength, as a means of tying the bones together, does it protect the joint ? PARTS OF WHICH THE JOINTS ARE COMPOSED. 
53 
The close fit of the articular surfaces which form a joint 
is among the prominent means of protection. The sur- 
faces adhere by atmospheric pressure with a force equal to 
sixteen pounds to the square inch of surface. It is the 
same principle which the dentist employs in securing to 
the roof of the mouth the plate to which artificial teeth are 
attached. The plate can be loosened, however, by depress- 
ing one side so as to admit the air. The joint is more fully 
protected, because the inclosing capsule entirely excludes 
the air. 
59. In addition to the capsular 
support of the joints, they are sup- 
plied with numerous ligaments as 
protection against dislocation. 
They are sometimes only a thick- 
ened and strengthened state of the 
capsules at exposed points. Other 
ligaments are quite separate from 
the capsule. Fig. 45 represents the 
inside of the hand with the mus- 
cles dissected off, and will give a 
good general idea of the abundance 
of ligaments with which the joints 
are furnished, and the amount of 
protection which they give. 
Fig. 45. 
The ligaments are severally 
adapted to the amount of motion 
which the joints require. Thus 
the ligaments of the shoulder joint 
are, within certain limits, as elastic 
as India-rubber. Otherwise the 
joint would be comparatively useless. But the ligaments 
which bind the square bones of the wrist or foot together 
Represents the ligaments which 
pass from one hone to an- 
other in the hand. Also the 
ligament which connects the 
bones of the fore arm. 
59. What protection have the joints in addition to the capsules ? Are the liga- 54 
PARTS OF WHICH THE JOINTS ARE COMPOSED. 
have scarcely any elasticity. If they had they would answer 
no good purpose in those places. 
Again, there is a striking adaptation in the amount and 
arrangement of the ligaments to the degree of danger to 
which a joint is exposed. When a joint is otherwise weak, 
especially if it is an important one, greater care is taken 
to protect it by ligaments. In the knee joint, for instance, 
if the bones were larger the joint would be stronger, but 
the limb would be more cumbrous. With the size which 
the bones of the knee have, it might be asked, how its 
strength may be made the greatest, while yet the free- 
dom of motion is not interfered with. The question is 
solved in the construction of this joint. Besides a lib- 
eral supply of ligaments passing across the joint from 
bone to bone, outside of the capsule, there are within the 
capsule two ligaments, originating in the deep groove 
which separates the external and internal condyles,17 cross- 
ing each other like the letter x (and hence called cru- 
cial ligaments), and attached to the head of the tibia 
(/g, Fig. 46). The advantage of this arrangement is that 
the protection is almost in the centre of the joint, and 
1T We have here an instance, not uncommon in the anatomy of the 
body, of several ends attained by the same contrivance. This groove 
might, at first, appear to be left only to make the bone lighter, and yet 
give the requisite enlargement of the extremity of the bone, for the pur- 
pose of forming the joint. We now see that it answers another purpose, 
by furnishing the means of attaching, in the most favorable position, those 
ligaments upon which depends the principal security of the most exposed 
joint in the system. As this joint is the most exposed one in the system, 
so the blood vessels and nerves which pass it would be especially exposed 
to be injured, but for this groove, which furnishes them a passage along the 
least exposed side of the joints, deep below the surface, and protected from 
injury by the condyles which rise up on both sides. 
ments separate from the capsules ? How are the ligaments adapted by their elas- 
ticity to the proper motion of the joints? What other adaptations have they? 
Explain this adaptation in case of the crucial ligament. Of the round ligament. PARTS OF WHICH THE JOINTS ARE COMPOSED. 
55 
also that the direction of the ligaments is such, that any 
force tending to cause dislocation, must be exerted in a 
direction almost lengthwise of one or other of these liga- 
ments. Their position is therefore such as to make thent 
operate to the greatest possible advantage. 
Fig. 46. 
Fig. 47. 
The back side of the 
Knee Joint, f g 
The crucial liga- 
ments by which the 
joint is protected in 
the centre. 
The Hip Joint, b r, The round ligament, 
c l The capsular ligament. 
Another instance of a similar kind is the round liga- 
ment of the hip joint (r l. Fig. 47), which has very great 
strength, and passes directly from the centre of the head 
of the femur to the centre of the acetabulum. It is suffi- 
ciently elastic to allow of the requisite motion, but not of 
motion to such extent as to render dislocation possible 
without breaking the ligament. 
In a few cases there are ligaments passing from bone to 
bone, to give greater support to the parts where there is 
no proper joint. Of this kind are the ligaments between 
the tibia and fibula, and that between the radius and 
ulna (Fig. 45). 
In what instances are ligaments employed to confine bones within proper limits 
where there are no joints ? What other use is made of ligaments ? There is another class of ligaments which have an en- 
tirely different object. They occur where a tendon is to 
take a different direc- 
tion from that of the 
muscle from which it 
comes; in the instep of 
the foot, for example 
(Fig. 48), where the 
symmetry of the foot 
would he entirely de- 
stroyed if the tendon 
which goes to the toes, 
instead of being tied 
down into the angle, 
were allowed to pass di- 
rectly from the muscle 
to the points of inser- 
tion. Its object there- 
fore is to change the 
direction of muscular 
motion. 
56 
PARTS OP WHICH THE JOIKTS ARE COMPOSED. 
Fig. 48. 
The direction of muscular motion changed 
by ligaments. 
60. The whole internal surface of the joint, that is, of 
both cartilages and the capsule, is lined with the synovial 
membrane (represented by the dotted line in Fig. 43). 
There are also in several parts of the body tubular sheaths 
for the transmission of tendons, and where the amount of 
motion is such as to require that the surfaces should be 
covered with synovial membrane. 
This membrane secretes a glairy and very perfectly lu- 
bricating fluid, the synovia, the office of which is the 
same as that of lubricating substances used in all kinds of 
60. With what are the surfaces of the joints lined ? What is the object of this 
membrane ? What is the office of the synovia ? What advantages have the joints 
over other machinery in this respect ? PARTICULAR JOINTS. 
57 
machinery, to diminish the friction of solids moving upon 
each other. The joints have, however, these advantages 
over other machinery, that the synovia is the most perfect 
lubricating substance known, that it is supplied over the 
whole surface requiring lubrication, that the quantity is 
exactly proportioned to the demand, since the amount 
secreted depends upon the amount of motion of the joint, 
that it is not supplied at intervals but constantly, and that 
the old is absorbed as the new is secreted. 
61. The joints are either movable or immovable. We 
have examples of the immovable joints in the sutures of 
the head and face, and in the articulations of the teeth 
with the alveolar processes. 
Section II.—Particular Joints. 
The movable joints are of four kinds. 
62. First, those which admit of motion only by the com- 
pression of interarticular cartilage. The articulations of 
the vertebrae, with the exception of the two highest, are of 
this kind. Each cartilage is firmly fixed to the two verte- 
brae next above and below it. Instead of two cartilages, 
as the other joints have, each joint contains but one, but 
this is of much greater thickness, so that it will admit of 
compression enough to produce all the motion required. 
These joints are not supplied with synovial membrane, as 
there is no motion of surfaces upon each other. The 
articulation of the bones of the pubis in front is of this 
kind, though the cartilage is not thick enough to admit 
Section II.—61. What are the two kinds of joints ? What are examples of 
the immovable joints ? How many kinds of movable joints ? 
62. What is the first kind ? Describe the joints of the spine. Why have they 
no synovial membrane ? What other joints belong to this class ? 58 
PARTICULAR JOINTS. 
of much motion. The articulations between the ilium 
and sacrum, and between the tibia and fibula resemble 
those of the vertebras, but each surface of bone has a sep- 
arate cartilage and is lined with synovial membrane. 
63. Secondly, those which admit of motion in only one 
direction. The articulation of the occiput and atlas allows 
only the vertical motion, that of the atlas and axis only 
the horizontal motion, and upon these two joints most of 
the motions of the head are performed, though the other 
joints of the neck admit of considerable motion. The 
elbow, knee, and ankle joints are the most perfect exam- 
ples of this kind. The articulations of the phalangial 
bones with each other also belong to this class. They are 
called hinge joints, and though limited to one kind of 
motion, the motion is yet very free and extends through a 
large arc. In the elbow joint, as before stated, the motion 
is limited both ways by processes of the ulna, but the range 
of motion of the other hinge joints is determined more by 
the ligaments than by the form of the bones. 
64. Thirdly, the condyloid articulations. The articula- 
tion of the lower jaw with the temporal bone belongs to 
this class. The usual action of this joint is such as to give 
a vertical motion to the jaw. But the cavity in the tem- 
poral bone, which forms the socket, is larger than the con- 
dyle of the lower maxillary bone, so that a slight lateral 
(the grinding) motion is allowed, and also some motion 
backward and forward. The articulation of the clavicle 
with the scapula and with the sternum, those of the ribs 
63. What is the second kind ? Describe the first and second joints of the spine, 
and their object. What are the remaining joints of this kind ? By what general 
name are they designated ? How is their motion limited 1 
64. What is the third kind of joints ? Describe the articulation of the lower 
jaw. Name the other joints of this class. What is the peculiarity of the articu- 
lation of the radius and ulna ? Why is the joint between the wrist and thumb 
classed with the condyloid joints ? ARTICULAR JOINTS. 
59 
with the vertebrae and the transverse processes, ana those 
of the phalanges with the metacarpal and metatarsal bones 
are of this kind. The articulations of the carpal bones 
with each other, and with the metacarpal, also those of the 
tarsal with each other and with the metatarsal, belong to 
this class, though the motions in these joints are extremely 
limited. The articulation of the radius and ulna is com- 
posed of two condyloid joints, one at each end, by which 
the rotary motion of the hand is provided for. The joint 
between the thumb and the wrist, though of a peculiar 
construction, is in its motions very much like the con- 
dyloid joints. 
65. Fourthly, those articulations which admit of free 
motion in all directions These are denominated ball and 
socket joints. There are but three joints of this kind In 
the wrist joint the bones of the carpus are so arranged as 
to form a spherical surface which is fitted to a shallow 
socket on the end of the radius. This is a weak joint, not 
fitted for the support of much weight, but for that freedom 
of motion by which the hand is adapted to be an organ of 
prehension. In the shoulder joint the ball of the humerus 
is received into the glenoid cavity, the edges of which are 
so raised by cartilage as to form a perfect socket. To form 
the hip joint, the head of the femur is received into the 
acetabulum. This is the most perfect ball and socket in 
the system, both by the shape of the bones which go to 
form it, and by the appendages of cartilage which raise the 
rim of the socket. 
65. What is the fourth kind of joints ? What ar they called? What joints 
are included in this division ? Describe each joint. GENERAL DESCRIPTION OF THE MUSCLES. 
CHAPTER III.—OF THE MUSCLES. 
Section I.—General description of the Muscles. 
68. The muscles are either voluntary, involuntary, or 
mixed. The heart and stomach are instances of involun- 
tary muscles, that is, muscles which contract and relax 
under a stimulus which is independent of the will. Those 
muscles upon which respiration depends are both volun- 
tary and involuntary, that is, they contract and relax with 
regularity when the attention is withdrawn from them,.but 
they can still be controlled by the will.18 Those muscles 
upon which the motions of walking, eating, winking, 
writing, etc., depend, and which, in a state of health, con- 
tract and relax only in obedience to the will, are called 
voluntary muscles. 
67. Those muscles which are partially or wholly con- 
J3 It is not improbable that these mixed muscles (being supplied with 
voluntary and involuntary nerves) may be constantly stimulated by the 
involuntary nerves, and uniformly obey them when there is no opposing 
influence, but that the power of the voluntary nerves is superior when the 
will is active, and controls their motions temporarily. Unless these mus- 
cles were involuntary, life could be continued only so long as we could re- 
tain the waking state, and direct our attention to the process of respira- 
tion. It is also very important that these muscles should be voluntary, so 
that we may control the degree of force with which respiration is effected, 
and also control the length of each act of respiration; otherwise, we could 
have no control over the voice. We might be able to articulate while the 
air was passing out of the lungs, but we would be unable to vary the com- 
pass of the voice at all, and if the act of expiration should terminate while 
we were pronouncing a word, we should be unable to complete it till the 
next expiration. 
Chapter III. Section I.—66. Into what classes are the muscles divided? 
Give examples of each class. 
67. What do the voluntary and mixed muscles constitute ? How are they sit- 
uated ? What effect have they upon the general form of the body ? GENERAL DESCRIPTION OF THE MUSCLES. 
61 
trolled by the will constitute the lean meat of animals. 
They lie upon the bones, filling the depressions, and giving 
the general fullness and roundness of contour which belong 
to the different parts of the body. 
68. That end of the muscle which is not movable is 
called the origin. The point where the power is to be 
exerted is the insertion. This distinction, however, does 
not always hold, because in a few muscles each extremity 
is capable of becoming alternately the fixed and movable 
point. The fleshy part (the belli/ of the muscle) consists 
Fig. 49. 
A film of Cellular Membrane. 
of ultimate fibres, too minute to be well exhibited except 
by a glass of high magnifying power. Several of these 
fibres are collected together into a bundle (or fasciculus),19 
and inclosed in a sheath of cellular substance.20 A muscle 
19 In a piece of beef which has been cookei till it is very tender, the fas- 
ciculi of a muscle, inclosed in a very attenuated membrane, are well ex- 
hibited and easily separated. 
,J0 The cellular tissue consists of membrane of extreme tenuity (Fig. 49;, 
and pervades all parts of the system. The membrane stripped from the 
leaf of fat taken from a fattened animal, consists of several thicknesses of 
cellular tissue. The loose, bladder-like membrane, by which the skin of 
animals adheres to the muscular parts below, is cellular membrane. It 
68. What part of the muscle is called the origin ? What the insertion ? Why 
cannot the distinction always be made ? Describe the fleshy part of the muscle. 62 
consists of a collection of these fasciculi inclosed in another 
firmer sheath of cellular substance. 
GENERAL DESCRIPTION OF THE MUSCLES. 
69. At the extremities of the muscle the cellular sheaths 
which inclose the several fasciculi, and that which incloses 
the whole muscle, becoming free from muscular fibres, are 
condensed into a firm, inelastic tendon. When the muscles 
can conveniently be situated near the place where the 
power is to he exerted, the tendons are very short, and in 
many cases there is no distinct tendon formed. Otherwise 
tendons, often of considerable length, are employed.21 
forms a loose network which pervades very generally the other tissues Oi 
the body. It exists in the bones. It is this membrane inta the cells of 
which adipose matter is deposited to form the fat meat of animals. It is 
this membrane which incloses, with a sheath so thin as to be scarcely visi- 
ble, the fasciculi of ultimate muscular fibre. It is the same membrane 
which, in a condensed state, forms at one time the tough leathery sheaths 
(fasciae) by which the whole of a muscle, or several muscles, are inclosed, 
and, at another time, the tendons of the muscles or the ligaments of the 
joints. 
‘•il A correct idea of the use and action of tendons may be obtained by 
examining the leg of a fowl. The tendons are the small white cords 
which are prolongations of the muscles situated in the thigh (“ drum-stick”). 
By pulling the cords on one side the parts of the claw contract; by pulling 
those on the other side, the claw opens. 
We often find a highly artificial arrangement of tendons, and one which 
as fully proves an intelligent contriver as any complicated arrangement 
in a work of human skill. Thus the muscles are often at a distance from 
the place where the power is to be exerted, and the power is transmitted 
by tendons of the exact length necessary to effect the motions required. 
When a muscle is in the way of a tendon of another muscle, a slit is found 
in the first muscle through which the tendon of the other passes. A slit of 
this kind is made in the stylohyoid muscle for the tendon of the digastric 
muscle to pass. This last muscle has also another peculiarity, that the 
belly of it is divided into two parts which are connected by a tendon, and 
in order to change its direction, this tendon passes through a loop of cel- 
lular substance attached to the hyoid bone. The tendon (a, Fig. 50} which 
69. How are tendons formed ? In what cases are the muscles without tendons ? 
Then what is the use of tendons 1 GENERAL DESCRIPTION OF THE MUSCLES. 
63 
70. The muscles, though all composed of bundles of fas- 
ciculi, are yet very different in form. In some the fascic- 
uli are all parallel with the general direction of the muscle, 
as in Fig. 51, and it becomes spindle-shaped. Sometimes 
they diverge from a point and the muscle is fan-shaped, 
Fig. 51. 
Fig. 52. 
Fig. 53. 
Fig. 54. 
A spindle-shaped 
Muscle. 
A radiated 
Muscle. 
Apenniform 
Muscle. • 
A sphincter 
Muscle. 
Fig. 53. Sometimes the fasciculi are oblique to the gen- 
eral direction of the muscle, and are arranged along one 
bends the last joint of the finger, 
lies under the tendon which goes 
to the second joint; and in order to 
let this lower tendon pass the sec- 
ond joint, the upper tendon (b) is 
divided and attached at two points, 
and the lower tendon passes between 
the two branches. The muscular 
Fig. 50. 
a The ligament which passe? under the 
bifurcated ligament b, to go to the last 
joint of the finger. 
power exerted on the top of the foot first has its direction changed by pass- 
ing under the transverse ligaments of the ankle. The muscular power ex- 
erted on the bottom of the foot first has its direction changed by the ten- 
dons passing around a groove in the heel similar to the groove in the 
wheel of a pulley. The trochlearis muscle gives a motion to the eyeball 
directly opposite to that which would be produced if it were inserted by a 
straight tendon into the top of the ball. This reverse motion is produced 
by the tendon passing through a ring in the angle of the bone above the inner 
corner of the eye, and then going back to be inserted into the top of the ball. 
70. Describe the several forms which the muscles are found to take. 64 
GENERAL DESCRIPTION OE THE MUSCLES. 
or both sides of a tendon, as in Fig. 53, and the muscle is 
said to be penniform. Still others are circular, and by 
contraction close the opening which they encircle, as the 
mouth, the eye. They are called orbicular or sphincter 
muscles, Fig. 54. 
71. The general principle in the arrangement of the 
muscles is, that they are as near as possible to the places 
where the motions are required. This is the case in the 
neck, head, and trunk. There is, however, a wide excep- 
tion to this law in the position of the muscles which move 
the extremities. Here, the rule is, that the muscles are 
placed as near the trunk as possible. The object is to give 
to the limbs lightness and adaptation to free and rapid 
motion. Hence the muscles which move the shoulder are 
on the body, those which move the elbow are on the arm, 
and those which move the wrist and fingers are on the fore- 
arm. The same general arrangement exists in reference to 
the lower extremities. So far as mechanical power is con- 
cerned, the situation of the muscle might be, at least in 
part, reversed. Those, for instance, which move the elbow 
joint might have been in the fore-arm, etc., but it is ob- 
vious that the hand would have been heavier and more un- 
wieldy. Certain very weak but quick motions are, however, 
performed by muscles which are situated in the hand and 
along the fingers. But these muscles are so small as not 
to add perceptibly to the weight of the hand. 
72. The three principal circumstances noticeable in ref- 
erence to muscular action are, First, rapidity of the 
71. What is the general law for the position of the muscles ? In what parts 
of the system does this arrangement prevail ? In what parts of the system does 
a different principle prevail, and what is it ? What is the object of it ? Are 
there any muscles situated on the hand and on the fingers ? What is the size of 
the muscles, and what kind of motions do they perform ? 
72. What muscles act without mechanical disadvantage? Is this generally 
the case ? Are the muscles best fitted to exert great force or to produce a wide 
range of motion ? How is force converted into motion f GENERAL DESCRIPTION OF THE MUSCLES. 
65 
motions produced. Some of the muscles, as the heart 
and the straight muscles of the abdomen may exert a power 
equal to the force with which they contract. But such is 
not the case generally, and particularly with those which 
move the limbs. The force with which they contract 
seems to be abundantly supplied in the system, but the 
constitution of the muscle is such, that an amount of con- 
traction equal to the range of motion required is impos- 
sible. There is, therefore, such a construction of the 
framework, and such a disposition of the muscles, that a 
large supply of muscular power, with a limited amount of 
muscular contraction, shall be converted into a wide range 
of motion. The muscles are said to act at a disadvantage, 
which is true so 
far as power is 
concerned, but it 
is simply an ex- 
change, a contriv- 
ance to relinquish 
power which the 
system can spare, 
in order to secure 
greater and quick- 
er motion which 
it needs.22 Thus, 
in Fig. 55, by a 
small amount of 
muscular contrac- 
tion, the hand is 
Fig. 55. 
1 The humerus. 2 The muscle by which the joint is 
straightened. 3 Its insertion. 4 The muscle by 
which the elbow is bent. 5 Its origin. 6 Its inser- 
tion, When the muscle 4 contracts by an amount 
represented by 7, 8, the amount of motion of the 
ball will be represented by 9, 11. There is a loss of 
power which is compensated by an increase of 
motion. 
22 The muscles which bend the elbow must exert a force equal to about 
twenty-five times that of the weight raised by the hand. It seems incred- 
ible that a force of more than half a ton should be exerted by the two 
small muscles which bend the arm ; yet such is the fact. Still, that power 
would be of little sendee to us if we could not change it, in part, into 66 
GENERAL DESCRIPTION OF THE MUSCLES. 
made to take successively the positions of 9, 10, and 11. 
If a muscle could have been attached at 13, and made to 
act in the direction of the arc, there would be no loss of 
power, but no muscle could perform the amount of con- 
traction which would be necessary.” 
73. Secondly, muscular antagonism. Every volun- 
tary motion of the body depends not only on the contrac- 
tion of one muscle or set of muscles, but also on the relax- 
ation of another muscle or set of muscles. Thus a perfect 
antagonism of muscular power exists throughout the sys- 
tem. When the motions performed are principally those 
of bending and straightening the joints, the two classes of 
muscles are called flexors and extensors. 
74. Thirdly, many of the motions are the combined re- 
sult of the contractions of several muscles. Each muscle 
has generally a distinct motion to perform, but there are 
cases in which the fasciculi of a muscle may contract in- 
dependently of each other, so that one muscle may per- 
velocity; that is, if we could not move a hand or a foot to a greater 
distance at once than the extent of the musculai contraction of even the 
longest muscle. 
23 But instead of seeking occasion to lengthen the muscles, and thus in- 
crease their range of motion, there seems to be an opposite tendency. 
Thus, the penniform muscle is an arrangement to increase the number of 
muscular fibres of which a muscle consists, and therefore to increase the 
power with which it contracts, but at the same time to shorten the fibres, 
and therefore diminish the amount of contraction. This arrangement is 
most conspicuous in the muscles which straighten the knee, where a great 
amount of contraction would be useless, but where great power is neces- 
sary to control a joint bearing the whole weight of the body, and where 
the muscles must act so disadvantageous^. 
73. What besides the muscular contraction is necessary to produce motion? 
WTiat relation of the muscular power is established in the system ? What are 
those muscles which bend the joints called ? Those which extend the joints ? 
74. How can the same muscle produce more than one kind of motion ? Do 
the motions often depend each upon several muscles ? Give instances. 67 
form several different motions. More frequently, however, 
a single motion is the result of contraction of several 
muscles. Thus the tones of voice depend upon the posi- 
tion and tension of cords which are controlled by several 
muscles. To produce these almost infinitely varied tones 
at pleasure, implies an instantaneous and perfect control 
of these muscles. So the rapid and perfectly accurate mo- 
tions of which artisans, musicians, and especially jugglers 
arc capable, depend upon controlling accurately a large 
number of muscles. 
GENERAL DESCRIPTION OF THE MUSCLES. 
75. This perfect control may be more easily acquired by 
some persons than others, but it is never gotten without 
effort. It is the result of training. We see this in the 
gradually increasing correctness of pronunciation which the 
child acquires, in the efforts which the student is obliged 
to make in getting the sounds of a foreign language, in 
learning to write, to knit, to play on a musical instrument, 
or in acquiring any other kind of motion which requires 
skill. 
We may lose, by disuse, the control which we have once 
had of muscles. Thus, if a bone be broken and we are 
obliged to relinquish the use of a limb wholly, even a 
few weeks are sufficient to place it quite beyond our con- 
trol. There are muscles properly situated for moving the 
ears, but they have been so long out of use, that it is 
hardly probable that the use of them could again be re- 
covered. 
76. The muscles produce their effects by contraction, 
diminution of length, and the power which they are Capa- 
ble of putting forth at once, if it could be made to centre 
75. How may this control be acquired ? Give instances. Give an instance in 
which this control is temporarily lost. Give an instance in which it seems to be 
lost beyond the power of recovery. 
7 6. How do the muscles produce the motions of the body ? What is the nature 
of the power which produces those changes f 68 
GENERAL DESCRIPTION OF THE MUSCLES. 
at one point would be equal to several tons’ weight; but 
of the nature of the muscular power we know nothing. 
That is, we do not know why a muscular fibre should be- 
come longer or shorter when we will it to be so. We only 
know that it does thus obey the will. It is one of the 
modes of the manifestation of the vital force, which will 
be considered in the chapter on respiration. All that we 
can do is to inquire into the conditions which seem to be 
essentially connected with this manifestation of force. 
77 In the first place, every exertion of muscular power 
is connected with a change in the substance of the 
muscle, some portion of it being decomposed and return- 
ing to a lifeless state. It is by this lifeless matter (meta- 
morphosed tissue), taken up by the blood in its circulation 
through the muscles, that the bright arterial red which 
it had when it left the heart, is changed to the dark color 
which it has when it comes back to the heart. 
The portion thus decomposed was held in a living state 
by a certain force. This force is set free when the por- 
tion becomes lifeless, and can then be made use of for 
mechanical results ; that is, to produce muscular contrac- 
tion. This return of living tissue to a lifeless state is 
not, therefore, accidental, but is necessary to muscular 
contraction, and is in exact proportion to the force of con- 
traction required. 
Hence it is that those employments are the most exhaust- 
ing which may not be very laborious but which incessantly 
exercise only one class of muscles. They require too great 
an amount of decomposition of this one class of muscles. 
The accountant who has done nothing for ten hours but 
sit and move the small muscles of the hand in writing, is 
77. How are the muscles affected by muscular contraction ? Why is this de- 
composition necessary ? What effect does this have upon the blood ? What 
employments are most exhausting, and why ? How is injury from such employ- 
ments to be guarded against ? GENERAL DESCRIPTION" OF THE MUSCLES. 
69 
more weary than the person who has labored hard in the 
field and brought all the muscles of the system by turns 
into vigorous exercise.34 Constant writing, sewing, turning 
a wheel, playing on a piano, or any employment which re- 
quires the use of one set of muscles exclusively, is weari- 
some and injurious, unless relieved by a large amount of 
rest and recreation. 
78. In the second place, the healthy action of the muscle 
requires an active circulation of the blood, for this 
constant destruction of muscular tissue must be connected 
with as constant renewal, and the blood is the means both 
of removing the decomposed muscle and supplying the 
material for the new. 
The energy with which the blood circulates is dependent 
in a great measure upon exercise of the whole system. Ex- 
ercise may operate in several ways to stimulate the circu- 
lation, but part of its effect is merely mechanical. Kelax- 
ation of the muscle allows the blood to flow into it, and 
contraction forces it out, and as there are contrivances in 
the blood-vessels to prevent its rushing backward, both con- 
traction and relaxation of the muscles tend to establish a 
more energetic circulation, and therefore a more complete 
repair of the waste occasioned by decomposition. 
79. The circulation of the blood in the muscles adapts 
itself in quantity to the amount of exertion which these 
24 It is noticed by teamsters that their horses weary much quicker when 
the road is uniformly level, and the effort required is not great, than on 
uneven roads, where the draught is often much greater. In the latter case 
different sets of muscles are exercised alternately. 
78. What is the second condition of muscular power? Why is this active 
circulation necessary ? Upon what does such a circulation depend ? How does 
exercise mechanically promote the circulation of the blood ? 
79. Upon what does the amount of circulation in the muscles depend ? Why 
does a person of active habits need more circulation in the muscles than a seden- 
tary person ? Why should a change from one mode of life to another be gradual ? 70 
GENERAL DESCRIPTION OF THE MUSCLES. 
muscles ordinarily make. Hence the muscles of a person 
who is accustomed to active employment receive a large 
amount of blood, and when he is prevented from putting 
forth his accustomed activity he becomes restive. For such 
a state of rest his amount of circulation is a diseased one. 
If, on the other hand, a person of sedentary habits attempts 
to perform in a day what would be a day’s labor for a work- 
ing man, he effects an amount of decomposition of muscu- 
lar tissue altogether disproportionate to the amount of 
renewal which the ordinary supply of blood can furnish 
in the same time, and the result is extreme exhaustion. 
The change from one mode of life to another can be safely 
made only by so slow degrees, that the power of adaptation 
in the system shall adjust the circulation in the muscles 
to the demands made upon them. 
80. This adaptation in the supply of blood to the amount 
of effort put forth, is however subject to two modifications. 
During the period of childhood and youth, the new mus- 
cular fibre is furnished in large quantity, but it is for the 
purpose of growth, and not because muscular effort and 
muscular decomposition had been great. In fact such per- 
sons often put forth and are able to put forth but little 
muscular power. It is also found that any class of muscles 
which is subjected to a great amount of exercise continu- 
ously, receive more muscular fibre than is decomposed, and 
they become increased in size; that is, the muscular fas- 
ciculi become more numerous. Instead, therefore, of re- 
quiring a muscle to perform extra labor continuously by a 
more rapid decomposition and renewal of the muscular 
fibre (which, beyond a certain degree, would generate dis- 
ease), the large supply of blood which exercise induces 
80. What is the first modification to which this relation of circulation and 
muscular effort is subject ? What becomes of the nutriment furnished by the 
circulation of young persons ? What is the second modification ? GENERAL DESCRIPTION OF THE MUSCLES. 
71 
goes to furnish a large number of fibres to perform the 
labor.*5 
81. Muscular action is dependent on nervous influ- 
ence. The nerves do not produce muscular power, for we 
may often be unable to exert this power while the nerves 
are uninjured. But they control (or the brain, through 
the nerves) the vital force which is employed in muscular 
contraction. Hence when the connection between a mus- 
cle and its nerve is interrupted there can be no muscular 
action. Hence also it is, that under excitement or a vig- 
orous effort of the will the muscular power may for a short 
time be so wonderfully increased. In a very short time, 
however, such energetic action of the muscles will produce 
exhaustion; and even moderate muscular action will at 
length bring on weariness. This weariness may arise from 
a failure of the vital force, or too great decomposition of 
the muscular tissue. In either case it is an indication 
from our constitution that the system requires rest.38 
16 Sculptors and painters study carefully the external changes which 
the muscles undergo from change in the mental states, from exercise, use, 
excitement, disease, etc. The best representations of Hercules (the em- 
bodiment, among the ancients, of their ideas of physical power) exhibit 
the muscles as very large, and those in the back and arms as specially 
large, firm, and well defined. 
46 It would be the natural order to follow this section by a description 
of the muscles individually. But these descriptions involve the use of tech- 
nical terms in great numbers, and a minute knowledge of osteology. These 
descriptions have therefore been introduced in an appendix, and can be 
referred to by those who have leisure and taste for more difficult study. 
81. What is the third condition of muscular power ? Why are not the nerves 
the source of power 1 What is Ihe office of the nerves in reference to the mus- 
cles? How does a high degree of excitement affect the strength of a person? 
What is the condition of the system indicated by weariness ? What is the instruc- 
tion which it conveys ? 72 
GENERAL QUESTIONS. 
Define Anatomy and Physiology. How many systems of organs are to be ex- 
amined ? Show in their order why these systems are necessary. 
GENERAL QUESTIONS ON THE PRECEDING CHAPTERS.” 
Chapter I.—Of what does this chapter treat? What are the subjects of the 
sections in this chapter ? 
Section 1.—What are the objects of the osseous system ? Give the process by 
which the osseous skeleton is formed. What is the composition 01 ordinary 
bone ? What division of the bones according to their form ? Explain the struc- 
ture of the bones. How do bones increase in length and diameter ? Describe the 
periosteum. 
Section 2.—Wrhat are the two divisions of the bones of the head ? What is the 
structure of the bones of the cranium ? Name the bones of the cranium, and give 
their position. What are the processes of the bones of the cranium, and where 
are they situated ? What is the form of the cranium ? WThat is a suture, and what 
ones are found in the cranium ? What are the purposes of the cranium? How is 
it fitted to accomplish each of these purposes ? Name the bones of the face and 
give their position. 
Section 3.—What division is made of the bones of the trunk? Of what does 
the spine consist? Describe a vertebra and its processes. Explain the differ- 
ences in the vertebrae in different parts of the spine. How are the bones of the 
vertebral column connected together ? Describe the intervertebral foramina and 
spinal canal. What are the objects of the spine? How is it fitted to effect each 
of these objects ? Describe the sternum. The ribs. The use of the thorax. The 
pelvis. Its use. 
37 A list of general questions has been appended to this part, at the close 
of Part 2 and Part 3, for the purposes of reviews and examination. The 
questions are designed to test the knowledge of the pupil, and others of a 
similar character will he easily added by the teacher. It is recommended 
that, as each section is completed, there be a review of it by some such 
general questions as have been given above. At the end of a chapter let it 
be reviewed by sections. Let Part 1 be reviewed by chapters, that is, let 
the object of each chapter be given; then each chapter by sections; then 
each section by topics; and thus the view of the subject which the learner 
acquires will be a connected one. 
This kind of general review should not, however, be allowed to take the 
place of more rigid reviews. Thoroughness can be acquired only by spe- 
cial attention in this respect. Pupils are often averse to reviews, because 
they are anxious to hasten the completion of any subject of study, and be- 
cause, in reviewing, the novelty of the subject is gone. The most profita- 
ble part of their study, however, is the reviewing. The text has been 
constructed with great brevity, in order to give sufficient opportunity to 
be thorough; but if time will not admit of completing the study, let it be 
thoroughly reviewed as far as it is studied. GENEKAL QUESTIONS. 
73 
Section 4.—What are the bones of the upper extremities ? For what uses are 
the bones of the upper extremities intended ? In what consists their adaptation 
to these uses ? 
Section 5.—What are the bones of the lower extremities ? What are the pur- 
poses designed to be accomplished by them ? What are the adaptations to each 
of these purposes ? 
Chapter II.—What is the subject of this chapter? -Section 1.—How is a joint 
formed? What are the four appendages of joints ? What are the four peculiari- 
ties of ligaments adapting them to the amount of motion and kind of danger ? 
For what other purposes are ligaments used ? In what respect is the synovia 
adapted to its uses ? Section 2.—What division is made of the joints ? How 
many kinds of movable joints ? Give instances of each kind. 
Chapter III.—What is the subject of this chapter? Section 1.—What division 
is made of the muscles ? What are the muscles here considered ? 'What are the 
forms of the muscles ? What is the general arrangement of the muscles ? What 
three principles prevail in reference to muscular motion ? How does practice 
affect our control of the muscular power ? What is the muscular power ? What 
three laws relating to the exercise of this power? What consequences follow 
from the first law? What affects the amount of circulation of blood in the mus- 
cles? Under what circumstances is the amount of circulation more than pro- 
portioned to the muscular power possessed? What is the third law? What is 
the physical cause of weariness, and what is its import ? PART II. 
THE NERVOUS SYSTEM. 
THE NERVOUS SYSTEM INCLUDES THE BRAIN, SPINAL CORD, 
NERVES, AND THE EXTERNAL SENSES. 
CHAPTER I.—OF THE BRAIN, SPINAL CORD, AND NERVES. 
Section I.—The Brain. 
I. The Enveloping Membranes of the Brain. 
82. There is a firm membrane called the dura mater, 
■which is closely attached to the interior surface of the 
cranium, and may be regarded as an internal periosteum. 
In several instances the membi’ane is not attached contin- 
uously to the bone, but leaves loose duplications {F, Fig. 
56), by which the 
brain is partitioned 
off into separate 
portions. One of 
these folds is the 
tentorium. It is a 
nearly horizontal 
membrane, arising 
from the ridge at 
the top of the pos- 
terior fossa, thus 
Fig. 56. 
A vertical, transverse section of the Cranium, a The 
skull, b The dura mater, c The arachnoid mem- 
brane. F The falx cerebri. 
Part II.—What is included in this system? Section I,—82. What are 
the three membranes which inclose the brain ? Describe the dura mater. De- 
scribe the three partitions of the brain produced by the dura mater. THE BRAIN. 
75 
separating the cerebrum from the cerebellum. Another 
partition, which is called the falx cerebri (1, Fig. 57), 
arises from the eth- 
moid bone, follows 
along the sagittal 
suture, and becom- 
ing wider as it 
extends backward, 
terminates at the 
tentorium. Anoth- 
er much smaller 
fold of the dura 
mater, called the 
falx cerebelli, ex- 
tends from the ten- 
torium to the mag- 
num foramen. 
Fig. 57. 
1 The falx cerebri. 2, 2 Two large veins by which the 
blood is returned from the head. 3 The forehead. 
83. The arachnoid membrane is an exceedingly thin 
film, and is attached to the interior surface of the dura 
mater. It secretes a fluid in small quantity, but sufficient 
to keep the surface moist, and diminish the friction occa- 
sioned by the slight motion of the brain within the cra- 
nium,38 
84. The pia mater isia thin but firm membrane not 
attached to the arachnoid or the dura mater. It lies next 
to the brain, dipping into its substance at the fissures, and 
forming the only proper envelope of the brain. 
28 There is a constant secretion of this fluid and as constant an absorp- 
tion of it. This membrane, in certain conditions of the system, and par- 
ticularly in childhood, is apt to take on inflammation, when the secretion 
becomes too abundant, and results in dropsy of the head (hydrocephalus). 
83. Describe the araehnoifl membrane. What ie its office ? 
84. Describe the pin mater. * 76 
THE BRAIN. 
85. The brain occupies nearly the whole cavity of the 
cranium. It is,divided into right and left hemispheres, 
the falx cerebri lying between them. The base of the 
brain is divided on each side into three lobes, correspond- 
ing with the three depressions in the base of the cranium. 
That portion which lies in the posterior fossa and under 
the tentorium, is the cerebellum ; the remaining, and by 
far the largest portion, is the cerebrum. 
II. General Structure of the Brain. 
86. The medulla oblongata (Fig. 58), though not a 
Fig. 58. 
Fig. 59. 
part of the brain but 
of the spinal cord, of 
which it is simply a 
prolongation above the 
magnum foramen, is 
situated within the cra- 
nium. It continues of 
nearly the same size as 
the spinal cord for 
about an inch, and then 
becomes enlarged into 
a bulb (a) called the 
pons varolii. 
1,1 The integuments of the head turned down. 
2, 2 The edge of the remaining part of the 
cranium, the upper part having been re- 
moved. 3 The dura mater. 4 The convo- 
lutions and aufractuosities of the brain. 
85. Where is ihe brain situated ? State the divisions of the brain. 
86. What besides the brain does the cranium contain} Describe it. THE BRAIN. 
77 
87. The external surface of the cerebrum presents nu- 
merous irregular elevations, called convolutions (4, Fig. 59), 
which are separated by depressions (anfractuosities). These 
depressions are better 
seen in the horizon- 
tal section, Fig. 60, 
and are produced by 
folds of the pia mater 
dipping down for 
half an inch or rather 
more into the sub- 
stance of the brain. 
88. The two hem- 
ispheres of the cere- 
brum are connected 
a white fibrous 
substance, the cor- 
pus callosum (e, 
Fig. 65), situated be- 
low the falx cerebri. 
Its fibres run trans- 
versely, as seen at 
ded, Fig. 61. Be- 
tween the corpus 
callosum and the base of the brain are five cavities called 
ventricles, the larger two of which are seen at 5, 5, Fig. 60. 
Fig. 60. 
A horizontal section of the Cranium and Cerebrum. 
1,1 The cranium. 2, 2 The dura mater. 3, 3 The 
cellular substance of the cerebrum. 4, 4 The tu- 
bular substance. 5, 5 The lateral ventricles of 
the brain. 
89. The brain is composed of cellular and tubular 
substances. The first is a gray, ash-colored, pulpy mass, 
the other is dense, white, and fibrous. In the cerebrum 
87. Describe the external surface of the brain. 
88. How are the hemispheres of the brain connected? Describe the corpus 
collosum and the ventricles. 
89. Of what is the brain composed? Describe these two substances. How 
are they situated in the cerebrum ? In the medulla oblongata ? In the cerebel- 
lum ? 78 
THE BRAIN. 
the cellular or gray substance is exterior (3, 3, Fig. 60), 
lying immediately under the pia mater, and following it 
wherever depressions of that membrane occur. The tubu- 
lar or white substance (4, 4) constitutes the central por- 
Fig. 61. 
Fig. 62. 
A cross section of the 
spinal cord. The dark 
portions represent 
' the cineritions por- 
tion. The cineritious 
portion is found in 
the central part of the 
medulla oblongata 
also. 
tion of the cere- 
brum. In the 
medulla oblonga- 
ta the gray por- 
tion is • central, 
and the white ex- 
terior (Fig. 62). 
In the cerebellum 
the two sub- 
stances are ar- 
ranged in con- 
centric ’ layers, 
giving, when a 
vertical section is made, the branching appearance (seen 
above, b c in Fig. 65) called the arbor vitce. 
A horizontal section of the Brain at a higher level than 
the preceding section, a b c The white substance. 
f The gray portion, d e d The corpus callosum. 
III. Functions of the Brain. 
90. The brain is a pulpy mass, distinguishable into parts 
90. What reason have we for supposing that the brain is a highly organized 
substance ? Can we, from a study of its organization, determine its functions f 
In what way are we to determine its functions ? What are they 7 THE BRAIN. 
79 
by differences in color and structure ; but it has not, like 
the skeleton, the muscles, or the eye, such a relation of 
parts that we can see their adaptation to the offices which 
they perform. The care, however, witli which the brain is 
protected, the amount of blood with which it is supplied, 
and the connection existing between the health or disease 
of the brain and the proper or disordered action of other 
parts of the system, lead us to believe that it has a highly 
complex and perfect organization. But the most accurate 
examination of its intimate structure has thrown no light 
upon the mode of its operations. We cannot, therefore, as 
we can in most other parts of the system, study its organ- 
ization, and from this infer its functions. These we are 
left to determine simply from the phenomena which it 
exhibits.29 These phenomena justify us in regarding it as 
a repository of power and as the organ of the mind. 
91. The brain does not, so far as we know, originate any 
of the forces of the system, such as those upon which 
29 This we ought to expect from the peculiarity of its functions. Con- 
sidering it as the organ of the mind, what possible adaptation can we 
conceive 1 It is conceivable that beings, in other respects like us, should 
have been created without hands (or any other important organs would 
serve for illustration), and they would be able to form Some idea of the 
kind of organization which would be necessary to fit us for prehension, 
just as we can study out the best construction of a loom, or a steam-engine. 
But a statement of the question as to the organization adapted to the 
operations of the mind, makes the thing at once ludicrous. What organ- 
ization, for instance, would he a suitable one to enable the mind to have 
the feeling of pain, or the perception of form or color. 
The relations of mind do matter—the way by which they affect each 
other—are so completely beyond the comprehension of man, with his pres- 
ent capacities, that it is only surprising that the idea should ever have been 
entertained of discovering in the organization of the brain any adaptation 
to its functions. 
91. Is the brain the source of power ? What agency has it in reference to the 
forces of the system 80 
digestion, the circulation, and other phenomena of life 
depend. But, however these involuntary forces are origin- 
ated, it is a repository of them; it appropriates and con- 
trols them. Hence when the brain is diseased, these phe- 
nomena of life are more or less disturbed. The brain does 
not, however, exert this control by means of the mind. 
These actions are removed from the control of the mind, 
and such removal is essential to life; for the mind requires 
rest and sleep, and all the operations which depend upon 
it must, during this suspension of mental activity, be sus- 
pended. 
THE BRAIN. 
92. But the most important function of the brain con- 
sists in its being an organ of the mind.30 This, in fact, 
embraces three functions, for the mind may be acted upon 
by external objects, it may act upon them, or it may be 
active with its own ideas, without reference to its relation 
to external objects. That is, the brain is the organ of the 
mind in sensation, in volition, and in reasoning. 
93. The brain is the organ of the mind in sensation. 
The mind is acted upon by external matter through the 
agency of the senses. We can trace the operation of physi- 
cal agents, such as light, odors, etc., till they have reached, 
30 The preponderance of facts compels ns to come to this conclusion, 
though there are remarkable cases of injury to the brain without perma- 
nent, and often without temporary, derangement of the mental operations. 
Thus, the skull may be broken, or parts of it shot away, and a large 
amount of brain removed without producing idiotcy or insanity. In Ver- 
mont, a few years since, a rod of iron of an inch in diameter, and two 
feet long, was driven, by the unexpected discharge of gunpowder, through 
a man’s head, entering the face and coming out near the top of the head 
on the opposite side, and yet the man recovered both his health and his 
reason. 
92. What is the most important function of the brain ? W7hat three objects 
does it accomplish as such ? 
93. How far can we trace the operation of physical causes in producing sensa- 
tions ? Can we see in what way tne brain operates in producing sensations ? THE BKAIif. 
81 
through the appropriate organs, the nerves of sensation, 
when the mind comes at once to the sensation and per- 
ception of the external object. If the nerves which con- 
nect these organs of sense with the brain be impaired, 
this state ot mind does not follow. We may, therefore, 
regard the brain as the organ of the mind in becoming 
aware o 1 the existence and acquainted with the properties 
of external objects.31 
94. The mind cannot affect external matter directly. 
Whatever effects it produces are the result of contraction 
and relaxation of the muscles. The power is not, how- 
ever, in the muscles themselves; for if the nerves which 
connect them with the brain be severed, the muscles are 
no longer capable of contraction and relaxation. It is 
equally true that the power does not consist in the mind, 
the will; for after we have put forth power for a limited 
time we become exhausted, and when this exertion has 
been continued long enough, the most vigorous efforts of 
the will fail to cause contraction and relaxation of the 
muscles; the power which the mind had before controlled 
31 This inference rests upon the fact that whenever we can trace these 
physical causes up to the brain, this also being in a healthy state, the next 
thing of which we are aware is a certain state of mind. The brain lies be- 
tween the organ of sense (as the eye, for example) and the mind. Hence 
we must regard the brain as essential to the result—as having something 
to do—as part of the machinery. In what way it is essential is a matter 
in which we are, and must remain, profoundly ignorant. 
It is proper here to remark that this is not a case standing by itself in 
any important respect. We know as little why fuel will burn, or any other 
phenomena take place. We can establish the conditions of combustion 
and see the event follow. Why such event follows such conditions we 
know not; and we are compelled to regard the result as always the direct 
work of uncreated power. 
94. How does the mind affect external objects ? Is the power in the mus- 
cles ? Is it in the mind ? How is this proved ? What agency has the brain in 
reference to this power ? 82 
THE BRAIX. 
is spent. When sufficient time and' other means have been 
furnished for replenishing the available vital force, the 
mind again possesses power over the muscles. The brain 
is then the means by which the mind manifests its volitions 
in producing muscular motion. 
95. By means of the senses we obtain the ideas of color, 
form, weight, taste, sound, etc. These original ideas sug- 
gest necessarily others, such as that of our own existence, 
of a material world, of a First Cause, etc. All these ideas 
are variously connected with emotions, such as pain, de- 
light, gratitude, aversion, etc. These ideas are the furni- 
ture which the mind receives directly and indirectly from 
the external world. All these ideas we can recall, com- 
pare, and reason upon. These operations of reasoning pro- 
ceed, to a certain extent, in a uniform manner. There is 
a great diversity, but still there is what we call a rational 
state of mind, in opposition to one which we should call 
insanity. The mind reasons in a uniform manner, obeys 
certain laws in its mental processes, unless the brain has 
suffered injury. In a diseased or mutilated condition these 
operations become irregular, and the person is insane. In- 
sanity is a diseased condition of the brain. In the rea- 
soning processes of the mind we may, therefore, consider 
the brain as the physical agent. 
96. Such are the general functions of the brain, or per- 
haps we should say, the brain and spinal cord. It is not 
necessary in this place to inquire as to the special func- 
tions of particular parts of the cerebral system, since we 
may, without such inquiry, learn its general functions, and 
the practical rules to be observed in reference to it. 
97. The first principle of practical importance is that 
95. How do we obtain the ideas of color, form, etc, ? What other ideas do 
these suggest ? What us6 do we make of these ideas ? In these reasoning pro- 
cesses, how is it shown that the brain is the physical agent ? 
97. What is the first condition in order that the brain properly perform its THE BEAIN. 
83 
the brain, in order to perform its functions properly, 
must be exercised. The same principle which governs 
the other parts of the physical system should govern the 
brain. It is as natural for the child 'to think as it is for 
him to play, and the fact that both promote his happiness 
is proof that both are proper and necessary for him. Indo- 
lence of the brain, like indolence of the muscular system, 
may, however, from circumstances, become a habit. It is 
the restlessness, the absence of enjoyment thus relinquished 
which, in a large proportion of cases, drives the individual 
to seek the stimulus of intoxicating drinks. But the 
teaching of nature is to employ the brain in thought, and 
thus escape the necessity of such stimulants. 
98. This natural tendency to think will, when properly 
guided, as certainly develop the mental faculties as proper 
use of the limbs will develop bodily strength. To do this 
is the main object of general education. In order to guide 
this tendency aright, it should in the first place be allowed 
scope; it should not be repressed. And hence the inquisi- 
tiveness of children, even if it be sometimes troublesome, 
should be allowed a wide range, and should often be stimu- 
lated. The gratification of this curiosity and inquisitive- 
ness is the reward of effort by which oiir Creator would 
stimulate us to new effort.33 In the second place, the 
3:1 This reward always follows effort. The complaint often made by 
scholars that their studies are uninteresting, generally rests upon the fact 
that the studies have not been attended to with sufficient care. The 
truths have not been comprehended. Everything of the nature of mental 
acquisition must, from our constitution, give us pleasure. Not that it will 
give every person the same degree of pleasure, for there are obviously differ- 
ent susceptibilities to pleasure—and there are -diversities of taste, so that 
equally susceptible persons will enjoy different kinds of mental occupation 
functions ? What is the natural inducement to exercise the brain (that is, to 
think) ? To what physical evils does neglect of it lead ? 
98. For what was this tendency to exercise the brain given ns? What arc 
the three rules by which it should be guided ? 84 
THE BRAIN. 
brain should be allowed the necessary relaxation, so as not 
to become exhausted, and thus awaken a dislike for re- 
newed effort. In the third place, its exercise should be 
varied within certain limits, so as to give diversity of occu- 
pation, and yet not so much or so frequently as to dis- 
courage continuous and earnest application. 
99. But besides a general activity of the brain, it is pos- 
sible to give it special skill. It is like the enlargement of 
the muscles to fit a man for any particular employment. 
Perhaps the exercise of the brain will not increase its size, 
but it is certain that it will increase its power in any given 
pursuit. We see this increase of power in the salesman, 
the accountant, the politician, the enthusiast in any em- 
ployment. This is a prominent object of professional 
education.33 The brain is as subject as any other physical 
organ to that wonderful law of habit; it acquires skill, 
power, and ready obedience to the will by effort continually 
repeated.34 
very differently. The general principle, however, is still sustained, that 
knowledge always pleases, and it is the observation of all teachers, that 
those who apply their minds with the most assiduity, are the ones who 
most enjoy their studies. 
33 In many respects a general and professional education are the same 
thing. It is not possible to train and discipline the mental powers gener- 
ally, without doing something toward preparing the individual for pro- 
fessional success. Nor is it possible to confine the attention to strictly 
professional study without increasing generally the mental powers. It is 
true also that facts must be learned in both general and professional study. 
Still, there is the broad and important distinction between general and 
professional education that the one proposes the general discipline of man 
as a thinking being, and the other proposes a special discipline, as a pre- 
paration of him for a limited and prescribed course of life. To confine 
education to the first, would be like securing a large muscular develop- 
ment, while the individual is ignorant of any of the processes of useful 
99. What advantage does the brain receive from special training? Will it 
increase the volume of the brain ? Give instances in which special power is 
acquired. In what does this special training consist ? THE BEAIH. 
85 
100. The brain may also be overworked. It is probable 
that by the action of the brain there is a disorganization, 
to some extent, of its substance, as there is in the muscles 
by their action. There is evidently some physical state of 
the brain, induced by too prolonged activity, wnich unfits 
it for longer continued effort until time has been given for 
reparation. This state is indicated by a disposition to knit 
the brows, more or less of pain in the head, and sense of 
fatigue. These are intimations from our constitution that 
rest is necessary and ought not to be disregarded. The 
too ambitious student, or the too eager business man who 
disregards these indications, will inevitably suffer the pen- 
alty in later years. " 
To defer this period of weariness, resort is not unfre- 
qnently had to artificial stimulants; and they may have 
this effect, but it is an obvious disregard of a natural 
warning of the exhausted condition of the system; to 
silence the warning of danger while the danger is not only 
present out increasing, must be both unwise and unsafe. 
101. The exercise of the brain depends not merely upon 
the will. There must be general physical health and the 
physical employment. To limit education to the last would be analogous 
to training an individual to the intricate processes of a difficult trade, when 
he has not general muscular power enough to make his skill of any avail. 
The danger is very great, to young men in this country, of hastening too 
rapidly from general study to professional study. They always regret, in 
later life, that the foundations of their education were so slender, but the 
regrets often come when it is too late to apply a remedy. 
34 Certain teachers who have been remarkably successful, have owed 
their success to the tenacity with which they insisted upon frequent repe- 
tition of lessons, review upon review, till the leading principles of a branch 
of study are ground into the mind, so that they can never be forgotten. 
100. To what danger is the brain liable ? What effect does activity of the brain 
produce in the brain? How is this state indicated? How may this period of 
weariness be deferred ? Why should it not be ? 
101. What besides the will dees the exercise of the brain depend upon ? Why 86 
THE BRAIN". 
observance of those conditions'by which general health is 
preserved. Special importance is, however, to be attached 
to the preparation of the blood, of which a much larger 
amount is sent to the brain, in proportion to its size, than 
to any other organ. For if the blood is impure it operates 
directly in proportion to the extent of the impurity, to 
bring on inactivity of the brain, and finally utter prostra- 
tion and stupor. The preparation of the blood depends 
upon its being properly subjected to the action of oxygen 
in the lungs, that is, it depends upon the quantity and 
purity of the air we breathe. Hence, sleeping-rooms, 
school-houses, and workshops should, wherever it is possi- 
ble, be large, and, in all cases, well ventilated. The sub- 
ject of proper ventilation should be specially attended to 
in churches and other rooms intended for the accommo- 
dation of large audiences. 
102. Cases occur in which the brain has a naturally 
excessive activity. If this is not of itself disease, it is 
always liable to terminate in disease. Children of more 
than ordinary capacity, especially if there is an obvious 
precocity of intellect, should not be stimulated to exertion, 
but should be held to some extent in check, and their 
attention should be turned, not, however, in such a way 
as to attract the notice of the child and make him aware 
of the purpose, to a large amount of physical effort, and 
in the open air. This is more important, because this pre- 
dominating development and activity of the brain is most 
frequently found in children of a generally weak physical 
organization and of scrofulous tendencies. 
103. The successful intellectual activity of the brain 
is pure blood necessary ? What does the proper preparation of the blood depend 
upon ? What practical rules does this suggest ? 
103- What is the last condition of the proper exercise of the brain ? 
102. Can the brain have an activity too great tc co sist with health ? What 
caution does this suggest ? THE SPINAL CORD. 
87 
depends in a great measure on the predominant emotions. 
No person can think vigorously and reliably with a habit- 
ually desponding and melancholy temperament. Such a 
state, if prolonged, is a diseased one, and is to be treated as 
such. Our Creator has established a generally hopeful 
tendency in the healthy mind. It is only when buoyant 
emotions are prevalent that the brain can be active, with- 
out leading to morbid, unsocial, morose, and perhaps in- 
sane condition of the mind. 
Section II.—The Spinal Cord. 
101. The spinal cord is the continuation of the medulla 
oblongata from the magnum foramen to the sacrum. It is 
divided by deep fissures in front and behind (3, 2 Fig. 63), 
>Fig. 63. 
Fig. 64. 
1 The spinal cord. 2,2 The 
depressions on the front 
and back sides. 3, 3 The 
spinal canal. 4. 4 The 
membranes extending 
to the sides of the canal 
by which the cord is 
supported. 
1 The spinal cord. 2. 2 The pia mater. 3, 3 The 
ligaments by which the spinal cord is retained in 
its place. 4. 4 Points by which the ligaments are 
attached to the walls of the spinal canal. 
into right and left halves, and by slight depressions on the 
sides, into anterior and posterior portions. The central 
Section ITn—104. Descr!be the position of the spinal cord. Its divisions. 
Its composition. Its membranes. The means by which it is retained in its 
place. 88 
THE SPINAL CORD. 
portion is composed of gray substance (see Fig. 62), as in 
the medulla oblongata, and the exterior of white sub- 
stance. The dura mater and arachnoid membrane form a 
lining to the spinal canal. The pia mater forms a sheath 
which incloses the spinal cord. This cord is smaller than 
the canal in which it is inclosed. The space between the 
cord and the sides of the canal is filled with a fluid secre- 
tion from the arachnoid membrane, and the cord is re- 
tained in its position by folds of the pia mater (3, 3 Fig. 
64), which are prolonged at points (4, 4), so as to be at- 
tached to the sides of tlie spinal canal. 
105. We may now inquire more fully into the functions 
of the white and gray parts of the nervous system. 1st, 
the white substance It is fibrous in appearance, and 
the fibres are found to be minute tubes, which are regarded 
as channels of communication from the points where they 
originate to the points where they terminate. One class 
of these tubes is so constituted as to be acted upon only at 
the extremity most remote from the brain. They receive 
impressions from light, heat, vibrations, etc., and carry 
these impressions to the brain. They are called afferent 
nerves. Another class of nerves is acted upon only at 
the extremity which is in the brain or some other nervous 
centre. They carry outward to the muscles the impres- 
sions of volition, and thus produce the several motions of 
the body. They are called efferent nerves. But in 
both cases they are mere carriers. 
106. These tubes of white substance escaping from a 
nervous centre are continuous in the nerves throughout 
105. What is the structure of the white substance ? What is its function ? 
What is the peculiarity of the afferent nerves ? What of the efferent nerves ? 
106. Does a single nerve ever, by its branches, communicate with two or 
more nervous centres ? How are the nervous centres connected f Give 
instances. THE SPINAL CORD. 
89 
their whole extent; that is, they do not receive or give 
off branches. A tube traced backward from a given point 
of the finger is a single tube till it reaches its nervous 
centre. But the several parts of these nervous centres are 
united by a very abundant amount of these fibres of com- 
munication. Thus the white substance of the two hemi- 
spheres is united by the corpus collosum. The white sub- 
stance in the halves of the cerebellum is united by the 
cross fibres of the pons varolii (Fig. 58, a). A part of the 
fibres of the spinal cord cross at the magnum foramen, so 
that both hemispheres and both parts of the cerebellum 
are connected with both halves of the spinal cord. The 
great sympathetic we shall find connected, in like manner, 
with all of the other parts of the nervous system. 
107. Secondly, the gray substance. It consists 
mostly of cells, which seem to be undergoing constant 
change. It is the source or the repository of all the power 
of the system. 
In the hemispheres it is the organ of all thought, whether 
manifested in memory, reasoning, intuition, volition, or 
motion—the white fibres receiving from it impressions 
which they distribute as may be required. 
It is also the recipient of all impressions which the af- 
ferent nerves convey. In this substance, therefore, all sen- 
sation takes place, all knowledge of the external world is 
produced. 
108. Experiments seem to indicate that the function of 
the gray substance of the cerebellum is in regulating vol- 
untary motions. It does not produce motion, but it ad- 
justs it, as in the complicated acts of balancing the body 
in walking, the movements of skill in penmanship and 
107. What is the function of the gray substance ? What is its function in the 
hemispheres of the cerebrum ? 
108. What is its function in the cerebellum ? 90 
THE SPINAL CORD 
other arts, and the control of the muscular movements 
upon which the modifications of voice depend. 
109. The gray substance of the medulla oblongata fur- 
nishes the involuntary force upon which the movements of 
respiration and circulation depend The gray substance 
of the spinal cord determines the involuntary motions of 
the body generally. Thus the medulla and spinal cord 
are independent nervous centres, and the white substance 
transmits tlie power thus furnished. But it is only a por- 
tion of the white fibres that are thus used Others go to 
the brain, and thus establish relations between the centre 
of intellect and other parts of the body.55 
36 If the hand or foot be irritated, an impression is conveyed by the sen- 
sory nerve to the spinal cord, and immediately the corresponding motor 
nerve communicates a convulsive movement to the corresponding muscles. 
Hence the motion is called reflex motion. It depends on the spinal cord 
alone, for if this cord be divided both above and below the origin of these 
nerves, the reflex motions are still produced. The movements of respira- 
tion, the action of the heart, and the involuntary motions generally, are 
of this reflex kind. 
The discovery of this independent function of eacn portion of the spinal 
cord establishes a close resemblance between it and the ganglionic sys- 
tem of the lower orders of the animal kingdom. If the anterior and pos- 
terior parts of a centipede be cut off, it will still continue to crawl, the 
ganglion corresponding with each pair of legs acting as an independent 
nervous centre to give them motion. But the motion in this case will be 
invariably in a straight line, regardless of obstacles. The same insect 
has in the head a ganglion larger than the rest, called the cephalic gan- 
glion, with which every pair of legs also communicates ; and when this 
communication exists, the animal will move by the reflex action of the 
other ganglia, and yet it will avoid obstacles. Hence we must regard this 
cephalic ganglia as the scat of intelligence, though it may be of a very low 
order. 
We should then conclude that the functions of mere animal life reside 
in the spinal cord, and that all mental functions belong to the cephalic 
ganglion. This is true in all the grades of animal life. Such is the 
109. What is its function in the medulla ? What in the spinal cord ? 91 
THE HERYES. 
Section III.—The Nerves. 
110. The nerves are small white cords which pass out in 
pairs from the brain and spinal cord, and spread themselves 
through every part of the body. Like the spinal cord, 
Fig. 65. 
A longitudinal and vertical section of ttie Brain, and a side view of the Medulla 
Oblongata, a a a The cerebrum, b The cerebellum, c d The spinal cord. The 
medulla oblongata is its extension upward, e The corpus callosum. 1 The 
olfactory nerve. 2 The optic nerve. 3 The motor oculi. 4 The trochlearls. 
5, 5', 5" The trigemini. 6 The abductor oculi. 7' The auditory nerve. 7 The 
facial nerve. 8 The glosso pharyngial nerve. 8' The par vagnm. 8" The 
spinal accessory nerve. 8 The hypo-glossal nerve. 10,■ 11, 12 Spinal nerves. 
structure in the worm, the butterfly, the honey-bee, and the spider. Such 
is also the structure in the vertebrate animal. Even in this class, in its 
least development, there is no brain, scarcely even a cephalic ganglion. 
But as the animal rises higher in the scale of intelligence, the cephalic 
ganglion becomes larger, separate parts become distinguishable as the 
animal comes to possess a separate and peculiar character, and finally we 
have in man the largest brain and the fullest mental powers. 
Section III,*-110. Describe the nerves. What is the first class of nerve* 2 92 
they are composed of gray and white matter, and are in- 
closed in sheaths, which are formed by extension of the 
three membranes which inclose the brain. 
THE HERVES. 
I. The Cranial Nerves. 
111. There are nine pairs of nerves which pass out 
through the cranium: ✓ 
(a) The olfactory (1, Fig. 65), arises from the fissure 
between the anterior and middle lobes of the brain. It 
passes out, by several fasciculi, through the perforations in 
the ethmoid bone, and is distributed to the different parts 
of the nose. 
(h) The optic nerve (2), arises from the middle lobe, 
and enters the orbit of the eye through the optic foramen. 
(c) The motor oculi (3), arises just in front of the 
pons varolii, enters the orbit, and is distributed to most of 
the muscles of the eye-ball. 
(d) The trochlearis (4), arises from the side of the 
pons varolii, enters the orbit,, and is spent upon the supe- 
rior oblique muscle of the eye. 
(e) The trigemini (5, 5', 5”), arises from the pons 
varolii, a little below the origin of the trochlearis, by three 
roots, and passes out of the cranium by three branches, and 
is distributed to the ball of the eye, to the eyelids, to the 
interior of the nose, to the gums and teeth of the upper 
and lower jaws, to the tongue, and to the ear. 
(/) The abductor oculi (6), arises from the anterior 
portion of the medulla oblongata, below the pons varolii, 
passes to the orbit, and is spent on the external straight 
muscle. 
(g) This pair consists of two nerves,36 the auditory 
36 There is no reason why this pair should not be regarded as two 
pairs, except the fact that they escape from the cranium together. The 
111. Describe the origin and distribution of the olfactory nerve. The optic 
nerve, etc. What is the second class of nerves ? THE HERVES. 
93 
and facial (7, 7'), which arise 
from the medulla below the 
pons varolii. The auditory 
portion passes through the tem- 
poral bone to the interior of the 
ear, where it terminates. The 
facial portion winds through 
the cavities of the temporal 
bones till it escapes in front of 
the mastoid process. It is dis- 
tributed to the face. 
Fig. 66. 
'{h) The eighth pair is com- 
posed of three nerves (8, 8', 8"), 
the glosso - pharyngeal, 
which arises from the middle 
of the posterior part of the me- 
dulla oblongata; the par va- 
gum, which arises a little below 
the preceding; and the spinal 
accessory, which arises from 
the posterior part of the spinal 
cord for two or three inches 
below the magnum foramen, 
and passes up into the cranium. 
These three nerves pass out .of 
the cranium together. The 
first branch is distributed to 
1,1 The cerebrum. 2. 2 The cere- 
bellum. 3 The medulla oblongata. 
3, 4 The spinal cord. 5 The dor- 
sal nerves. 6 The sacral nerves. 
7 The axillary plexus. 8 The 
lumbar plexus. 
auditory and facial portions are distinct in their origin, as will be seen 
from the figure. They are different in structure, one being a dense, firm 
nerve, and the other very soft. They are entirely different in their distri- 
bution and functions. One goes to the face, and the other to the ear. 
One is a nerve of sensation, and the other of motion. The same might 
he said generally of the three portions of the eighth pair. Accordingly, 
many anatomists represent the cranial nerves as consisting of twelve, in- 
stead of nine pairs. THE DEBYES. 
the tongue and pharynx, the second to the lungs and 
stomach, and the third to the muscles of the neck. 
(i) The hypo-glossus (9) arises from the lower ante- 
rior portion of the medulla oblongata, and is spent upon 
the tongue. 
II. The Spinal Nerves. 
112. There are thirty pairs of nerves which arise from 
the spinal cord (Fig. 66). 
(a) The sub-occipital nerve escapes from the spinal 
cord between the occipital bone and the atlas. 
(b) The cervical nerves, of which there are seven 
pairs, escape through the intervertebral foramina, below 
each cervical vertebra. 
(c) The dorsal nerves, of which there are twelve 
pairs, come out from the spinal cord below each dorsal 
vertebra. 
Fig. 67. 
(d) The lumbar 
nerves, five pairs, es- 
cape below each lumbar 
vertebra. 
(e) The sacral 
nerves, of which there 
are five and often six 
pairs, escape through the 
foramina of the sacrum. 
113. Each of the spinal 
nerves arises from the 
spinal cord by two roots 
{b, c, Fig. 67,) one of 
which comes from the 
a The spinal cord, b c The two roots of which 
each spinal nerve is formed, d The ganglion 
formed on each posterior root, e The nerve 
after the junction of the two roots. 
112. How many pairs of spinal nerves are there ? Give the origin and each 
division of these nerves. 
113. How do these nerves arise from the spinal cord ? What Is the peculiarity 
of each posterior root ? How is the whole nerve finally formed ? THE HERYES. 
95 
Fig. 68. 
General distribution of the nerves of the system. 96 
THE NERVES. 
anterior and the other from the posterior portion. The 
posterior root, b, forms a ganglion; that is, an enlargement 
of the nerve into an oval form, d, just after the nerve es- 
capes from the intervertebral foramen. At a little distance 
from the ganglion the two roots unite to form one nerve, 
e, and every branch of the nerve in its distribution through 
the body contains fibres of each root. 
114. The sub-occipital nerve and the first three cervical 
are distributed to the muscles of the neck and the integu- 
ments of the head. 
The four inferior cervical and the first dorsal nerves 
unite to form the axillary plexus (7, Fig. 66), (a network of 
veins, Fig. 69, produced by 
division of nerves into several 
branches, and their crossing, 
recrossing, and interlace- 
ment), from which the nerves 
of the upper extremities pro- 
ceed. 
Fig. 69 
All the dorsal nerves (5), 
except the first, are distrib- 
uted to the muscles and in- 
teguments of the back, tho- 
rax, and abdomen. 
The lumbar nerves (8) 
form the lumbar plexus which rests on the spine in the 
lower part of the abdomen. This plexus furnishes the 
nerves to the muscles and other parts contained within 
the pelvis. 
A plexus or network of nerves. 
The sacral nerves form the sciatic plexus, which is situ- 
114. What are the nerves which supply the neck and head ? How are the 
upper extremities supplied ? What is a plexus ? What is the distribution of 
the dorsal nerves ? What of the lumbar nerves ? How are the lower extremities 
supplied ? THE NEEVES. 
97 
ated below the lumbar plexus and within the pelvis. It 
furnishes the nerves to the lower extremities. 
115. Such is the general distribution of the nerves of 
the head and spine; but throughout the system they in- 
terchange filaments so frequently, that a common sympa- 
thy is established between all parts of the body. 
III. The Great Sympathetic Nerve. 
116. This nerve (Fig. 70) consists principally of a chaii 
of ganglions, situated on each side of the spinal column 
in the neck, thorax, abdomen, and pelvis. Three of these 
ganglions are placed on the cervical vertebrae, twelve on 
the dorsal, five on the lumbar, and generally three or four 
on the sacrum. The ganglions are connected together by 
short nerves. Each spinal and several cranial nerves send 
filaments to the ganglions. It is then a system of gang- 
lions connected together and to the general nervous centre 
of the body, at a large number of points, by nerves; and 
from it arise, at different points, other nerves having pecu- 
liar functions, and distributed to the lungs, the heart, the 
arteries, and to the viscera of the abdomen. 
IV. Functions of the Nerves. 
We have before spoken of the afferent nerves, which are 
nerves of sensibility, and of the efferent nerves, or nerves 
of motion. But for our present purpose they may be di- 
vided, according to their functions, into four classes. 
117. (1.) The nerves of special sensibility. These 
are the olfactory nerve, which conveys only the impression 
of odors; the optic, which conveys only impressions of 
115. What is the effect of the interchange of filaments between the nerves't 
116. Describe the great sympathetic nerve. What is the distribution of the 
nerves coming from the great sympathetic ? Into how many classes are the 
nerves divided ? 
117. What are the nerves of special sensibility 1 How are those sensations 
accounted for, when there is no external object corresponding with the sensa- 
tion ? 98 
THE NERVES. 
The system of the Great Sympathetic Nerve. A a The ganglion and solar plexus, situated behind the stomach, 
n n Thoracic ganglia, p c e External and internal nervous filaments. G h The coronary plexuses, situated on the 
heart, i The lower cervical ganglion, n The middle cervical ganglion, q The upper cervical ganglion. 1 The renal 
plexus, situated on the kidneys. 2, 3 Lumbar ganglia. 3, 4 Nervous filament from them. 5, 5 The aortic plexus. 
Fig. 70. THE NERVES. 
99 
light; the lingual branch of the fifth pair, which conveys 
only impressions of taste; and the auditory, which con- 
veys no other impressions than those of sound. 
Under peculiar circumstances these nerves may be af- 
fected by other means than those which ordinarily excite 
them. Thus, there may be a sensation of light occasioned 
by a galvanic shock.37 There may be a sensation of distant 
thunder, or of ringing of bells, or music, occasioned by a 
diseased state of the head. It is to be supposed in such 
cases that the nerve, by unusual means, is brought into 
the same state into which it would be brought by the pres- 
ence of its ordinary stimulus. The inference then is, not 
that the nerve is insensible to the influence of other physi- 
cal agents, but that by whatever agent it may be acted 
upon, it can convey to the brain only particular impressions, 
those for which it is specially fitted. 
118. (3.) The nerves of general sensibility. The 
fifth pair, or trigemini, with the exception of the lingual 
branch, is the nerve of general sensibility to the organs 
of the senses. It cannot convey the impression of odors, 
light, taste, or sound. Its action is, however, necessary in 
producing these impressions; for when it is severed or 
injured, the nerves of special sensibility lose the power of 
conveying their appropriate impressions. 
119. The posterior roots of the spinal nerves are the 
nerves of general sensibility of the body. These nerves 
convey the general sensations of pressure, temperature, 
form, weight, etc.38 
37 For a similar reason, a person who has fallen upon his head will de- 
scribe the sensation by saying that he “saw stars.” 
118. What is the second class of nerves ? Describe the functions of the fifth 
pair. 
38 The mind always refers the sensations produced by these nerves to 
119. What are the spinal nerves of general sensibility? What are the func- 100 
THE NERVES. 
There is another class of sensations referable probably 
to these nerves, and yet not with certainty. They imply 
particular conditions of the body, and are in many cases 
of the nature of overseers to notify us of our wants. Among 
these sensations are those of hunger, thirst, nausea, fatigue, 
and several others. 
Besides these definite sensations, there is an indistinct 
and diffused sensibility depending upon the nerves. They 
may be so active as to produce extreme excitability, or they 
may be so inactive as scarcely to convey to the mind the 
impression of the continuance of life, an absence of sensi- 
tive enjoyment. The state intermediate between these 
two is the only one consistent with health and efficiency; 
one in which there is a feebly observed but constant com- 
munication between the surface of the body and the mind 
—such an amount of sensation as to result in the general 
feeling of satisfaction and contentment. 
120. These nerves also act the part of sentinels. We 
have seen that they are most abundantly supplied at the 
surface of the body, and it is from without that danger is 
mostly to come. The pain which they cause when the 
surface is injured is both the warning of our danger and 
the motive to attend to it. These sentinels are in every 
part of the surface of the body, so that the point of a 
needle cannot be put down where they will not be found, 
the extremity of the nerves. Thus, a person whose limb has been ampu- 
tated will, when the remaining part of the nerve is affected, refer the sen- 
sation of pleasure or pain to the part in which those nerves terminated 
while the limb existed. 
tions of these nerves ? What sensations are referred provisionally to them ? 
Describe the diffused sensibility referable to them. 
120. How do these nerves act as sentinels ? Why are they most abundant at 
the surface ? In what respects are they an evil ? How is this evil overbalanced 
by advantage ? Is the evil as great as is generally supposed ? How may it be 
overcome ? THE NERYE3. 
101 
and their warning is instantaneous, authoritative, and gen- 
erally proportioned to the danger. To realize their impor- 
tance, we have only to reflect how constantly and seriously 
we should be exposed to injury from burns, wounds, 
bruises, etc., if we were deprived of this kind of warning. 
It is true that these nerves may also sometimes be very 
much in our way. Thus, in case of amputation or other 
surgical operation, much suffering necessarily results from 
the sensitiveness of these nerves, without, so far as we can 
see, any direct advantage. But, in the first place, the sen- 
sitiveness from which we suffer under such circumstances 
has been the means of preventing the necessity of such 
operations more frequently; in the second place, this high 
degree of sensitiveness exists only at the surface, so that 
such operations are less painful than we are accustomed 
to suppose—the bones, muscles, and other deep parts being 
very indifferently supplied with sensitive nerves; and in 
the third place, the medical art has furnished the means 
of suspending, temporarily, this sensitiveness. 
121. These nerves are not essential to merely animal 
life. They may be severed so that the individual will be 
insensible to any form of external injury, and not even 
know whether his limbs are connected with his body or 
not, except as he learns it by the sense of sight, while he 
may yet possess perfectly the power of motion, and while 
the appetite, digestion, and general health are unimpaired. 
Oases have occurred which justify these statements, and 
they have been proved by experiments on the lower 
animals.39 
3a There was a person in London, some years since, in whom on one 
side of the body the nerves of sensation alone were perfect, and on the 
other side the motor nerves, and those alone, were capable of performing 
their function. 
121. Are these nerves absolutely essential to animal life ? 102 
THE NERVES. 
122. There are some peculiar adaptations in these nerves 
to the kind of sensitiveness required. Thus, the exposed 
part of the eye is extremely sensitive to particles of dust, 
which, if allowed to collect, would soon destroy its trans- 
parency; but sensitiveness to violent injury would answer 
no good end, and accordingly hard pressure upon the eye 
—and even piercing it, in operation for cataract—is not 
very painful. In like manner, the muscles of the iris are 
sensitive only to light; nor are they sensitive to light 
thrown upon them, but to light admitted into the eye, the 
object being to graduate the quantity of light which the 
eye receives. In accordance with the same principle, the 
brain, which could receive no protection by a high degree 
of sensitiveness, is nearly insensible, so that considerable 
portions of it have been, in some cases, removed without 
producing pain. 
There is another adaptation seen in the sensitiveness 
varying with the need for it. The bones, cartilages, ten- 
dons, etc., have ordinarily but little sensitiveness, but when 
inflammation takes place in them they become painful in 
the extreme. It is only when they are in a diseased con- 
dition that susceptibility to pain could do us any good. 
Its severity is proportioned to the urgency of the case, for 
these deep-seated inflammations are always of a more 
serious character than the superficial ones. On the same 
principle any part becomes specially sensitive under in- 
flammation, in order to compel us to care for it while it 
needs care. 
Of a somewhat similar character is the relation of the 
nerves of sensation to those of motion, when under the 
122. Give instances in which the nerve, by the kind of sensation that it can 
convey, is adapted to the wants of the part to which it is distributed. Show how 
the variations of sensitiveness are an adaptation to the wants of the system. 
How are the different capabilities of the nerves of sensation and of motion to 
resist the effects of cold a provision for our protection f ■ THE HEEVES. 
103 
influence of intense cold. When any part is in danger 
of freezing, the sensitive nerves occasion severe pain, and 
we are thus admonished of our danger. But while the 
nerves of motion still retain their power, and there is, 
therefore, a possibility of making farther efforts to secure 
our safety, the sensitive nerves lose their power. The ces- 
sation of the pain frees us from the continuance of suf- 
fering, while by the change it again warns us that there is 
still a last chance of safety. 
123. (3.) The nerves of voluntary motion. Four 
pairs of the cranial nerves are connected with the volun- 
tary motions. The motor oculi, the trochlearis, and the 
abductor oculi govern the motions of the eye, and the 
hypoglossus governs the motions of the tongue. 
The anterior roots of the spinal nerves are the source 
of all the other voluntary motions of the system. Although 
there is this distinction of functions between the anterior 
and posterior roots of the spinal nerves, yet they sustain 
a most intimate relation to each other. The anterior roots 
are the means of communication between the organ of the 
mind and the muscles, by which motions are produced, 
while the posterior roots are the means of communication 
between the muscles and the organ of the mind. A com- 
mon form of expressing this relation is, that the nerves of 
motion carry the mandates of the will to the muscles, 
and the nerves of sensation convey back to the mind a 
knowledge of the condition of the muscle ; they inform the 
mind whether or not its mandates have been obeyed. 
Thus the circuit is completed when it commences at the 
brain. At other times it may be regarded as originating 
123. What is the third class of nerves ? What are the cranial nerves of this 
division, and what motions do they control ? What are the spinal nerves of vol- 
untary motion ? Describe the relation between the nerves of sensation and those 
of motion. 104 
THE NERVES. 
in some circumstance exterior to the body, a knowledge of 
which is conveyed to the mind by the nerves of general or 
special sensibility, and the mind controls the muscular ac- 
tion as the knowledge communicated may render desirable. 
124. (4.) The nerves of involuntary motion. 
The nerves which control the involuntary motions of the 
system are the facial portion of the seventh pair, the 
eighth pair, and the great sympathetic nerve. 
The facial nerve is the one upon which depends the expres- 
sion of emotions in the face, such as joy, grief, fear, anger, 
revenge, etc. These motions of expression may, by long 
practice, be brought, to some extent, under the control of 
the will, so that when the emotions exist they shall not 
be depicted in the face, or so that there may be expression 
of them in the face when the emotions do not exist.40 But 
40 It has, however, been said that some actors have obtained so complete 
control over this nerve, that they could not only give the expression of 
any emotion at pleasure, but that, to some extent, they could represent 
one class of emotions by one side of the face, and another class, at the 
same time, by the opposite side. 
The aborigines of this country have great power, not in giving the ex- 
pression of emotions which do not exist, but in suppressing the expression 
of emotions which they do feel. Hence the comparison, “ impassible as 
an Indian.” They are said to have cultivated this power from the desire 
to prevent Europeans from thus learning their wishes and taking advan- 
tage of them. 
The unwillingness which many persons feel to exhibit their emotions is 
not natural, and can scarcely be justified. This susceptibility was given 
us for wise purposes. Why should we be unwilling to show proper emo- 
tions ? and why should we not allow upon ourselves this check against 
124. WThat is the fourth class of nerves ? What nerves belong to this class ? 
What are the functions of the facial nerve ? To what extent may these motions 
become voluntary ? What easier way to avoid or exhibit the expression of emo- 
tions T What use do actors make of this fact ? What is the distribution and 
office of each nerve of the eighth pair ? To what extent is the great sympathetic 
connected with the other portions of the nervous system ? With what are its 
branches associated ? What is their distribution and office t THE XEJiVES. 
105 
this control is generally very imperfect. It is much easier 
to control the emotions than to control the natural ex- 
pression of them when they arise. Hence it is that actors 
strive to awaken the emotions in their own mind which 
they wish to represent, and allow the natural expression 
of them in the countenance, rather than attempt to give 
the expression of them when they do not exist. 
The three parts of the eighth pair of nerves have sepa- 
rate functions. The glosso-pharyngeal directs the motions 
of deglutition ; the par vagum seems to act in conjunction 
with the great sympathetic; and the spinal accessory di- 
rects those involuntary motions of the neck and shoulders 
which take place in coughing or sneezing. 
We have seen that the great sympathetic is intimately 
associated with the other portions of the nervous system 
by numerous filaments It, however, seems to be, to a 
great extent, a system of independent nervous influence. 
The nerves which it gives off become associated with the 
branches of the par vagum, and together they form sheaths 
of nervous matter around the arteries; they also collect in 
plexuses on the heart, the diaphragm, the stomach, the 
kidneys, etc., to all which organs they supply the requisite 
nervous influence.41 
improper emotions ? This involuntary manifestation of emotions is one 
of the most pleasing elements of social life, while it is also a safeguard 
against injury, because it is the natural warning which excited passion 
always gives. We are most charmed by those whose emotions are strongly 
painted in the face, but we are always suspicious of the person who can 
keep his emotions to himself. 
41 A fifth class of nerves is generally introduced, which preside over the 
respiratory movements. As this motion is both voluntary and involun- 
tary, it is supplied with both kinds of nerves. The involuntary are always 
active, yet the voluntary nerves can, for a short time, control their action. 
Sir Charles Bell, who first proposed this as a distinct division, also no- 
ticed a peculiarity in the origin of these nerves, namely, that they take 106 
THE SENSE OE SIGHT. 
CHAPTER II.—OF THE ORGANS OF THE SENSES, 
Section I.—The Sense of Sight. 
125. The structure of the organ of sight may be con- 
sidered in reference to its external and internal parts. 
1st, the external parts. The orbit of the eye is a 
deep cavity, situated in the upper part of the face and 
directly under the anterior lobe of the brain. The ball 
of the eye is lodged in the orbit, but does not entirely fill 
it. The space between the ball and the orbit is filled with 
muscles and adipose substance. The muscles and their 
action have been elsewhere described. The adipose sub- 
stance serves to fill up the irregularities of the orbit and 
as a cushion for the ball. 
The front part of the eye, so much as can be seen by 
lifting the lid, is covered by a very delicate membrane, the 
conjunctiva, which possesses extreme sensibility to the 
presence of minute foreign particles upon the surface, and 
is therefore an important protection to the eye in main- 
taining its transparency. The eye is farther protected by 
the lids, at the edges of which, as a curtain, are attached 
cartilages, which keep the lids in form, and serve for the 
attachment of the muscles to open and close them. 
their rise in the upper part of the spinal cord from a lateral portion, in- 
termediate between the voluntary and involuntary portions of the cord, as 
if the two had here blended into a common tract, for the purpose of giving 
to the nerves from this portion this double character. 
Chapter II. Section I,—125. What are the external parts of the eye f 
Describe the orbit. What besides the ball of the eye does it contain ? Describe 
the muscles of the eye. (See Appendix.) What is the conjunctiva ? What is its 
office ? Describe the eyelids. By what muscle is the upper lid raised ? By what 
muscle is the eye closed ? Describe the lac hrymal eland. How is the lachrymal 
secreiion useful ? How is it disposed of ? What circumstances tend to mciease 
this secretion t THE SENSE OF SIGHT- 
107 
The lachrymal gland (1, Fig. 71), about the size of an 
almond, lies in the upper outer part of the orbit, and fur- 
nishes, by several ducts (3), a fluid 
secretion which is spread over 
the eye every few seconds by the 
motion of the lids. Its object is 
to prevent friction by the motion 
of the lid, to keep the surface 
moist, and to wash off whatever 
may have fallen upon it. This 
fluid collects finally at the inner 
corner of the eye, and is taken 
up by two capillary tubes, the 
puncta lachrymalia (3, 3), and 
by them conveyed to the lachry- 
mal duct (4), and is thence dis- 
charged into the nose.43 The 
current of air passing through the nostrils will generally 
cause the evaporation of whatever moisture is thus thrown 
into the nose. In a diseased condition of the eye, or from 
particular states of mind,43 this secretion may be increased 
till the current of air does not take it up, or even so much 
that it escapes as tears outside of the eye. 
Fig. 71. 
1 The lachrymal gland. 2 The 
ducts by which its secretions are 
conveyed to the eye. 3, 3 The 
puncta lachrymalia. 4 The lach- 
rymal duct. 
126. 2d. The internal parts of the eye. The ball 
41 The lachrymal duct is lined with a continuation of the membrane of 
the nose, and in case of colds, this membrane is liable to become thickened 
so much as to fill the duct. When it becomes permanently filled, a small 
metallic tube may be inserted, and is found to answer the purpose perfectly. 
When this is not done the eye becomes inflamed, and the sight is in danger 
of being lost. 
43 This secretion is increased when any extraneous matter gets into the 
eye, for the purpose of washing it out. Why it should be increased by 
mental emotions we do not know, yet such is the fact, and it is certain that, 
in some way, it does tend to mitigate the crushing influence of deep grief. 
126. What is the shape of the eye-ball ? By.how many layers or coats is the 108 
THE SEtfSE OF SIGHT. 
of the eye is nearly a perfect sphere, with the exception 
of the protuberant part (2, Fig. 72) in front, which is a 
Fig. 72 
Section of the Eye. 1 The sclerotic coat. 2 The copiea. 3 The choroid coat. 
6, 6 The iris. 7 The pnpii. 8 The retina. 9 The ciliary processes fi'om the 
choroid coat by which the crystalline lens is supported. 10 The anterior cham- 
ber of the eye. 11 The posterior chamber. 12 The crystalline lens. 13 The 
vitreous humor. 15 The optic nerve. 16 The artery of the interior of the eye. 
small segment of a smaller sphere than the body of the 
ball. The ball is supported in its form by several mem- 
braneous layers. 
The outermost is the sclerotica (1), a dense, opaque 
membrane, commonly referred to as the “ white of the 
eye,” which forms an entire envelope for the eye, except 
a circle of about half an inch diameter in front. This 
space, the protuberant part of the eye, is covered by ano- 
ther membrane, the cornea, which may be regarded as 
a continuation of the sclerotica, and which differs from it 
principally'in being transparent. The iris (6) is a small 
membrane attached to the anterior edge of the sclerotica. 
eye surrounded ? Describe the sclerotica. The cornea. Describe the iris. 
What is the pupil ? What is the second coat of the eye ? In what state is the 
interior of this coat ? What is the use of this pigment ? What is the third coat 
of the eye ? Describe the retina. THE SENSE OF SIGHT. 
109 
The circular orifice (7) in the centre is the pupil. The 
iris is composed of circular and radiant muscular fibres 
(Fig. 73) by which the pupil may be en- 
larged or contracted, so as to increase or 
diminish the amount of light admitted 
into the eye. 
Fig. 73. 
The second envelope is the choroid 
coat. It is within the sclerotica, in con- 
tact with it, and is terminated in front 
by a thickened edge called the ciliary 
ring. The interior of the choroid coat 
is covered by a black or very dark pig- 
ment, the use of which is to absorb any 
light which might otherwise be diffused through the eye.44 
A view of the iris, 
showing the circu- 
lar muscular fibres 
around the pupil, 
and the radiating 
fibres reaching to 
the circumference. 
The innermost layer is the retina. It is formed by 
the optic nerve, which, after it passes into the eye, is 
spread out into a thin, delicate network, lining the whole 
interior of the eye, and is the seat of vision. 
Fig. 74. 
A Any point of a variable object from which rays come into the eye through the 
pupil, 1. 1, are converged principally by the lens 2, 2, and brought to a focus on 
the retina at 4. 3, 3 The vitreous humor. 
44 In imitation of this peculiarity of the eye, and to accomplish the same 
object, it is the uniform practice to blacken the inside of telescopes and 
other optical instruments. 110 
THE SENSE OF SIGHT. 
127. The eye is filled by three transparent substances, 
the object of which is to concentrate the rays of light 
which enter the eye. The vitreous humor (3, 3, Fig. 
74) is in the posterior part of the ball, and occupies about 
four-fifths of its cavity. It is very similar in appearance 
to the white of an egg, but it is more viscid. The aque- 
ous humor is a perfectly limpid liquid, situated in the 
front part of the ball. The iris is suspended in this hu- 
mor, and divides it into anterior and posterior chambers 
(10, 11 Fig. 72). The crystalline body (12) is a solid 
double-convex lens, situated between the aqueous and vit- 
reous humors, and is suspended in its position by fila- 
ments from the ciliary ring. This lens increases in density 
from the circumference to the centre, and the convexity 
of the posterior is greater than that of the anterior face. 
128. Light is the only appropriate stimulus of the 
nerves of sight. If we consider separately the rays which 
come from a single point of a visible object, we shall see 
that they are necessarily divergent. Those which enter 
the eye we may regard as forming a cone, of which the 
point of origin (A, Fig. 74) is the apex, and the area of the 
pupil (1, 1) is the base. The object of the refracting me- 
dia46 of the eye is to bring all the rays of this cone to a 
point at 4. The cornea first acts upon the rays to diminish 
their divergence. The aqueous humor slightly increases 
this divergence, but not enough to overcome the effect of 
the cornea. In this state those rays which pass through 
46 This is not the place to discuss the properties of light, and we must 
assume that the general laws of the refraction of light are understood. 
127. With what are these coats tilled? Describe the vitreous humor. The 
aqueous humor. How is it divided ? Describe the crystalline lens. 
128. What is the physical agent in producing vision ? Why are the rays of 
light divergent as they enter the eye ? What is the object of the refracting me- 
dia of the eye ? What is the effect of each portion, and what is the final effect ? 
When the rays of light are brought to a locus on the retina, what is the effect ? THE SEXSE OF SIGHT. 
the pupil and fall upon the crystalline lens (2, 2) are made 
to converge, and the convergence is so far increased by 
the vitreous humor (3, 3), that when they reach the retina 
they all fall upon the same point (4). The retina, which 
is an expansion of the optic nerve, and in which this point 
is situated, communicating directly with the brain, the 
sensation of sight at once exists in the mind. How the 
focus of light on the retina produces sensation we can form 
no idea whatever; we must receive it as an ultimate fact.48 
It is a 'primary laic of vision that any point of a visible 
object is seen in the direction of a straight line from its 
focus (4, Fig. 74) on the retina, through the centre (5) of 
the pupil. All the points of a visible object from which 
light can reach the eye will be represented by correspond- 
ing points in the eye; and these points on the retina, 
which, taken together,' constitute a perfect image of the 
object, will, when seen together, convey to the mind a dis- 
tinct idea of the object. 
It is the object of this sense to convey directly only 
ideas of the color of objects and their direction from us, 
and of solidity; but indirectly it becomes the most impor- 
46 It is important to fix in the mind, that we can form no idea how sen- 
sations are produced. We can trace the successive changes up to the 
brain, but we find nothing which would lead us to expect the result. 
When we examine the result, we see no reason why it should have been 
produced by the light, nor why light should be necessary. The study of 
nature, in every department, is continually bringing us to these limits of 
human power, compelling us to feel that these are not only unexplained 
facts, but are, in their nature, inexplicable to beings of our limited capaci- 
ties, and leading us to recognize, in all our investigations, the existence 
everywhere of an efficient Cause, which can be only God. 
How does it produce this effect ? What is the direction in which a visible point 
is se n ? If we see only points, how do we see any object ? What ideas does 
the seuee of sight give us directly f What does it give indirectly ? 112 
THE SENSE OF SIGHT. 
tant of the senses, by giving us the ideas of form, magni- 
tude, distance, and motion. 
129. It is obvious that the highest points of an object 
(A, Fig. 75) will be represented on the retina by the low- 
Fig. 75. 
A and B Two points of a visible object. The pencil of rays from each point is 
brought to a separate and perfect focus on the retina, and each point is seen in 
the direction from a or b through the centre of the pupil. 
est points, h, and the lowest points of the object by the 
highest points on the retina—that is, the pencils of light 
will cross at the pupil, and the image will be inverted. 
But the mind does not see the image any more than it 
does the object. Each point in the retina upon which the 
image is placed conveys to the mind an idea of its true 
position as referred to the object. The point h is recog- 
nized to be at A, in accordance with the general law above 
given; the point a at B, and so of every other point; 
that is, objects are seen erect, and not inverted. 
130. Each point in one retina has a corresponding point 
in the other, and these two points sustain by our nature 
such a relation to each other, that when they are both 
129. Why will the image in the eye be inverted ? Why then is not the object 
seen inverted ? 
130. Why do we see objects single with two eyes ? How may the eye be so 
affected that we shall see two objects when there is but one t THE SENSE OF SIGHT. 
113 
acted on exactly alike, that is, by the same object, they 
convey to the mind the impression of but one object; but 
if, by a slight pressure of one eye from its natural posi- 
tion, we cause the same object to be represented on parts 
of the retina which are not corresponding parts, we see 
two objects, though there is but one. We, therefore, see 
objects single, though seen by both eyes, because they 
affect corresponding parts in both retinas. 
131. As the refraction of a ray of light depends in part 
on the degree of obliquity with which it falls on the re- 
fracting substance, it will be seen that the outermost rays 
(D D, Fig. 76) which come from a visible object, as they 
Fig. 76. 
The ray A O passing: through the centre of the lens is not refracted at all The 
rays B B are refracted somewhat, and come together at o. C C meet at h and 
D D are the most refracted, and come to a focus at n. 
fall upon the lens more obliquely, will be most refracted. 
If the lens be of uniform density and have a spherical 
curve, the outer rays will be brought to a focus at n, 
nearer to the lens than those rays which are more central. 
131. What is spherical aberration ? Ilow is it corrected in the eye ? 114 
THE SENSE OF SIGHT. 
This is called spherical aberration. To obviate it 
and bring the focus of all the rays at h, the crystalline 
lens is more dense toward the centre, in order to increase 
its refracting power upon the more central rays. Besides, 
the iris cuts off the extreme rays, and allows only those 
near the centre to enter the lens.47 
132. There are two circumstances in connection with 
vision which are subject to constant variation, namely, the 
distance of the object and the intensity of the light; and 
the eye has the power of adapting itself to these variations. 
The amount of light admitted is controlled by the iris. 
After being in a full light for a short time, the pupil be- 
comes so small by the contraction of its circular fibres, 
that upon entering a partially closed room wTe seem to be 
in utter darkness, so little light does the pupil admit. 
But very soon the rad’ant fibres of the iris contract, the 
pupil enlarges, and enough light is received into the eye 
to give us distinct vision, though the light of the room 
remains the same. The object o' the iris is to guard the 
retina from injury by exposure to too intense a light, and 
hence the muscles of the iris arc not directly sensitive to 
light. It has been proved, by careful experiment, that 
light thrown upon the iris has no effect to contract the 
47 An adjustment is also necessary to prevent the effects of ehromat’c 
aberration ; that is, to prevent the image on the retina being colored, in 
consequence of the different degrees of refrangibility of rays of light of 
different colors. This explanation requires a somewhat intimate acquaint- 
ance with optical principles. The eye is probably not absolutely achro- 
matic. Whatever correction for this aberration is made, is due to the pe- 
culiar combination of solid and fluid lenses in the eye. 
132. What are the two varying circumstances to which the eye must adapt 
itself ? How is the amount of light controlled ? Does strong or weak light, con- 
trol the action of the muscular fibres of the iris as it falls unon them ? How is 
this action controlled ? Why should the size of the pupil be controlled by the 
retina ? THE SENSE OF SIGHT. 
115 
circular musoles, and the contraction of the radiant mus- 
cles is not promoted by screening them from the light. It 
is the retina itself which, in some unexplained way, reacts 
upon the iris to effect the contraction and relaxation of its 
muscles. Thus the control of these muscles is given to 
the part which they are designed to protect. 
133. If rays of light come from two points (a and b, 
Fig. 77) it is obvious that those which come from the 
Fig. 77. 
The rays from b which fall upon the lens A A, are necessarily less divergent than 
those from the nearer point a. As they diverge less, they will require less 
bending to bring them to a focus, or by the same bending they will come to a 
focus b' nearer to the lens than a', the focus of rays from a. 
greater distance, b, will have less divergence, and will, 
therefore, come to a focus (at b') nearer the lens than 
those which have greater divergence. In order that this 
more distant object be distinctly seen, the retina might be 
brought forward from a' to V ; or the refracting power of 
the lens might be diminished so as to keep the focus still 
at a'. The latter method seems to be adopted. The crys- 
talline lens, in its ordinary condition, is compressed by the 
ciliary processes, as a band around its circumference, and 
its front is bulged out so that it can sufficiently converge 
the rays from near objects. When a distant object is 
looked at, muscular fibres extending from 11, Fig. 72, to 
the edge of the choroid act on the band of ciliary pro- 
133. Why is an adjustment necessary to see objects distinctly at different dis- 
tances ? How is this adjustment made ? 116 
THE SENSE OF SIGHT. 
cesses, drawing it slightly away from the lens, which then 
takes its uncompressed form and becomes flattened; that 
is, it loses a part of its converging power, just enough so 
that the less divergent rays from distant objects will come 
to a focus on the retina. Thus the eye is adapted to dis- 
tinct vision at varying distances. 
131. When both eyes see the same solid object, the right 
eye must see more of it on the right side, and the left 
eye more of it on the left side, and yet we are conscious 
of only one object, but we are conscious of it as a solid. 
The stereoscope is an optical instrument so constructed 
that we may see at the same time two pictures of a solid 
body, not exactly alike, but differing from each other just 
as the images do on the two retinas. The two pictures 
give us the conception of only one object, but it is not 
the conception of a picture; that is, it is not the concep- 
tion of a plane surface, but of a solid body. It seems, 
then, that we are constituted so as to get, by the use of 
two eyes, the notion of body, or solidity. 
135. There are persons in whose eyes the retina is natu- 
rally so far from the lens that only those objects can be 
distinctly seen that are very near: there are others in which 
48 Another peculiarity of the eye is, that the retina retains for a very 
short time the impressions which it receives—not long enough to prevent 
other impressions from being received almost immediately, but yet enough 
so that a rapidly moving point gives us the conception of a line. If 
the impression on the retina were effaced instantly on the discontinuance 
of the ray of light, we should he left for a moment in the dark every time 
the light is intercepted by winking. 
134. How do the images of the same solid body on the two retinas differ ? 
What knowledge does this difference of the image convey to us ? How is this 
illustrated by the stereoscope ? 
135. What is the form of the eye in short-sighted persons 1 To remedy this 
defect, what change must be made in the direction of the rays coming from dis- 
tant objects ? How is this change effected ? What is the peculiarity of the 
in long-sightedness ? What glasses are required, and why ? THE SENSE OF SIGHT. 
117 
the retina is naturally so near the lens that only very dis- 
tant objects are distinctly seen. In the first case, that of 
short-sightedness, it is necessary to increase the diver- 
gence of the rays ; hence concave glasses (Fig. 78) must be 
Fig. 87. 
A cone of rays rendered more divergent by a concave lens, a a, to remedy short- 
sightedness. The rays from a distant object, b, enter the eye with the same 
degree of divergence by the aid of the lens that they would if. without the 
lens, they came from c. If the eye is adapted to see distinctly an object at c 
without the lens, it must also be adapted to distinctly see an object at b with 
the use of the lens. 
used. In case of long-sightedness, it is necessary to 
diminish the divergence when near objects are looked at, 
and therefore convex glasses (Fig. 79) are required. 
Fig. 79. 
A cone of rays rendered less divergent by a convex lens, a a, to remedy long 
sightedness. The rays from a nearer object, &, enter the eye with the same 
divergence, by the aid of the lens, a (i, that they would if, without the lens, 
they came from c. The eye cau see distinctly the more distant object, c, with- 
out the lens. It must then be able to see distinctly the nearer object, 6, by the 
use of the lens, because the rays enter the eye as if they came from c. 
136. There is sometimes an imperfection in some of the 
appendages of the eye, by which they cannot move in such 
a way that the corresponding parts of the two retinas 
136. In what does squinting consist, and how can it be remedied ? In what 
does looking cross-eyed consist, and how is it to be remedied f Do these defects 
of the eye produce double vision f 118 
THE SENSE OF SIGHT. 
shall be affected by the same object. Sometimes one eye 
is weaker than the other, and we insensibly turn it toward 
the inner angle to reduce the amount of light received. 
The first of these is squinting, and the last is cross-eye. 
In both cases there is double vision ; the two eyes convey 
different impressions of the same object. The mind, how- 
ever, soon accustoms itself to attend to but one of the 
impressions. By shading the eye and directing attention 
to its motions, cross-eye may easily be cured. Squinting 
can be cured only by a surgical operation, and this is not 
always successful. 
137. The sight is improved by practice, like every other 
organ, but it requires care. There is no other organ more 
likely to be overtasked. This may be by using it too con- 
tinuously without rest, or with too strong or too weak a 
light. Beading at twilight is a very common way of in- 
flicting injury upon the eye. The evil first appears as a 
slight inflammation. If the cause of injury is removed 
and rest is allowed, it may generally be cured by frequent 
bathing of the eye in pure water, as cold as it will bear 
without pain. Any other eye-waters are generally inju- 
rious, and should never be used, unless prescribed by a 
judicious physician. 
The eye is also apt to sympathize with a disordered con- 
dition of the general health. When this is the case the 
health and not the eyes requires attention. 
137. How is the eye liable to injury ? How should the eye under such circum- 
stances be treated ? How does the general health affect the eye f How should 
the eye then be treated ? THE SENSE OF HEAEING. 
119 
Section If.—The Sense of Hearing. 
138. The organ of hearing consists of the external ear, 
the ear tube, the tympanum, and the labyrinth. The ex- 
ternal ear (1, Tig. 80) is a cartilaginous substance, 
Fig. 80. 
The Ear. 1 The external ear. 2 The ear tube. 3 The membrana tympani. 4 
The tympanum. 5 The vestibule. 6 The cochlea. 7 The semicircular canals. 
8 The* auditory nerve. 9 The Eustachian tube. 
situated around the orifice of the ear tube. It is probably 
useful to some extent in collecting the vibrations of the 
air and directing them toward the internal ear. Yet, in 
cases where the external ear has been destroyed or want- 
ing, the delicacy of hearing seems not to be sensibly di- 
minished. In the lower animals the form of the ear is 
more distinctly funnel-shaped, and is movable at pleasure, 
Section II.—138. Of what does the organ of hearing consist? Describe the 
external ear. How do the lower animals differ from man in the form and use of 
the external ear T 120 
THE SENSE OE HEARING. 
so that it may be directed toward the object from which 
sounds come. There are muscles suitably situated for 
giving these motions to the human ear, but, either from 
neglect or otherwise, these muscles are not under the con- 
trol of the will. 
139. The ear tube (2) is a cylindrical cavity extend- 
ing about an inch inward from the external ear. It is 
lined with a membrane continuous with the external skin, 
and in this membrane are situated numerous follicles 
from which the ear-wax is secreted. 
140. The tympanum (4) is a continuation of the ear 
tube for about a third of an inch, and is separated from 
it by a thin membranous partition (3), the memhrana tym- 
pani. The cavity of the tympanum has, therefore, no 
communication with the external air through the ear tube, 
but there is a long, funnel-shaped tube (9) proceeding from 
the upper and back part of the throat and opening into 
the tympanum. This is the Eustachian tube, and 
serves to keep the air of the same tension on both sides of 
the membrana tympani. The tympanum communicates 
with the labyrinth by two small openings in the bone, of 
which the upper one is called the fenestra ovalis, and the 
rig. 81. 
The Bones of the Ear. 1 The malleus. 2 The incus. Just below the incus is 
the small orbicular bone. 3 The stapes. 
139. Describe the ear tube. 
140. The tympanum. The Eustachian tube. How is the tympanum sepa- 
rated from the ear tube f How are the tympanum and labyrinth connected ? 
How does the membrana tympani connect with the fenestra ovalis ? THE SENSE OF HEARING. 
121 
lower one is the fenestra rotunda. These windows are 
closed by an extension over them of the common lining 
membrane of the ear. Within the tympanum are four 
small hones (seen separately in Fig. 81), the relative posi- 
tions of which are seen in Fig. 82. The first (the malleus) 
Fig. 82. 
An ideal representation of the principal parts of the Ear. A The ear tube, sepa- 
rated by a membrane from B, the tympanum, abed The small bones of the 
tympanum, a Rests against the membrana tympani, and its position maybe 
slightly changed by the muscle/, d Rests against the membrane 2 of the fenes- 
tra ovalis. 3 Is the fenestra rotunda. C May be taken to represent generally 
the labyrinth, and D, the membranous labyrinth, both filled with the liquor of 
Cotunnius. 122 
THE SENSE OF HEARING. 
is placed against the inner surface of the membrana tym- 
pani, and the other two (the incus and os orbiculare) con- 
tinue the connection to the last (the stapes), which is 
placed against the membrane of the fenestra ovalis. They 
are so arranged as to form a compound lever, and so con- 
nected with muscles (of which muscle /, Fig. 82, is this 
most important) that the two extremities of the lever are 
exactly fitted at all times to their respective membranes. 
141. The labyrinth consists of the vestibule, the cocnlea, 
and the semicircular canals. The vestibule (5, Fig, 80) 
is a cavity about equal in size to a grain of wheat, and 
situated immediately beyond the fenestra ovalis. The an- 
terior part of the labyrinth is the cochlea (6). It is of 
a pyramidal form, and resembles a snail shell. Its spiral 
hollow makes two and a half revolutions, and is separated 
throughout its whole extent, except at its apex, by a lamina 
of bone. One division of the spiral terminates at the 
fenestra rotunda, and the other opens into the vestibule. 
The posterior part of the labyrinth consists of the semi- 
circular canals (7), which are three bent tubes, the planes 
of which are situated at right angles to each other, and 
which open into the vestibule. These parts, lined writh a 
delicate membrane, constitute the osseous labyrinth. 
Besides this, there is a membranous labyrinth, of the 
same form as the osseous (with the exception of the coch- 
lea), and lying within it. The parts of the labyrinth 
highly magnified, are seen in Fig. 83. The general rela- 
tions of the several parts of the ear (but not the form) 
will be gathered most readily from Fig. 82. 
142. The auditory nerve (8, Fig. 80), which is a por- 
141. Of what does the labyrinth consist? Describe the vestibule. The 
cochlea. The semicircular canals. The membranous labyrinth. 
142. Give the distribution of the auditory nerve. What is the object of the 
lining membrane of the labyrinth ? THE SENSE OF HEARING. 
123 
Fig. 83. 
The labyrinth distinct, from the hone in which it is situated, and highly magnified. 
1 The cochlea. .3, .3 The spiral tubes of the cochlea. 2. 2 The lamina of bone 
by which they are separated. 7 The vestibule. 8 The fenestra rotunda. 9 The 
fenestra ovalis. 11,12, 13 The semicircular canals. 
tion of the seventh cranial pair, is distributed over the 
interior of the membranous labyrinth, and over both sur- 
faces of the lamina by which the cochlea is divided. The 
cavities of both labyrinths are filled with a limpid, trans- 
parent liquid, secreted from the surface of the lining mem- 
brane, and called the liquor of Cotunnius. Thus both 
sides of the substance over which the nerve is spread are 
bathed in this liquid. 
143. The vibrations of the air enter the ear tube, and 
reach the membrana tympani. The motions which it re- 
ceives are transmitted, by the system of bones within the 
tympanum, to the membrane of the fenestra ovalis. The 
143. Describe the course of the vibrations of the air till they reach the nerve. 
If the membrana tympani were destroyed, how would the vibrations reach the 
nerve ? How is the sensation of hearing produced ? 124 
THE SENSE OF HEARING. 
same motions are also transmitted by the air within the 
tympanum to the membrane of the fenestra rotunda. Thus 
the two membranes which connect with the labyrinth are 
acted upon by the vibrations of the air, and communicate 
those vibrations to the liquid of the labyrinth, in which 
the nerves of hearing terminate. 
Thus far we can trace the physical causes upon which 
hearing depends. We know that these nerves must be 
compressed by each vibration, that they extend to the 
brain, and that the immediate consequence is hearing. 
But why this compression of the nerve should be followed 
by sensation, and this sensation be hearing, is entirely 
unknown. 
144. These vibrations of the air are produced by the 
vibrations of some solid substance. Thus, if the string of 
a musical instrument be drawn aside from a right line, 
and left to its own tension, it will not only return to a 
right line, but the velocity acquired will carry it nearly as 
far to the opposite side as it had at first been drawn from 
its natural position. This oscillation will continue for some 
time, and will communicate a vibratory motion to the air. 
The same vibrations may be communicated in various 
ways, as by a bell, the prongs of a tuning-fork, the springs 
of an accordeon, or the vocal cords of the larynx, etc. It 
is these atmospheric vibrations48 which are transmitted to 
49 Whatever will facilitate the transmission of these vibrations, will assist 
the hearing. Thus, a speaking-trumpet enables the speaker to give greater 
force to the vibrations in a particular direction. In a large room where 
many persons are talking, or when machinery is in operation, the voice is 
scarcely audible, the vibrations are so much interfered with. But by 
speaking through a continuous tube the voice may be sent to various 
parts of a building, and be heard distinctly. 
144. How are the vibrations of the air produced ? How is it proved that the 
air is the medium of transmission ? THE SENSE OF HEARING. 
the auditory nerve, and convey the sensation of sound; 
for if the vibrations of any sonorous body, as of a bell, be 
produced in a bell-glass, from which the air has been ex- 
hausted, no sound will be perceived. 
145. It is, however, not essential that the medium of 
communicating them should be the air. Solid substances 
are good conductors. The tick of a watch held in the 
mouth will be scarcely heard till it is allowed to touch 
the teeth, when the sound will become distinct. The 
earth, ice, and even water, are good conductors of sound.60 
146. Many attempts have been made to ascertain what 
special purpose is accomplished by each part of the laby- 
rinth. There seems to be some reason for regarding the 
cochlea as the mechanism by which we recognize musical 
sounds. The functions of the other parts have not been 
definitely ascertained.61 
50 It is said that the discharges of cannon at the battle of Banker’s Hill 
were heard at the distance of a hundred miles by placing the ear to the 
ground. The Indians of the prairies are in the habit of applying their ear 
to the ground to ascertain whether droves of wild horses are approaching. 
The conducting power of solids can be well shown by applying the ear to 
one end of a long stick of timber, and letting the other end be slightly 
scratched with a pin ; a very feeble sound will be transmitted a hundred 
feet, and seem to be scarcely diminished. A person will be convinced of 
the conduction of sound by water if he will put his head under water, and 
strike two stones together; the sound is much greater than in the open 
air. 
61 The intensity of sound it is thought that we judge of by the tympa- 
num, the musical note by the cochlea, and the quality of sound by the 
semicircular canals—meaning by quality that peculiarity by which we dis- 
tinguish persons by their voices or two musical instruments from each other, 
though the loudness and the musical note be the same. 
145. What other substances besides the atmosphere will act as conductors of 
vibrations ? 
146. What are the functions of the several parts of the labyrinth ? 126 
THE SEJSTSE OF HEARING. 
147. In order that this sense be perfect, the whole ap- 
paratus in a perfect state is required ; and yet the external 
ear may be lost and hearing still remain ; the membrana 
tympani may be broken, and the vibrations may still reach 
the nerve through the air which is in contact with the 
membrane of the fenestra rotunda; and even when all 
these means are taken away the nerve may be, to some 
extent, affected by vibrations communicated to it through 
the bones of the head. But when the nerve itself is in- 
jured, hearing is impossible. Hearing is quite destroyed 
also by the absence of the liquid in the labyrinth. 
148. There are, however, several ways by which hearing 
may be more or less interfered with. The membranes 
may become rigid or thickened, and can be restored only 
by a generally improved condition of the system. The 
secretion in the ear tube may be excessive and fill the tube, 
or it may harden on the membrana tympani. This can 
generally be relieved by softening the secretion with a few 
drops of sweet-oil in the ear, and after an hour or two 
syringing the ear with soap and warm water. If this treat- 
ment does not in a short time give relief, it is because the 
deafness depends upon other causes, and no external ap- 
plication can avail. Deafness may arise from a closure 
of the Eustachian tube; as the lining of this tube is the 
same membrane that lines the nasal cavities, a cold, that 
is, an inflammation of this membrane, is very likely to in- 
crease its thickness so as to fill the tube. In such cases the 
deafness will generally subside with the inflammation. 
When the tube becomes closed by the permanent enlarge- 
ment of the tonsils, it is necessary for the deafness as well 
as for the general health that they should be removed. 
147. How much of this apparatus is essential to hearing ? What parts may 
be lost without destroying the sense ? 
148. What are among the ordinary causes of deafness? How is each to be 
treated ? THE SENSE OF SMELLING. 
127 
The ear becomes exceedingly painful in consequence of 
such a degree of inflammation in the ear tube as to bring 
on ulceration. The inflammation should always be checked, 
if possible, in an earlier stage by cold applications, or, if 
necessary, by local bleeding, such as cupping or leeches. 
Section III.—The Sense of Smelling. 
149. This sense has its seat in the surface of the outer 
part of the air passages to the lungs ; and it seems to de- 
pend for its acuteness upon the amount of surface over 
which the nerve is spread. In order to increase this sur- 
face, in the first place, there are three thin sheets of bone 
(the turbinated bones) which lie partly rolled up within 
each nasal cavity (1, 2, 3, Fig. 84). In the second place, 
Fig. 84. 
A vertical section of the hones of the face a little forward of the ears. 1,1 Lower 
spongy bones. 2, 2 The middle spongy bones. 3, 3 Superior spongy bones. 
4 Antrum maxillare. 
there are several cavities in the bones of the head and 
face, not otherwise employed, which are made to commu- 
Sertion III.—149. Upon what docs the acuteness of this sense depend? 
How are nasal surfaces increased ? 128 
THE SENSE OF SMELLING. 
nicate with the nasal passages and form part of the nasal 
surfaces. Two of these are the antra maxillaria and the 
frontal sinuses. 
150. Over all these surfaces is spread the Schneide- 
rian membrane, the object of which is to deposit a 
mucous secretion, by which, in a healthy state, they are 
continually moistened. 
151. The olfactory nerve enters the nasal cavities 
through the sieve-like apertures in the ethmoid bone, and 
branches are distributed by division and subdivision over 
every part of this membrane. 
152. It has been doubted whether odors consist of mate- 
rial particles emanating from odoriferous bodies ; whether, 
for instance, material particles escape from the rose to dif- 
fuse its odor; for, in the first place, the continual escape 
of odors does not seem to diminish its substance, and, in 
the second place, analyses do not detect the chemical par- 
ticles of which its odors consist. In many other cases, 
however, they are known to be material, and it is presumed 
they always are. But, whatever be their nature, these 
odors, diffused through the atmosphere, are drawn into the 
nose, and coming in contact with filaments of the olfac- 
tory nerve, the impression of them is conveyed by the 
nerve to the brain, and the sensation of smelling is the 
result. 
153. It has been noticed that the nasal surfaces consti- 
tute the sides of the usual air passages to the lungs, so 
that the same muscular effort which is expended in res- 
piration causes a current of external air, with whatever 
150. How are these surfaces covered? 
151. What is the distribution of the olfactory nerve ? 
152. Describe the process by which smelling is produced. 
153. What are the advantages of making the air passages and the nasal cavi- 
ties the same ? How is the air made to come in close contact with the nac-al 
surfaces ? How do we voluntarily increase the effect of odors ? THE SENSE OF SMELLING. 
129 
odors it may contain, to pass oyer these surfaces and come 
in contact with these nerves. It is also to be observed 
that the turbinated bones, while they increase the surface 
over which the olfactory nerves are spread, partially fill up 
the spaces, so as to require the air in passing to come more 
in contact with the surfaces thus increased. And when- 
ever we wish to stimulate this sense to the utmost, we 
voluntarily compress as much as possible the air passages, 
and cause the current of air to strike upon them with 
considerable force. 
154. This sense may be useful, to some extent, in assist- 
ing us to discriminate between useful and hurtful food. 
Possibly it is useful in removing from the air some ele- 
ments which, if taken into the lungs, might be hurtful. 
It is unquestionably serviceable as a warning against 
noxious vapors. And yet it seems to he the sense least 
essential to our existence, and having, more than any other 
sense, for its special object simply to increase the enjoy- 
ments of life. 
155. The Schneiderian membrane is so situated as to 
be, perhaps, the most exposed of any part of the system 
to variations of temperature ; and these changes often pro- 
duce the inflammation and secretion which we speak of as 
a cold in the head. But this membrane is also always 
liable to indirect disease, by taking on the extra labor of 
the system when the excretions have been checked in other 
parts. Hence, a cold is likely to show itself in the nasal 
cavities first, and the excessive secretion indicates not so 
much a disease of that membrane as of suppressed action 
elsewhere, generally of the external surface. 
154. How is this sense useful ? 
15 5. What is a direct cause of disease in this membrane ? What is indirectly 
the cause of diseased action ? 130 
THE SEKSE OF TASTIKG. 
Section IV.—The Sense of Tasting. 
156. This sense has its seat in the tongue, and, to some 
extent, in all parts of the mouth. The tongue is covered 
with fine filaments called papilla, which give it a velvety 
appearance. On the edges of the tongue there are also 
other papillae, of larger size, conical form, and brighter 
color. These papillae, of both kinds, but particularly the 
larger ones, contain the terminations of the lingual branch 
of the fifth pair of cranial nerves. 
157. Substances which are capable of solution and of 
being tasted are called sapid substances. When the saliva 
containing such substances in solution flows around these 
papillae, the impression which they make upon the nerve 
within is communicated to the brain, and the sensation 
of tasting is produced. 
158. When substances which produce an agreeable taste 
are placed in the mouth, there is an increased secretion 
of the saliva52 to facilitate the solution of it and promote 
the gratification of this sense. The taste is also rendered 
more acute by pressing the tongue against the roof of the 
mouth, and thus bringing the particles which produce the 
63 To promote this increased action of the salivary glands, it is not ne- 
cessary that the substance should be placed in the mouth. The sight, or 
sometimes the thought, of any substance particularly gratifying to the 
taste, will have this effect, make the mouth water. The effect is a physical 
one, but the cause is a sympathy between the state of the mind and the 
action of the gland, of which we can only record the fact without giving 
any explanation. 
Section IT'.—156. Where is the sense of tasting situated? Describe the 
surface of the tongue, and the distribution of the nerve of taste. 
157. How is ihe sensation produced ? 
158. Iu what two ways is this sense rendered more acute ? THE SENSE OF TASTING. 
131 
impression in closer contact with the nerves upon which 
the impression is produced. 
159. Attempts have been made to classify the varieties 
of taste, though with but little success. They are, how- 
ever, more distinct than the varieties in the sense of smell; 
for they have, to some extent, received distinct names, such 
as sweet, acid, bitter, metallic, etc. 
160. The taste is a sense of importance to us in enabling 
us to discriminate between wholesome and hurtful food. 
It is a general rule that those substances which are agree- 
able to the taste the stomach will easily digest, and those 
which are not agreeable, if swallowed, the stomach will 
not act upon and is disposed to reject. A person with a 
disordered state of the system, or when recovering from a 
long illness, may desire the most hurtful kinds of food; 
the taste may also be perverted by the use of tobacco, al- 
coholic drinks, or food seasoned to excess; but these are 
exceptions which do not invalidate the rule nor diminish 
its practical value. 
161. The taste, though capable of being abused in this 
capacity quite as much as any other faculty, is yet one of 
the prominent sources of innocent physical enjoyment; 
and it is intended to be so, not simply for the enjoyment 
which it affords, but also as the natural motive to us to 
take food. The act of eating is not made compulsory upon 
us and removed from the control of the will lest we should 
forget it, as that of breathing is, but it is specially stimu- 
lated by the gratification of the sense of taste, which is 
necessarily connected with it. As we naturally seek to 
159. How are the varieties of taste indicated ? 
160. What is the principal use of the sense of taste ? What is the general 
rule by which the taste should govern us in the selection of food ? What arc ex- 
ceptions to ttiis rule ? 
161. How is this sense made subservient to the continuance of life ? How to 
the preservation of health THE SENSE OF FEELING. 
prolong this gratification, it encourages ns to take our 
food not too rapidly, to masticate it sufficiently, and to 
mingle it thoroughly with the saliva, all of which are es- 
sential to continuance of health. 
Section V.—The Sense of Feeling. 
162. This sense has its seat in the skin and exists on 
the wiiole surface of the body, but is more acute in the 
hands and at the ends of the fingers. 
163. The skin is composed of two principal layers. 
The outermost is the cuticle (1, 1, Fig. 85). It is this 
Fig. 85. 
1, 1 The cuticle. 2, 2 The colored layer. 4, 4 The network of nerves on the 
surface of 5, 5, the true skin. Filaments of nerves go from this network into 
the papilhe, 8, 8, 8. 6. 6, 6 Nerves which divide to form the network. 
Section T*.—162. Where is this sense situated ? 
1G3. Of how many layers is the skin composed ? Describe the cuticle. The 
layer in which the coloring matter is found. Upon what does its quantity de- 
pend ? THE SENSE OF FEELING. 
133 
layer which is raised by scalds or blisters. It is destitute 
of nerves or blood-vessels, and is regarded as merely a se- 
cretion from the true skin and hardened by exposure. At 
the under surface of the cuticle is a thin layer (3, 3), 
consisting, not of a network, as was formerly supposed, 
and from which supposition it was called the rete muco- 
sum, but of unorganized gelatinous matter. It is secreted, 
as the cuticle is, from the true skin, but has not become 
hardened. It is, in fact, cuticle in a state of formation. 
It contains the coloring matter which 
is so abundant in the African63 and 
some other races, and which is never 
wholly wanting in the healthy Euro- 
pean. Its color, always more or less 
dark, varies with the race, the tempera- 
ment, and the habits of the individual. 
Fig. 86. 
164. The hair and nails are of the 
same nature as the cuticle, being se- 
cretions simply, and containing no 
nerves or blood-vessels, and possessing 
no vitality. The hair is formed in a 
sac or follicle (Fig. 86) situated in the 
substance of the true skin, and passing 
through the cuticle by a narrow open- 
ing. In the bottom of this sac cells 
are continually forming; one portion 
of which, as they advance, become an 
imbricated covering of the hair. The 
other portion of the cells go to form 
the central portion, and among these 
are found colored oily particles which give color to the 
a The base of the follicle 
where the cells are sup- 
plied which form both 
the covering and the 
interior portion of the 
hair, b Cells to form 
the exterior part of the 
hair, c The same cells 
taking the form and ar- 
rangement of imbri- 
cated scales, d The 
interior portion of the 
hair, the cells becoming 
elongated and giving 
the fibrous structure to 
the hair as it ap- 
proaches e, and pro- 
trudes beyond the skin. 
63 In the Albino there are the features and all the peculiarities of the 
African, except a total absence of color. 
164. Describe the growth of the hair. 134 
THE SENSE OF FEELING. 
hair. The growth of the hair depends on the accumula- 
tion of new cells at the base, which thrust forward the 
shaft of hair already formed. 
165. The nails are developed in a very similar way. 
Each nail may be regarded as a hair increased in size and 
flattened, or as a succession of hairs placed side by side, 
and the several sacs in which they are formed coalescing 
into one of sufficient width to receive the root of the nail. 
166. The true skin (5, 5, Fig. 85) is a dense, elastic 
membrane, situated in contact with the muscular parts of 
the body, and defends them from injury. It is covered 
with a plexus of nerves (4, 4), and the terminations seem 
to be coiled up so as to form little mounds (8, 8), which 
are called papillae. On the ends of the fingers they are most 
abundant, and disposed in rows. They contain the nervous 
filaments from the posterior roots of the spinal nerves. 
167. Almost all of the physical properties and states of 
bodies, such as form, hardness, locomotion, vibration, tem- 
perature, etc., are capable of acting upon the nerves of 
this sense. The nerves convey these several impressions 
to the brain, where the sensation is produced. 
168. This sense, when specially trained (as it often is 
by those whose business it is to judge of the fineness of 
fabrics), becomes very acute. In. blind persons it almost 
answers the purpose of sight. By this sense they read 
rapidly with raised letters, and sometimes without the let- 
ters being raised. But it is of the highest importance to 
us without this special training. It is most favorably 
situated, at the extremities of the fingers, for extensive 
use. Scarcely any common employment, such as the use 
165. How are the nails developed ? 
166. Describe the true skin. 
167. How is the sense of feelina: produced ? 
168. Under what circumstances does this sense become specially trained? 
What is its use in an ordinary state ? THE SENSE OF FEELING. 
135 
of the needle or pen, could be carried on without it; but 
it is more indispensable in those processes which require 
special skill. 
169. It communicates certain kinds of knowledge which 
we could not receive in any other way. We could not, for 
instance, have the idea of temperature, of the existence of 
heat and cold, without this sense. It is also less likely to 
be deceived than most of the other senses, and hence it is 
employed to verify the evidences of the other senses.64 It is 
also made to co-operate with other senses : thus, we judge of 
distance by sight ordinarily, but not till we have learned 
by the sense of feeling at what distance certain differences 
take place in the appearance. We judge of form by the 
sight, but we also determine form by the sense of feeling, 
and then connect the ideas of the various forms with the 
impressions which they produce on the organs of sight. 
170. The systems of organs which we have hitherto con- 
sidered are subject to periodical suspension of their func- 
tions, constituting sleep. After giving attention to some 
of the processes of the repairing system, we shall be better 
prepared to understand the necessity for this suspension of 
activity. But the necessity exists, even if we can assign 
no reason for it. It is so far subject to the will that, if we 
choose, we can generally defer it several hours, but beyond 
a certain period it is impossible to resist the demand for 
it. The eyes close involuntarily; the voluntary muscles 
64 And Thomas said : “ Except I shall see in his hands the print of the 
nails, and put my finger into the print of the nails, and thrust my hand into his 
side, I will not believe. Then Jesus saith to him : Reach hither thy hand, 
and thrust it into my side, and be not faithless but believing.” 
169. How is it essential in the acquisition of certain kinds of knowledge? 
With what sense does it chiefly co-operate in making us acquainted with the 
external world ? 
170. What is sleep ? To what extant is it subject to our control ? 136 
THE SENSE OF FEELING. 
refuse obedience to the will; the external senses cease to 
act; all intellectual operations are suspended, and sleep 
inevitably supervenes. 
171. The amount of sleep needed varies with the tem- 
perament somewhat, with the age, the health, and the de- 
gree ot indulgence which a person will allow himself; but 
the amount absolutely required by an individual who has 
acquired his full strength depends simply upon the amount 
of activity, physical and mental, which is put forth. From 
five to eight hours may profitably be given to sleep. Eight 
hours is probably better than less. It is mistaken economy 
to attempt to reduce the amount of sleep below what the 
system craves. 
172. It is, however, possible so to train the powers that 
some of them may be either not at all suspended, or but 
very partially so. Thus, a person may accustom himself 
to sleep while riding on horseback, but there must be the 
continued exercise of sufficient muscular effort to keep 
the erect position. A physician will accustom himself to 
sound sleep in every other respect, while the sense of hear- 
ing is so far awake that his own name, though spoken in 
a low voice, will always arouse him. 
173. With most persons, however, sleep is for several 
hours complete; that is, all of the faculties which are sub- 
ject to it are comnletely suspended. But the continuance 
of this suspension is not the same for all of the faculties. 
Some, which have become sufficiently rested, begin to act 
before the others are aroused. Some persons plan their 
business for the day while the muscular powers and the 
senses are still asleep; the mind being first sufficiently 
rested for renewed activity. Under the same circum- 
171. How much sleep is necessary ? 
1 72. Do the faculties all sleep ? 
173. Do they all require the same amount of sleep ? Give examples of the 
activity of certain powers while the others are asleep. THE SENSE OF FEELING. 
137 
stances there is no doubt but that difficult problems in the 
arts and mathematics have been solved. It may be called 
dreaming, but it is simply an energetic action of the in- 
tellectual powers, rendered more perfect, because none of 
the powers of the system are otherwise employed, and be- 
cause the succession of thoughts is not interfered with by 
impressions coming from without. When the powers of 
voluntary motion are awake and the others are asleep, the 
person may take the most active exercise, or walk, some- 
times for miles, without arousing the other powers. 
174. Incubus, dr nightmare, admits of a similar expla- 
nation. When the mind first awakes, the train of asso- 
ciations may, from various causes, be of a disagreeable 
character. Particular ideas may have been so constantly 
in the mind before sleep came on that they most readily 
return. The imminent danger from which we had escaped 
the previous day may have impressed us so vividly, that 
the thoughts of it first occur to the mind when its powers 
are aroused. A sudden noise, an uncomfortable position, 
cold feet, or disturbed digestion, may predispose the mind 
to alarming conceptions. Every conception is, by our con- 
stitution, attended with a belief of the existence of the 
object to which the conception corresponds. In case of 
incubus, the object of conception does not exist, and yet, 
as the senses, which are the corrective agents, are asleep, 
there is necessarily a belief that it does exist. There is 
no avenue open by which a person’s mind can be reached 
to convince him that his conception is erroneous. He 
therefore suffers all that would result from real danger; 
at the same time the power of muscular action is asleep, 
and he can make no efforts to relieve his condition. 
175. Dreaming seems to consist in a certain degree of 
174. How is incubus explained ? 
175. I)reaming? 138 
GENERAL QUESTIONS. 
activity of the mind, while some of the other powers are 
also active to such an extent that they are continually in- 
terrupting the succession of thoughts, and yet do not con- 
trol them. Hence arises the want of continuity in our 
dreams and the succession of such incongruous ideas. 
Hence, also, the observation, so often made, that such sleep 
does us but little good; it does not rest us, and simply be- 
cause it is not sleep. 
GENERAL QUESTIONS ON THE NERVOUS SYSTEM. 
What are the parts contained in the nervous system ? 
Chapter I. Section I.—What is the subject of this section ? Describe the 
membranes of the brain and the duplications. What are the divisions of the 
brain ? Describe the surface of the cerebrum and the connection of the hemi- 
spheres. Of what substances is the brain composed, and how are they arranged 
in the several divisions ? What are the functions of the brain ? How are they 
to be learned ? Why not from an examination of the organization of the brain ? 
What is the first law in reference to the use of the brain ? WTiat are the results 
of a proper exercise of the brain ? Can the brain be overworked ? What are the 
practical rules in this respect ? Upon what does the healthy action of the brain 
depend ? How should a naturally excessive activity be managed ? How do the 
emotions affect the intellectual operations ? 
Section II.—Describe the spinal cord. What are the functions of the white 
substance of the brain ? Of the gray substance ? 
Section III.—What are the nerves ? Describe the cranial nerves. Describe 
the spinal nerves. Describe the origin of the spinal nerves. Their distribution. 
How is a general nervous sympathy established ? Describe the great s^mpa--j» 
thetic. What are the functions of the nerves ? Describe those of special sen- 
sibility. What arc the nerves of general sensibility ? What sensations are 
dependent upon these nerves ? How do they protect the body ? Is their sensi- 
tiveness ever injurious ? Give examples of the adaptation of these nerves to 
particular purposes. What are the nerves of voluntary motion ? , What is the re- 
lation between the nerves of motion and those of sensation? What are the 
nerves of involuntary motion, and what are the particular functions of each ? — 
Chapter II. Section I.—Describe the external parts of the eye. The internal 
parts. The action of the refracting substance upon the rays of light. How is 
vision produced ? What is the direction in which a visible object is seen ? Why 
are objects seen erect ? Why is but one object seen ? How is spherical aberra- 
tion prevented ? How does the eye adapt itself to different decrees of light, t 
To different distances ? How are long and short-sightedness corrected ? How GENERAL QUESTIONS. 
139 
does the eye adapt itself to different distances f What practical rules must be 
observed in the use of the eye ? 
Section II.—Describe the ear. The ear tube. The tympanum. The labyrinth. 
How is hearing produced ? By what substances must the vibrations be con- 
veyed ? Upon what does the perfection of the ear depend ? What parts are 
absolutely essential ? To what diseases is it subject, and how are they to be 
treated ? 
Section III.—Describe the organ of smelling. How is the sensation produced ? 
What evidences of design are observed in the position and structure of the nose ? 
What are the functions of the nose ? To what diseases is it subject ? 
Section IV.—Desoribe the organs of taste. How is the sensation produced ? 
What are the uses of this sense ? 
Section V.—Describe the organs of feeling. How is the sensation produced ? 
What are the purposes to which the sense of feeling is subservient ? 
What peculiarity have the mechanical and nervous systems to distinguish them 
from the repairing system ? How much sleep is required ? How are the different 
powers affected by sleep ? Explain the phenomena of sleep-walking, dreaming, 
incubus, etc. PAET IIL 
THE EEPAIKIHG SYSTEM. 
176. The body is subject to constant waste. The vital 
motions, the mechanical forces of the body, the develop- 
ment of heat, and even the processes of thought, are neces- 
sarily connected with wear, and therefore waste. While 
the body is growing the supply must be greater than the 
waste; but when the body has attained its growth, the 
supply is exactly equal to the waste. Our food, that is, all 
that is taken into the system, whether in the solid, liquid, 
or gaseous form, constitutes this supply. 
177. Our food, regarded in its more limited sense, con- 
sists of certain chemical combinations which depend for 
their existence wholly on the processes of vegetable life. 
We cannot produce them by the chemical processes of the 
laboratory. It is only by that secret working of the Di- 
vine power which we call vegetable growth, that they can 
be produced. The only invariable constituents are oxygen, 
hydrogen, and carbon. To these are frequently added 
nitrogen, and sometimes phosphorus, sulphur, and lime. 
The chemist can effect*various combinations of these sub- 
stances, but none which constitute food. Vegetable life 
176. From what arises the waste of the system ? What is the object of 
food ? How much is necessary ? 
177. Why is vegetable life necessary to animal life ? What are the invariable 
constituents of food ? What others are frequently contained in it ? What divi- 
sion is made of the materials for our nutriment ? THE REPAIRING SYSTEM. 
141 
is, then, a condition of animal life, and therefore of human 
life. 
But our food, though only the product of vegetable 
growth, has often been still further elaborated by animal 
life, so that it properly receives the name of animal food. 
One of the most common divisions of the materials for our 
nutriment is, therefore, into animal and vegetable food. 
178. We have seen that food may consist of oxygen, 
hydrogen, and carbon, without nitrogen. These three, in 
due proportion, constitute the sugars, the fats and oils, and 
all of the farinaceous varieties of food. They have been 
supposed to support the respiration of the system to great 
extent, but never to enter into the formation of the tissues 
of the body. They have, therefore, been called respira- 
tory elements, or non-nitrogenized elements. 
179. But much of our food contains nitrogen in combi- 
nation with the other three elements, and is employed in 
the formation of the flesh, the membranes, and other tis- 
sues of the body. It constitutes, therefore, the nutritive 
or nitrogenized portion of the food. The elements of nu- 
trition may take the form of fibre, as in the lean meat of 
animals; of gluten, as in the adhesive portion of wheat 
flour; of casiene, of which cheese principally consists; or 
of albumen, as in the white of the egg. This distribution 
of food into elements of respiration and elements of nutri- 
tion is important, in order to understand the vital changes 
in the system. 
180. The processes of receiving food, of whatever form, 
into the system, of elaborating it, and then of eliminating 
it, comprise all of the functions of the repairing system. 
178. What are the constituents of the respiratory elements ? What varieties 
of food belong to this class ? 
179. What are the constituents of nutritive food ? What four forms may this 
kind of food take ? 
180. Give an analysis of the repairing system. 142 
OF DIGESTION-. 
But a full examination presents to us, 1st, a digestive sys- 
tem, by which food is taken into the body and by which 
the nutritive part is separated from the useless and intro- 
duced into the blood ; 2d, a circulating system, an arrange- 
ment of tubes and forcing apparatus by which the nourish- 
ing fluid, the blood, is carried through the body and ap- 
propriated to the building up of the several parts; 3d, a 
respiratory system, an arrangement by which the oxygen 
of the air is incorporated with the blood, carried to all 
parts of the body, and is thus enabled to decompose (burn) 
the structures which the food has built up; 4th, an ab- 
sorbent system, a kind of scavenger arrangement by which 
such material as has for any purpose been removed from its 
regular channels may be picked up and again made use of; 
and 5th, a secreting system, by which all material, as it be- 
comes refuse, may be removed from the body. There are, 
therefore, five classes of organs belonging to the repairing 
system.55 
CHAPTER I.—OF DIGESTION, 
181. The food is not in a condition to be used in the re- 
pairs of the body without undergoing many changes, all 
designed to render the food soluble, so that in the liquid 
state it may be absorbed into the system and mingled with 
66 In this analysis of the repairing system it is the object to name only 
such functions as constitute one complete circle, and thus associate the sev- 
eral classes of these organs naturally together. It is not intended to be a 
full enumeration of these functions : the secretions for lubrication, the ab- 
sorption of chyle, the development of animal heat, and many others 
equally important, belong to this system. 
Chapter I.—181. What form must food take before it can be absorbed into 
the system ? What processes are necessary in completing the work of digestion f THE ORGANS OF MASTICATION AND DEGLUTITION. 
143 
the blood. Part of this process is mechanical, and is per- 
formed by mastication. Part of it is chemical, and is per- 
formed in the stomach and intestines. Part of it consists 
in separating the nutritious from the useless portions. 
Such is the general object of the digestive system. 
182. The abdomen, which is the cavity containing the 
principal digestive organs, lies between the thorax and 
pelvis, and is lined by a serous membrane called the peri- 
toneum. It secretes a fluid by which the interior of the 
abdomen is moistened and lubricated. It has another im- 
portant office, that of forming the outside coat of the stom- 
ach and most of the other viscera of the abdomen. 
Section I.—The Organs of Mastication and Deglutition. 
183. These organs are the teeth, salivary glands, the 
tongue, the pharynx, and the esophagus. 
184. The teeth are composed of 
ivory and enamel. The ivory (2, Fig. 
87) is harder than ordinary bone, and 
constitutes the principal part of the 
tooth. The enamel (1) is the densest 
material in the body. It is a thin layer 
on the outside of that part of the tooth 
not imbedded in the alveolar process. 
The purposes to which the teeth are 
subservient require that they should be 
composed of materials too compact to 
allow nerves and blood-vessels to pene- 
trate them ; hence the teeth, unlike the 
Fig. 87. 
Section of a MolarTooth. 
1 The enamel. 2 The 
body of the tooth, com- 
posed of ivory. 3 The 
cavity in the centre of 
the tooth, in which is 
seen the terminations 
of a nerve, 4, a vein, 5, 
and an artery, 6. 
182. Where are the organs of digestion situated? What is the name and 
office of the lining membrane of the abdomen ? 
Section I.—1 83. What are the organs of mastication and deglutition ? 
184. Describe the teeth. 144 
THE ORGANS OF MASTICATION AND DEGLUTITION. 
other osseous parts, when injured cannot be repaired by 
any natural process. Hence, also, they are developed in a 
different way from that of any other organs. 
185. The first indication of the formation of a tooth is 
the existence of a small transparent vesicle in the interior 
of the alveolar process. That portion of the vesicle corre- 
sponding with the body of the tooth gradually enlarges till 
it acquires the size the tooth is to have, and is filled with 
a transparent liquid. The outer surface of this vesicle 
soon deposits a shell of ivory, of the same shape and 
nearly of the same size which the crown of the tooth is to 
have after it emerges from the gums. After the shell is 
formed, the vesicle remaining within it continues to de- 
posit ivory, and thus becomes itself reduced in size as the 
walls of the tooth become thicker, until only a small hol- 
low (3) is left, which the perfect tooth always contains. 
This hollow is still lined by the vesicle, and receives an 
artery, a vein, and a branch from the fifth pair of cranial 
nerves. 
The tooth is covered with another membrane, which de- 
posits from its inner surface a layer of enamel (1) on the 
body of the tooth. 
The body of the .Doth being now completed, the central 
vesicle begins to be produced into one or more smaller 
prolongations, according to the number of roots which the 
tooth is to have. While the roots are forming, the body 
of the tooth is thrust forward and cuts through the 
gums. 
The first set of teeth contains but twenty, the double 
molars being wanting. As the alveolar processes of the 
child enlarge, these teeth become loose, the roots are ab- 
sorbed, and they are easily extracted. 
185. How is the ivory produced ? The enamel? The root? Describe the 
first set of teeth. ♦THE ORGANS OF MASTICATION AND DEGLUTITION. 
186. The second set consists of thirty-two, eight in 
each jaw on each side. The first and second in front (1, 
2, Fig. 88) are thin, have sharp, cutting edges, and are 
Fig. 88. 
The Second Set of Teeth in both jaws. 1, 2 The incisor teeth. 3 The canine 
teeth. 4, 5 The single molar teeth. 6, 7, 8 The double molar teeth. 
called incisor teeth. The third (3) is a strong tooth deeply 
set, is brought to a blunt point, and is called the canine 
tooth. The fourth and fifth (4, 5) have each one root, 
somewhat flattened surfaces, and are called single molar 
teeth. The sixth, seventh, and eighth (6, 7, 8) have three 
roots in the upper jaw and two in the lower, large bodies, 
broad surfaces, and are the double molar teeth. Thus there 
are eight incisors, four canine teeth, eight single molars, 
and twelve double molars. 
187. The teeth are designed to last a lifetime, and 
should, therefore, be carefully attended to. In the first 
place, care should be taken to prevent deformity. If the 
first teeth are not removed at the proper time, this does 
not prevent the teeth of the second set from coming, but 
186. The second set. 
187. What causes lend to produce irregularity in the arrangement of the 
teeth ? How may the irregularity in both cases be prevented ? 146 
THE ORGANS OF MASTICATION AND DEGLUTITION. 
it compels them to make their appearance where they 
ought not to be, either back of the other teeth, so as to be 
in the way of the tongue, or in front of the other teeth, 
so that the lips will scarcely cover them. If, however, the 
tooth of the first set is removed66 as soon as the second is 
perceived, the second will generally come into its proper 
place. 
It sometimes happens that the teeth are too wide for 
the space which they are to fill, and some of them must 
either be too prominent or they must be set irregularly. 
In such cases, the only way is to have a tooth removed, so 
that those which are left may have sufficient room. 
188. In the second place, no foreign substance should be 
allowed to remain on or between the teeth. They should 
be washed with a brush and water after every meal; other- 
wise particles of food which remain between the teeth will, 
by decomposition, render the breath offensive, and ulti- 
mately cause the decay of the enamel. 
A solid substance called tartar also frequently collects 
on the teeth, and extends toward the roots so as to loosen 
the gums and make them tender. When this has accu- 
mulated in considerable quantity, the aid of a dentist may 
be necessary to remove it; but its accumulation may 
always be prevented by proper attention to washing the 
teeth. 
68 The removal of teeth is, however, unnecessarily performed in many 
instances. It is the shortest way to overcome deformity, or to prevent 
toothache, or to remedy offensive breath ; but the peculiar character of the 
teeth should make us unwilling to resort to extraction except in extreme 
cases. Perhaps no fault is more common among dentists than to advise 
extraction for insufficient cause. The perfection of his art is to preserve 
the natural teeth—his last resort is to supply their place by artificial ones. 
188. Why should the teeth be cleansed after eating ? What is the effect of 
tartar upon the teeth ? THE ORGANS OF MASTICATION AND DEGLUTITION. 
147 
189. In the third place, great care should he taken to 
preserve the enamel. It is specially designed by its hard- 
ness to protect the ivory of the tooth ; but this property 
also increases its brittleness, and renders extremes of tem- 
perature, from taking very hot drinks or very cold, such as 
ice-water or ice, or any excessive pressure upon them, such 
as cracking nuts or cutting threads, likely to injure them 
permanently. When the enamel of a tooth is cracked, so 
that the air or the liquids of the mouth can get to the 
ivory, the tooth soon begins to decay, and is often reduced 
to a mere shell of enamel before we are aware of any im- 
perfection. 
But when the teeth do become defective, the decay can, 
if taken in season, be arrested by having the decayed por- 
tion removed and the cavity filled with gold. This is im- 
portant, in order to preserve the features, the voice, the 
health, and the means of masticating food. Its importance 
is indicated by the severe pain which, as a warning, is 
liable to attend Such decay. When, however, a tooth is so 
far gone that it cannot be preserved, it should be extracted 
at once. 
190. The saliva, by which the food as well as the in- 
terior of the mouth is moistened, is furnished by three 
pairs of glands. The parotid gland (1, Fig. 89) is situated 
below and in front of the ear.” The sub-maxillary gland 
(3) is on the inside, and near the angle of the lower max- 
illary bone. The sub-lingual gland (5) lies immediately 
under the tongue. The secretion from these glands is 
conveyed to the mouth by ducts (2, 4). 
67 It is this gland which is affected by a peculiar form of inflammation, 
called the “ mumps,” to which it can be subjected but once. 
189. How may the enamel be injured ? What is the result when the enamel 
is injured ? What course should be pursued when the teeth begin to decay? 
190. Describe the salivary glands. 148 
THE ORGANS OF MASTICATION AND DEGLUTITION. 
Fig. 89. 
The Salivary Glands. 1 The parotid gland. 2 The duct by which its secretion is 
conveyed into the mouth. 3 The sub-maxillary gland. 4 Its duct. 5 The sub- 
lingual gland. 
The secretion from the salivary glands depends in part 
upon the gratification of the taste ; hut it is also promoted 
by the motions of the jaw in mastication. This is one rea- 
son why food should be eaten sloAvly and well masticated. 
191. The tongue is attached at its base to the os 
hyoides, and the motions of this bone, by its proper mus- 
cles, carry the tongue backward or forward and raise or 
depress it. The tongue itself also consists of muscles, so 
that it can be shortened or elongated, and applied to all 
parts of the mouth. It is the principal organ of taste, 
and one of the most essential modifiers of sound; but, as 
connected with mastication, its office is to control the food 
in the mouth till it is swallowed. 
192. The pharynx is the back part of the mouth, 
and is at the same time the upper portion of the tube 
192. Describe the pharynx. What are the principal openings into the 
pharynx ? Of what are the sides of the pharynx composed ? 
191. The tongue. What are its functions ? 149 
THE ORGANS OF MASTICATION AND DEGLUTITION. 
which leads from the mouth to the stomach. From the 
upper posterior part, the Eustachian tubes lead to the 
tympanums of the ears; in the upper front side are the 
two openings leading to the nostrils, and at the base of the 
tongue on the front side is the opening into the larynx 
and trachea. The pharynx is surrounded by muscles so 
arranged that by their contraction it can be reduced in 
length, and its sides can be brought nearly together.58 
193. The esophagus (Fig. 90) is a continuation of the 
pharynx to the stomach. It is a fleshy tube composed of 
Fig. 90. 
The Esophagus, a b Circular muscular fibres, c A layer of longitudinal 
muscular fibres outside of the circular. 
two sets of muscular fibres, of which the inner ones {a, h) 
are circular, and serve to diminish its diameter, while the 
outer ones are longitudinal (c), and by contraction tend to 
shorten the tube. 
5S The mucous membrane, with which this and all other parts of the 
alimentary canal are lined, is very liable to inflammation, producing 
“ colds.” 
Just at the entrance of the pharynx there are two glandular bodies, the 
tonsils, which probably serve some important purpose in the system, but 
their use is not saiisfactorily known. They are very liable to inflammation 
and permanent enlargement; in this state they obstruct the breathing, es- 
pecially in sleep. They often almost or quite stop the breath, and they 
are liable to keep up an inflammation in the adjacent parts, which not 
unfrequently reaches the lungs. If, therefore, the enlargement cannot be 
reduced by medical treatment, it should be by surgical; they should be 
removed. 
193. Describe the esophagus. THE ORGANS OF MASTICATION AND DEGLUTITION. 
194. The object of these organs is to prepare the food 
for digestion and to convey it into the stomach. The 
lower jaw is provided with two pairs of strong muscles, 
to bring the upper and lower teeth firmly together, and 
with two other pairs of muscles, to give them a lateral 
motion and cause their rough surfaces to move over each 
other; and by this means the food, which is kept between 
the teeth, on the inside by the tongue and on the outside 
by the lips and cheeks, is reduced sufficiently to be received 
into the stomach—at the same time the saliva has been 
secreted and mingled with the food. In this state the 
portion of masticated food is taken up by the tongue and 
placed in the pharynx. The tongue is thus so bent back- 
ward that the epiglottis, which is a cartilaginous valve at- 
tached to the root of the tongue, is laid over the opening 
into the larynx,59 and the tongue itself, at the same time, 
closes the opening between the mouth and pharynx. By 
the same position of the tongue the membranous partition 
between the mouth and pharynx, called the velum palati, 
is raised up so as to close the orifices into the nostrils. 
The contraction of the pharynx itself closes the Eustachian 
tubes. At the instant when the food is placed in the 
69 The epiglottis is brought into the right direction to cover the opening 
into the windpipe, but the opening is not closed till the pharynx begins to 
contract. By this action the larynx is raised up and the orifice brought 
directly under the epiglottis. It is, therefore, closed as soon as pressure 
begins to be exerted upon the food in the pharynx, which would tend to 
press any of it into the windpipe. 
194. What is the object of these organs ? How is the food sufficiently reduced 
to be received into the stomach ? What are the muscles by which the vertical 
motions of the jaw are produced (see Appendix) ? Describe them. Describe the 
muscles by which the grinding motions are produced. What other preparaiion 
of the food is necessary besides mastication ? What Is the agency of the tongue 
in swallowing ? How are all the openings into the pharynx, except the esopha- 
gus, closed ? How is the food made to pass into the esophagus, aud how imo 
the stomach ? THE STOMACH. 
151 
pharynx and these principal orifices are closed, there is a 
strong involuntary contraction60 of the muscles composing 
the sides of the pharynx, and the masticated food is pressed 
into the esophagus, which, by the successive contraction 
of its circular fibres, forces it downward into the stomach. 
195. The food thus introduced into the stomach has 
been finely comminuted and mingled with saliva. The 
saliva is a slightly alkaline fluid, and contains a peculiar 
substance which has the property of converting the starch 
of food into sugar, thus commencing the process of diges- 
tion. This sugar readily passes into lactic acid, and may 
thus, in some cases, co-operate with the ordinary acid in 
the stomach in the work of digestion there. The amount 
of saliva secreted, about three and a half pounds a day, 
would indicate that it has an important office, but the 
changes above stated are all that are known to occur. 
Section II.—The Stomach. 
196. The alimentary canal, when it has passed 
downward through the diaphragm, becomes at once en- 
larged into a bag called the stomach (Fig. 91) of variable 
60 We see an obvious reason why the action of the pharynx should he 
involuntary and almost spasmodic. If it were otherwise there might be 
suspension of respiration ; for, during the act of deglutition, all commu- 
nication of the pharynx with the external air is cut off, and the epiglottis 
lies over the opening which leads to the lungs. Nature does not leave to 
our option any of the processes so essential to life. 
195. How much saliva is secreted per day? What action has it upon the 
food ? 
Section II.—196. Describe the form and position of the stomach. The coats 
of the stomach. THE STOMACH. 
Fig. 91. 
The Stomach, a The esophagus, b The smaller curvature, c The cardiac ex- 
tremity. (1 The pyloric extremity. / The larger curvature, g g The omeuuim. 
dimensions, but capable of containing, when moderately 
distended, from two to three pints. Its larger extremity is 
in direct contact with the diaphragm; and, as it lies ob- 
liquely across the spine from left to right, its smaller ex- 
tremity is considerably lower. The opening of the esopha- 
gus into the stomach is called the cardiac orifice, and that 
at the other extremity is the pyloric orifice. 
The stomach is composed of three coats. The exterior 
is of condensed cellular substance, and is in fact the peri- 
toneum attached to its muscular layers. This outer coat, 
being continuous with the lining membrane of the abdo- 
men, must retain the stomach in its place. The middle 
coat is muscular, and the fibres, though crossing each other 
in all directions, may, most of them, be classed as either 
longitudinal (L M, Fig. 93) or as circular (C M). The 
interior is a mucous layer, the inner surface of which is 
covered with papillae, which gives it a velvety appearance, THE STOMACH. 
153 
Muscular coat of the Stomach. 
and it is furnished with a large supply of nerves and blood- 
vessels. 
197. When food is taken into the stomach, the circula- 
tion in the mucous coat is increased, the color changes 
from a pale, or slightly pink, to a bright red, and a fluid, 
called the gastric juice, which is slightly viscid, transpa- 
rent, and feebly acid, is abundantly secreted. 
198. At the same time the muscular fibres of the stom- 
ach are successively contracted and relaxed, and the gastric 
juice is thus thoroughly mingled with the food, and con- 
verts it into a homogeneous, pulpy mass, called chyme. 
This process of changing the food to chyme is not a 
vital but a chemical one. If gastric juice be taken from 
the stomach and mingled with food in a state of minute 
division, and the ordinary temperature of the body be sus- 
tained, the formation of chyme will take place precisely as 
it does in the stomach.61 
61 Many of the statements made in reference to the gastric juice and the 
197. What is the effect upon the stomach of food received into it ? What are 
the properties of the gastric juice ? 
198. What change in the food takes place in the stomach ? How is it shown 
that the formation of chyme is not a vital process ? 154 
THE STOMACH. 
199. The food, as ordinarily taken, consists Oi the ele- 
ments of nutrition and of respiration in varying propor- 
tions, and both of these in combination with numberless 
forms of woody tissue. Tims, if the potato be grated to 
a pulp, the water with which it is washed will deposit a 
white granular substance. The clear water obtained after 
this deposition will, when the temperature is raised nearly 
to the boiling point, be filled with flaky shreds. The re- 
jected pulp is woody tissue, the granular deposit is starch, 
the flaky portion is albumen. The pulp is not food, the 
starch is respiratory food, the albumen is nutritive food. 
action of the stomach, were not regarded as fully proved, but only prob- 
able, until a circumstance occurred in Michigan, in the year 1822, which 
rendered it possible to subject them to the test of direct observation. 
Alexis St. Martin, a healthy young man in the U. S. service, was 
wounded in the side by the accidental discharge of a gun. The walls of 
the thorax and abdomen were lacerated, so that a portion of one lung was 
pressed out through the wound, and an opening was also made into the 
stomach. The patient was put under the care of Dr. Beaumont, a surgeon 
in the army. The wound in the thorax healed over. The edges of the 
Mound in the abdomen and of tha in the stomach adhered together and 
healed, leaving an opening into the stomach of turn and a half inches in 
diameter. At length a membrane was formed which shut down over it, 
like a valve, but did not adhere at the edges. This valve could at any 
time be pressed away, and the interior of the stomach and all its operations 
be exposed to view. 
Dr. Beaumont employed this young man after his recovery, and per- 
formed a series of elaborate experiments on the circumstances which would 
produce a secretion of the gastric juice, the state of the interior surface of 
the stomach at the time, the effect of alcohol, tobacco, and spices on the 
secretion of this fluid, also the effect of exercise, occupation of mind, ex- 
cited passion, etc. He apple d the stimulus of insoluble substances, put 
into the stomach to excite the secretion, and then removed it from the 
stomach to observe its action when applied to food in different conditions 
as to fineness, temperature, etc. He also instituted a full series of experi- 
ments upon the time required for the digestion of different kinds of food. 
199. Of what elements does food ordinarily consist ? Give instances of this THE STOMACH. 
155 
It may be shown that most substances that we eat have a 
similarly complex composition. The object of stomach 
digestion is to separate that which is food from that which 
is not, and then to render soluble and actually dissolve the 
nutritive elements. To do this is the function of the gas- 
tric juice. The daily amount of this secretion may be put 
down at fourteen pounds. The active principle of the 
gastric juice is a peculiar substance called pepsine, a 
nitrogen compound, not unlike the nutritive food. It 
seems to be part of the mucous coat of the stomach in 
the process of decomposition When slightly acidulated, 
as it is in the stomach, it tends to communicate the same 
change to similarly constituted bodies with which it comes 
in contact. Instances of this kind are of frequent occur- 
rence. Vegetable substances, apples for example, begin- 
ning to decay, will communicate to others that are sound 
the same change ; that is, they will bring on decay. The 
action of yeast is to put in operation in the gluten of flour 
the same chemical changes which the yeast itself is un- 
dergoing. In the same way the pepsine of the gastric 
juice,02 being a nitrogen compound in a state of change, 
will decompose the nitrogenized parts of the food in the 
82 It would seem that some vital process not yet explained is necessary 
to give to the gastric juice its solvent power. The composition of it has 
been carefully ascertained, and efforts have been made to produce it ar- 
tificially, but without success. If, however, a compound be formed resem- 
bling it in composition, and a small quantity of gastric juice be added (or 
a small piece of the stomach of a calf or ox), the whole will become capa- 
ble of reducing alimentary substances to chyme. 
complex character. What is the object of stomach digestion ? By what agent 
is this object effected ? What is the daily amount of gastric juice secreted ? 
What is the active principle in it ? In what condition is it ? Give other in- 
stances in which bodies in a state of decomposition communicate to other bodies 
the same action. How do the nutritive portions of the food pass out of the 
stomach ? Do they at once become a part of the blood ? How do the respiraiory 
portions pass from the stomach ? 156 
THE STOMACH. 
stomach so far as to separate them from the non-nitrogen- 
ized parts and from the woody tissue, and convert them 
not only into a soluble state, but also into that particular 
state of solution in which they are capable of passing freely 
through membrane. In this state they are absorbed by the 
interior surface of the stomach, and introduced into the 
blood. Thus one of the objects of digestion is accom- 
plished ; that is, the nutritive elements of the food have 
been furnished to the circulation. But the respiratory ele- 
ments pass on unchanged through the pyloric orifice into 
the duodenum. 
200. The digestive system requires more care than any 
other, partly because of its general importance, but espe- 
cially because our enjoyments depend so much upon it 
that we are in danger continually of overtasking it. The 
practical rules by which we should be governed in refer- 
ence to it are, however, very simple, and the reasons for 
them easily comprehended. They relate to the materials 
of food, the amount required, the frequency with which it 
should be taken, and the conditions of the system favor- 
able for its elaboration. 
201. The kinds of food. The system requires consid- 
erable diversity of food. The most suitable food soon loses 
its relish if we are confined to it. There must be diversity 
at each meal, and successive meals must not be a repetition 
of the same diversity. Even slight changes in the mode 
of cooking or flavoring will do much toward rendering 
food palatable, and therefore nutritious. 
202. We may not be able to assign reasons for the need 
200. Why does the digestive system require special care? To what four cir- 
cumstances do the rules refer by which the diet is to be regulated ? 
201. What is the first rule in regard to kinds of food ? 
202. Why do we teed both nutritive and respiratory food ? Are they both 
contained in every variety of food ? How Is the deficiency supplied ? In what 
proportions are the several kinds required f THE STOMACH. 
157 
of this general diversity, but there is obvious reason for 
the use of the nutritive and the respiratory kinds of food. 
Each has its special function, as will be shown in the 
chapter on respiration. Hence every variety of diet is made 
to contain both kinds. Nearly all of the articles of food 
contain both kinds, but if they do not, we instinctively 
supply the wanting kind. Thus, certain meats that are 
wanting in fat, are always eaten with gravy or other sub- 
stance rich in fat. Many kinds of fish are fried in butter 
for the same reason. The butter that we eat with bread 
and other vegetable foods, the pork cooked with beans, tbe 
oil and yolk of egg employed as dressing for salad, etc., 
are not accidental combinations of food, but such as expe- 
rience has taught us to be essential in furnishing the re- 
quisite materials for the wants of the system. It is be- 
lieved that when our food contains two-tenths of nutritive 
material, one-tenth of fat, and seven-tenths of sugar and 
starch, it will best meet the ordinary demand; but these 
proportions must vary with occupation, temperature, and 
the peculiarities of individuals. 
203. The additional inquiry may still be made, from 
what sources are we to obtain these nutritive and respira- 
tory elements of food ? We have seen that vegetable pro- 
cesses only can form those combinations of chemical ele- 
ments which constitute food. But these combinations we 
may obtain in the form in which the vegetable leaves them, 
or as they have been transformed into animal food, into 
the substance of the ouster, the salmon, or the ox. The 
kind of food designed by the Creator for any kind of ani- 
mal is best determined by examination of the peculiarities 
203. How are the kinds of food which are suitable for us indicated ? What 
peculiarity of organization is referred to ? What are its indications in regard to 
the food of man ? What other parts of our structure indicate a mixed diet ? Un- 
der what circumstances would a vegetable diet be appropriate? What class of 
persons require animal food ? 158 
THE STOMACH. 
of organization with which the animal has been furnished. 
One of these peculiarities of organization is the teeth, as 
indicating the kind of food required. The appropriate 
food of animals with canine teeth is flesh, while the ab- 
sence of them indicates that flesh would be inappropriate. 
Thus, the dog has only canine teeth and the horse only 
incisors and molars. In man the three kinds lire found, 
and it may be fairly inferred that both animal and vege- 
table food are appropriate. The apparatus of digestion, 
both in length and structure, is intermediate between the 
digestive apparatus of carnivorous and herbivorous ani- 
mals, and indicates, therefore, a mixed diet. 
It is probable that persons who put forth but little 
effort, either bodily or mental, may subsist on a vegetable 
diet, and enjoy perhaps better health than they would if 
they used animal food. But a person of whom much 
mental effort is required, or who is required to exert vig- 
orous and protracted muscular effort, must depend in part 
upon animal food. Such is the obvious conclusion on 
theoretical grounds, and such is the conclusion deduced 
from a wide generalization of facts in experience. The 
successful student must have animal food. The soldier, 
meeting hardship and exposure, must have animal food. 
The hard-working man in the field or the shop requires 
animal food. To reject such food is altogether at variance 
with the teachings of both our structure and our expe- 
rience. 
204. But a wide range of choice is left; when these con- 
ditions have been complied with. Our preferences and 
observation must then guide us. There is an endless di- 
versity of taste, and each individual may, as a general rule, 
allow his own taste to determine his selection of different 
20 I. Beyond the general considerations, how are we to he guided in Hie selec- 
tion of our food ? THE STOMACH. 
kinds of food ; nature, however, furnishes us checks upon 
this selection. Some kinds of food are found to stimulate 
the secretions too much, particularly in the warm season, 
and bring on summer complaints; other kinds of food 
seem to check the secretions, and are not digested at all, 
hut remain in the stomach till fermentation commences. 
Then either the gaseous eructations from the stomach, or 
portions of the food itself rising into the mouth, enable us 
to taste and recognize the kind of food which the stomach 
will not digest. Cheese, cabbage, fish, etc., are thus often 
pointed out to individuals as injurious. Each person may, 
then, follow his natural preferences in the selection of 
his food, subject, however, to such modifications as are 
suggested by his observation of the effects of particular 
articles of food. These principles, judiciously applied, will 
lead to very different rules for different persons, but still, 
for each one, such rules as it is safe for him to follow.63 
205. There is, however, a diseased condition of the 
stomach constituting dyspepsia, in which the taste is 
scarcely reliable at all as a guide. The gastric juice is 
either sparingly secreted, or it is impaired in quality. It 
is necessary then to furnish such food as will, as far as 
possible, excite the mucous coat of the stomach to action. 
The covering of the kernels of grain, or any other sub- 
stance which gives coarseness of texture, have this effect; 
63 Persons who complain of being injured by particular kinds of food, 
often admit the soundness of these rules by saying that when they ate 
such and such articles they knew that they should be injured by them. 
The difficulty is not that the indications of nature are so obscure, but that 
we are so averse to following them. 
205. When is the taste not reliable as a guide ? What is the first object to be 
secured in the food of dyspeptic persons ? What kinds of food answer this pur- 
) ose ? What, other property must the loud possess? What kinds of lood are 
to be rejected on this ground ? 160 
THE STOMACH. 
and hence bread made of unbolted flour is one of the 
most suitable forms of food for such persons. But it is 
also desirable that the food be easily digested; hence, rich 
pastries of all kinds are objectionable for such persons. 
Kew bread is also unsuitable, because, when eaten, it be- 
comes an adhesive mass which does not allow the gastric 
juice to mingle readily with it. Hence, also, everything 
that tends to preserve substances, that is, to prevent spon- 
taneous chemical changes, wrould also tend to prevent this 
particular chemical change, of which digestion consists. 
Hence, preserves, meat which has been salted, any sub- 
stances which have been pickled, are suitable only for per- 
sons whose digestive powers are unimpaired and vigorous. 
206. Perhaps, strictly speaking, there is no such thing 
as liquid food; still we often take food into the stomach 
in a liquid state. Milk, especially, is of this kind, but it 
separates before digestion into solid and liquid portions, 
and the solid portion, in which the nutriment consists, is 
subjected to the ordinary process of digestion. It is cer- 
tain that the liquid portion of gruels and soups is also, in 
a great measure, absorbed before the nutritious part is 
digested, though it is not improbable that some of the nu- 
tritious portion is absorbed directly into the circulation, 
without going through the digestive process. 
Liquid substances are, however, as much required in 
the system as solids, though we may not regard them as 
food. The blood requires a certain proportion of water to 
give it fluidity; and as it is every moment giving off 
water from the system by perspiration and by the breath, 
it is necessary that water be supplied in considerable quan- 
206. How is liquid food received into the system ? Why does the system re- 
quire liquids 1 How are they taken into the system ? What objections exist to 
the use of tea and coffee? What circumstances would indicate that they may be 
Used ? Why are alcoholic drinks injurious ? THE STOMACH. 
161 
tity. This is absorbed by the stomach, and received at 
once into the blood. It is taken either in the form of 
pure water or some modification of it, and generally in 
connection with our food. This practice of taking drink 
in connection with onr food has sometimes been objected 
to, but it seems to be natural, and in harmony with the 
wants of the system. 
Tea and coffee have often been objected to as affecting 
the system injuriously. They undoubtedly contain prop- 
erties which, when taken to excess, have such effects, 
and if headache and want of energy result, when the 
stimulus of them is withdrawn, their use should be aban- 
doned. They, however, contain, as their essential prop- 
erty, a compound of nitrogen, which is probably useful, 
and, with certain kinds of diet, may be essential to the 
health. When taken moderately, they doubtless encourage 
a healthy action of the stomach, and 'of the general system. 
Alcohol, as a chemical compound, has nothing analogous 
to it in the system, and, so far as we know, never contrib- 
utes anything toward the formation of any of the tissues 
of the body. It contains the elements of respiration, and 
it may tend to give fluidity to the blood, as water does; 
but it also possesses other properties which specially unfit 
the blood for its functions. Its principal effect in the sys- 
tem is as an excitant, and if it be admitted that the physi- 
cian may sometimes avail himself of this property advan- 
tageously, its general effects in the community are such, 
that it would seem proper to forego any inconsiderable 
advantage which might, in extreme cases, attend its use, 
and banish it altogether. 
207. There are several modifications which food under- 
goes in the process of cooking, which in some degree affect 
207. What changes does food undergo by cooking ? 162 
THE STOMACH. 
its character. It is not the chemical constitution but its 
physical character that is changed. Thus, in the cooking 
of vegetables the cohesion is diminished. When meat is 
boiled a part of the cellular membrane is dissolved, while 
the muscular fibre which lies within is unchanged. The 
baking of bread simply breaks the vesicles in which the 
farinaceous part is held. Thus, the mechanical obstacles 
to the digestive process, which exist in the substances 
used as food, are partially removed by the cooking process. 
208. In connection with the cooking of food there are, 
however, several additions, such as salt, vinegar, mustard, 
and various spices. Some of these, particularly salt, are 
demanded in small quantity by the system. Others, with- 
out being absolutely necessary, may, by rendering food 
palatable, so far favor the secretion of the gastric juice, 
and their presence, in contact with the mucous membrane 
of the stomach, may stimulate it to activity; so that a 
moderate use of them is probably not deleterious. There 
is, however, no doubt but that the degree in which they 
are used is excessive, and, by over-stimulating the stomach, 
tends to weaken its power. 
A degree of warmth to the food considerably above the 
ordinary temperature of surrounding objects, is also a 
healthy promoter of the digestive powers; but the inju- 
rious habit is often acquired of taking food, especially tea 
and coffee, so hot as to injure the organization of the 
tissues. 
209. The quantity of food. From what has been 
said of the objects for which food is taken, it follows that 
the amount needed will be variable, depending upon the 
208. What are the effects of the several substances added in the cooking pro- 
cess to flavor food ? How is the system affected by the temperature at which 
some articles of food are taken ? 
209. How is the proper quantity of food indicated ? 163 
effort put forth and the degree of exposure to which we 
are subjected. The demands of the appetite are the natu- 
ral indication of the quantity needed. There is a period, 
at every meal, when the appetite is satisfied, and yet more 
food can be eaten without inconvenience or aversion. 
This indication of the appetite that the wants of the .sys- 
tem are met, though not obtruding itself upon our notice, 
always exists, and may with attention be observed. After 
this period whatever is eaten is not because the system 
craves it, but because it gratifies the taste, and is likely to 
be injurious. 
THE STOMACH. 
210. There are instances of a morbid appetite which it 
would be unsafe to follow; but there are always in con- 
nection with it other indications of disease, which leave us 
in no doubt that it is unnatural. 
There are often complaints of want of appetite, but it 
is safe to follow this indication and abstain from food. A 
person seldom suffers from abstinence when there is no 
craving for food. Some of the best medicinal effects upon 
the system are produced by this abstinence. The want of 
appetite is the warning of nature not to lay upon the sys- 
tem at such times the task of digestion. 
211. Times of taking food. The teaching of nature 
is to eat when we are hungry, but the desire for food is 
only periodical. It is undoubtedly best that we have 
stated times for eating, and eat only at those times. These 
periods should be often enough to meet the demands for 
repair, which are continually made by the system. The 
general practice of taking three meals a day is, probably, 
not objectionable, though some have contended that only 
two would be preferable. 
210. Is the appetite always a guide ? What is the indication when there is a 
Van*, of appetite ? 
211. How often should food be taken ? What objection exists to taking food 
between our regular meals ? What to eating in the evening just before retiring ? 164 
THE STOMACH. 
Lunches e veen meals cannot but be injurious. The 
stomach, like the organs of the body generally, requires 
periods of rest; when food is taken between meals, de- 
mands upon the stomach are made continually. For the 
same reason, the eating of fruit or confectionery, except 
at regular meals, is hurtful. The same objection lies 
against the habit of eating a short time before retiring. 
All of the involuntary powers are less energetic during 
sleep than when we are awake; digestion will therefore be 
feeble, the food will lie too long in the stomach, relish for 
the next meal will be diminished, and the power of the 
system to act upon it reduced. Besides these effects, 
dreaming is often induced, and thus sleep fails to refresh 
any of the powers of the system. 
212. Conditions upon which digestion depends. 
As the gastric juice is the principal agent in effecting the 
necessary changes upon the food, the circumstances most 
favorable to digestion are those most favorable to the 
supply of this secretion. If the system is in a healthy 
state, whenever the stomach is suitably distended with 
food, and sufficient blood is supplied to it, the secretion 
will take place. Digestion will depend then, in the first 
place, upon an active circulation of the blood. This re- 
quires that there should be considerable exercise, but not 
of a character to exhaust or depress the powers of the sys- 
tem, and that there should be an abundant supply of pure 
air for respiration. 
213. It is necessary, in the second place, that the blood 
be not deflected to other organs, but allowed to go to the 
stomach. This last condition is one very likely to be in- 
212. Upon what does digestion depend? Upon what does the secretion ot 
the gastric juice depend ? What are the conditions upon which an active circu- 
lation depends ? 
213. When there is active circulation, how may it be prevented from going in 
snfti lent quantity to the stomach ? DUODENUM AND ORGANS CONNECTED WITH IT. 
165 
terfered with. Time should be allowed not only for eat- 
ing but for digestion. The energy so characteristic of this 
country, drives the laborer from his meal at once to his 
work, the merchant to his counting-room, and the profes- 
sional man to his office. There is no interval of rest during 
which the stomach can command the whole energy of the 
system in digestion; and hence it is not surprising that 
that function is so often impaired. 
214. The mind may also be occupied involuntarily in 
such a way as to control the circulation and greatly inter- 
fere with digestion. Grief, melancholy, intense anxiety, 
all have this effect. Hence it is that travelling, visiting 
watering-places and the like, are often so serviceable. 
They divert the attention, and hence allow the circulation 
to resume its natural course, and to be employed in diges- 
tion whenever it is thus needed. 
The conditions of the system most favorable to digestion 
are those in which there is neither physical exhaustion, 
ennui, nor mental depression, but such physical activity 
as to keep up a free circulation of the blood, buoyant 
spirits, and moderate mental activity, as in ordinary con- 
versation. 
Section III.—The Duodenum and Organs connected with it. 
215. The duodenum (p, e, i, Fig. 93) (also 5, Fig. 94) 
is the commencement of the small intestine, from which it 
is distinguished by being more closely confined in its po- 
sition, and by its not being connected with the spine by 
the mesentery. It arises from the stomach at the pyloric 
214. What is the effect of close application of mind upon the digestive pro- 
cess ? What then are the conditions favorable to digestion ? 
Section 111,-2,15. Describe the duodenum. 166 
duodenum and organs connected with it, 
Fig. 93. 
e e The Duodenum, p The pyloric orifice of the stomach, g The bile sac, 
c The duct from the liver, o The pancreas. 
orifice, and is from eight to fen inches in length. Like 
the stomach and the intestines, it is composed of three 
coats. 
216. The liver (3, Fig. 94) is the largest gland of the 
body, and is situated on the right side of the abdomen, 
in contact with the diaphragm above, and Avith the pyloric 
portion of the stomach below. It receives a small artery 
by which its nourishment is conveyed to it. But it is 
supplied with a large amount of venous blood. It is the 
only gland which is supplied with venous blood, and a 
special arrangement of blood-vessels called the portal sys- 
tem is furnished which collects the venous blood from all 
of the other digestive organs and empties it into this 
gland. The bile is secreted from this blood, and is a 
slightly viscid fluid, greenish, bitter, and alkaline. There 
is a duct (c, Fig, 93) leading from the liver to the duode- 
num, and another from the bile sac (g) opening into it. 
216. The liver. How is it supplied with blood ? For what is the venous 
blood furnished ? What are the properties of the bile ? How is it disposed of 
during digestion and during the intervals ? DUODENUM AND ORGANS CONNECTED WITH IT. 
167 
Fig. 94. 
The Digestive Organs. 1 The esophagus. 2 The stomach. 3 The liver. 4 The 
hile sac, its duct opening into the hepatic duct. 5 The duodenum, 8 The pan- 
creas. 7 The email intestine. 8 to 13 The large intestine. 13 The spleen. 
During digestion, the bile passes as it is secreted directly 
to the duodenum ; but during the intervals of digestion, 
after filling the duct, it passes backward into the bile sac, 
and is retained until digestion again commences. 
217. The average daily secretion of bile is about three 
and a half pounds. It consists mainly of two ingredients 
—the coloring matter, which is a merely refuse substance 
not again used in the system, and some oily materials, 
217. What is the amount of daily secretion of hile ? What are ita two chief 
ingredients ? How is the saponaceous portion disposed of 1 168 
DUODENUM AND ORGANS CONNECTED WITH IT. 
combined with soda, forming a peculiar variety of soap. 
This is reabsorbed as part of the chyle. Tims a portion 
of the bile becomes excrement, and to this end the liver is 
an organ for eliminating waste material from the body. 
The saponaceous portion goes again into the circulation, 
either as an economical use of material, or it may serve 
some useful purpose not fully understood in connection 
with the absorption of chyle. 
218. The secretion of bile is from the portal blood, re- 
garded simply as venous blood, but it also contains the 
nutritive elements of the food which have been absorbed 
by the stomach. The liver performs important changes 
upon this newly admitted portion of the portal blood. 
The general object seems to be to prepare it for being acted 
upon by the respired oxygen. Accordingly, it converts a 
portion of the new material into liver-sugar, a form of 
combustible food in the best condition for use in the 
lungs.94 The blood-cells in a state of formation seem also 
64 An intimate relation exists between the liver and the lungs In a 
cold climate we respire more oxygen than when the temperature is milder. 
The liver seems then to prepare all of the elements of respiration which 
the food furnishes for use in the lungs. Even then there may be not 
enough, and the oxygen acts upon the lungs themselves, inducing con- 
sumption. In warm climates, on the contrary, because of the diminished 
supply of oxygen, the respiratory food is not all used. The liver returns 
it to the intestines. It comes back to the liver, and is again returned. The 
liver becomes thus overtaxed and diseased. Hence the prevalence of pul- 
monary diseases in cold climates and of bilious diseases in warm climates. 
The liver is larger in proportion as the lungs are smaller. In cold- 
blooded animals the respiration is very feeble and the liver very large. 
Such animals take a large amount of food at once, and are then subject to 
long fasts. The food is digested and furnished to the circulation. Pass- 
ing many times through the liver, a portion is each time fitted by it for 
use in respiration. It is thus retained in the system until, by slow respi- 
ration, it is all consumed. 
218. Has the liver other functions besides secreting bile? What is the first 
change upon the new material in the liver f What other function of the liver ? DUODENUM AND ORGANS CONNECTED WITH IT. 
169 
to receive important additions in their passage through 
the liver. 
219. The pancreas (o, Fig. 93) is a gland about six 
inches in length, situated behind the stomach and across 
the spine. It secretes a fluid resembling the saliva, which 
is conveyed by the pancreatic duct into the bile duct, 
and is thence emptied into the duodenum. 
220. The amount of pancreatic fluid is two or three 
times as much as the bile, and has no other known agency 
except the change which it effects in the digestive process. 
The chyme as it enters the duodenum contains all of the 
oily, saccharine, and starchy ingredients of the food nearly 
unchanged. The action of the stomach has been to sep- 
arate the nitrogenized compounds and introduce them 
into the portal blood. The pancreatic juice, influenced to 
great extent by its alkaline character, changes starch into 
sugar. Sugar, whether taken into the system as such or 
derived from the changes upon starch, is decomposed into 
lactic acid, and in this condition is readily absorbed. 
221. The pancreatic juice, while it does not decompose 
the oily constituents of food, does bring them into the 
condition of an emulsion. This will be best understood 
by remembering tnat milk is essentially an emulsion. 
The water, which is its chief constituent, does not dis- 
solve the butter, but it holds it suspended in particles of 
extreme minuteness, and it is only by long standing that 
the oily particles rise to the surface. The white color re- 
sults from these suspended particles of oil. The pancreatic 
juice is capable of bringing into minute division the oily 
219. Describe the pancreas and its secretion. 
220. What is the daily secretion from the pancreas ? What are the constitu- 
ents of the chyme ! What is the action of the pancreatic secretion on starch ? 
Upon sugar ? 
221. Upon the oleaginous portions of food ? Give the illustration. 170 
THE INTESTINES. 
substances of the food, and holding them in this condition 
of an emulsion. 
222. It is then the office of the pancreatic juice to bring 
into a condition suitable for absorption all of the respira- 
tory elements of the food. The respiratory portion of the 
food, in this condition, is called chyle. It has a milk-like 
appearance, and consists of the useful portion of the bile, 
of an emulsion of the oily parts of the food, and of the 
starchy and saccharine parts, mostly in the form of lactic 
acid. There remains then only that part of the food 
which is incapable of being vitalized and appropriated. 
The two substances in this condition enter the small in- 
testine. 
Section IV.—The Intestines. 
223. The small intestine (7, 7, Fig. 94) is a continu- 
ation of the duodenum, and is about five times the length 
of the body. 
224. This intestine is supported by the 
peritoneum, which is the membrane that 
lines the cavity of the abdomen. When 
this membrane (a, Fig. 95) comes to the 
spine, s, it goes forward so as to inclose 
the intestine e, then returns to the spine 
and continues its course in the direction 
b. This duplicature of the peritoneum 
forms the outer coat of the intestine, and 
the double membrane between the intestine and the spine 
Horizontal Section of 
the Abdomen, a b 
The peritoneum, s 
The spine, e The 
small intestine, i c 
The mesentery. 
222. What, then, is the function of the pancreatic juice ? What is the product 
called ? Of what does it consist ? 
Section IF',—223. Describe the small intestine. 
224. Describe the mesentery and lacteals. 'the intestines. 
171 
is called the mesentery, A portion of the mesentery 
(3, 3, Fig. 96) is represented as supporting the intestine; 
and lacteal vessels (1, 1) come forward to the intestine, 
and probably open into it by capillary orifices. 
225. The intestines are subject to a constant vermicular 
motion, by which their contents are made to move slowly 
through them. The particles of chyle, as they pass along 
the intestine, are gradually absorbed. The veins undoubt- 
edly absorb, to considerable extent, those which are not 
oleaginous. These veins are feeders to the portal system. 
Thus all the products of stomach digestion and part of 
the products of intestinal digestion are subjected to the 
action of the liver before they pass to the heart and lungs. 
The lacteals absorb the remaining portions of the chyle. 
226. The lacteals pass through small glands within the 
mesentery, and continue to unite as they approach the 
spine, where they form but one vessel (4), the recep- 
tacle of the chyle. This vessel forms a continuous 
tube up the spine, where it is called the thoracic duct, 
and opens into the vein (the descending vena cava, at 10) 
which collects the blood from the head and upper ex- 
tremities. 
227. The chyle, as it appears in the lacteals, contains 
also some nutritive elements, whether derived from the 
chyle in the intestine or absorbed from the contiguous 
blood-vessels. In fact, the oil globules seem to be coated 
with a substance of this kind. Some of these oil globules, 
in passing through the mesenteric glands, become incipient 
blood-ceils, though they have not yet assumed the red 
color. It seems also that these glands convert some of 
225. How are the contents of the intestines kept in motion? How is the 
chyle disposed of? Describe the actions of the veins. 
220. What is the function of the lacteals ? 
227. How is the chyle in the thoracic duct different from that which is found 
in the lacteals at their origin ? How is the change made ? 172 
THE INTESTINES. 
the nitrogenized material which passes through them into 
fibrine. So that the chyle, as it appears in the thoracic 
duct, contains both fibrine and incipient blood-cells. 
228. We have seen that part of the new material from 
the food, as it passes through the liver, is converted into 
liver-sugar, and the new blood-cells undergo modification. 
The other part of the new material is changed in passing 
through the mesenteric glands, some into fibre, the source 
of muscular repair, some into blood-cells, and a portion 
remains in its oleaginous state. Thus all of the useful 
portion of the food, after digestion, passes through glands 
which impress important changes upon it,65 making of the 
nitrogenized portions blood-cells and fibrine, and of the 
non-nitrogenized portions the substances best fitted to 
evolve animal heat. Thus we see where the greatest 
amounts of the material required in the system are elabo- 
rated. Exactly where the brain material and some other 
parts are formed has not yet been determined. 
229. Thus we have traced the changes upon the food 
till it enters the veins. It is now a constituent of the 
65 It seems somewhat strange that the changes of the new portions of 
the blood in the liver are the formation of liver-sugar, a non-nitrogenized 
compound, though the nitrogenized food which had been digested by the 
stomach passes into the portal blood; and that the principal changes ef- 
fected in the mesenteric glands are the formation of blood-cells and of 
fibrine, both nitrogenized compounds, though the materials seem to have 
been derived wholly from the digestion of non-nitrogenized food. 
It may be said, in explanation, that only a very small part of the mate- 
rials newly received into the blood need any change, and that in the great 
amount of absorption and secretion in the digestive tube there is not 
likely to be such a complete separation of the two kinds of food as a gen- 
eral description of the process would seem to indicate. 
228. Is digestion the only modification which the food undergoes before it 
enters the blood ? Is it known where all of the materials for repair are elaborated ? 
229. Is the useful portion of the food all transferred to the veins f Where 
must we look tor any further changes upon it ? THE INTESTINES. 
173 
Fig. 96. 
1, 1 Lacteals. 2, 2 Part of the mesentery containing mesenteric glands. 3, 3 
Part of the small intestine. 4 The receptacnlum chyli, continued upward as 
the thoracic duct, which opens into the descending vena cava at 10. 5, 5. 5 
Lymphatic vessels opening into the receptaculnm chyli. 6, 6 The diaphragm. 
7 The aorta. 8 The spine. 9 The descending vena cava. 
blood, and its further course must, therefore, belong to the 
circulating system. 
230. The large intestine (8 to 12 inclusive, Fig. 94) 174 
OF THE CIRCULATION. 
is about one-fifth the length of the small intestine, hut it 
has much greater capacity. The nutritious portion of the 
contents of the small intestine having been absorbed, the 
excrementitious portion is received by the large intestine, 
and, after being conveyed by a circuitous course, is expelled 
from the system.66 
CHAPTER II—OF THE CIRCULATION. 
231. The circulating fluid is the blood. It contains 
the materials which are necessary for the formation of all 
the tissues of the body, such as brain, muscle, bone, etc., 
and those which are employed in the various repairs which 
the body requires; and we have seen how these materials 
are continually elaborated and furnished by the digestive 
process. 
232. The amount of blood has been variously estimated, 
but twenty pounds is probably about its average weight. 
233. If a portion of blood be taken from a vein and 
06 The excrement is lodged in the large intestine to prevent the neces- 
sity of constant depletion; but scarcely anything is more important to 
health than that the feces be evacuated daily, and it is better that it should 
be at a particular hour. Persons whose habits are not active, and whose 
respiration is feeble, communicate but little mechanical motion to the ab- 
domen, and the feces become hardened and may remain for days. This, 
however, cannot be without injury; the system should be required to 
conform to rule, and a constipated state of the intestines will then seldom 
occur. 
230. Describe the large intestine. 
Chapter II.—231. What is the circulating fluid? What are its peculiari- 
ties which fit it for serving the purpose of nutrition ? How does it receive the 
nutritious substance ? 
232. What is the amount of blood in the system ? 
233. What are the parts of which blood is composed ? OP THE CIRCULATION". 
175 
allowed to stand for a short time, a part of it becomes 
watery and nearly colorless. This is the serum, upon 
which the liquidity of the blood depends. The clot or 
solid portion can be reduced by repeated washings to a 
stringy and nearly colorless mass, which is fibrin. This 
is the nutritious part. That which has been washed out 
consists of blood-cells, upon which the color of blood de- 
pends, and which is essential to the proper effect of respi- 
ration upon it. 
Fig. 97. 
1 The pericnHiiim. 2 The heart. 3, 3 Blood-vessels from the heart. 4 The 
ir h-I. 5 The lungs. 6 The liver. 7 The stomach. 8 The large intestine, 
y, 10 The small imes.iiie. 176 
OF THE CIRCULATION. 
234. "We may regard the organs of circulation as a sim- 
ple hydraulic apparatus, designed to establish the motion 
of a liquid in a given direction, and through a given cir- 
cuit. It must then contain a set of tubes in which the 
liquid is to be conveyed, so fitted with valves as to prevent 
the motion in one direction and allow it freely in the other, 
and means of exerting the force necessary to produce the 
required motions of the fluid. The heart, arteries, and 
veins are designed to fulfill these conditions. 
235. The heart (see lith. pi. IV., Fig. 1) is inclosed in 
a strong cellular substance (1, Fig. 97), called the pericar- 
dium, the inner surface of which supplies the lubricating 
fluid for the motions of the heart. The mediastinum is 
the double membrane which comes forward from the spinal 
column to the sternum, and divides the thorax into two 
cavities. The heart, with its pericardium, is situated be- 
tween the two layers of the mediastinum (H, Fig. 98), en- 
Fig. 98. 
Fig. 99 
A Horizontal Section of the Tho- 
rax. The two membranes, 1,1, 
constitute the mediastinum. 2, 
2 The same membrane extends 
so as to line the cavity of the 
thorax, where it is the pleura 
costalis. 3, 3 The continuation 
of it. so as to cover the lungs, 
the pleura pulmonalis. 
1 The right auricle. 2 The right ventricle. 
8 The left auricle. 4 The left ventricle. 
5 The orifice from the right auricle to 
right ventricle. 6 The orifice from the 
left auricle to the left ventricle. 7 The 
pulmonary artery. 8 The aorta. 
234. Mrhat organs are necessary to constitute an apparatus for the circulation 
of the blood ? 
235. Describe the mediastinum. The pericardium. The position of the heart. OF THE CIKCULATION". 
177 
croacliing more upon the cavity of the left side than the 
right, with its apex directed downward and resting on the 
diaphragm. (See lith. pi. III.) 
236. The substance of the heart consists of a mass of 
muscular fibres, so arranged as to inclose four cavities. 
The first (1, Fig. 99) is the right auricle, and the second 
(2) is the right ventricle. The third cavity (3) is the left 
auricle, and the fourth (4) is the left ventricle. The 
auricles may be regarded as mere enlargements of the veins 
which bring the blood to the heart. The thick, strong 
muscular walls of the ventricles (2, Fig. 100) indicate that 
they are designed to give the principal force to the arterial 
circulation. Both ventricles contract at the same time. 
237. The orifice (1, Fig. 100) from the auricle (3) to the 
Pig. 100. 
Valves of the Heart and Arteries. 1 The oritice between the auricle and ven- 
tricle. 2 The muscular walls of the ventricle. 3 The auricle. 4 The ventricle. 
5, 5, 5 The fleshy and tendonous ligaments by which the valves of the heart 
are strengthened. 6 Valves of the arteries. 7 The descending vena cava. 8 
The ascending vena cava. 
236. Give the structure of the heart. 
237. Describe the valves of the heart. 
8* 178 
OF THE CIRCULATION. 
ventricle (4) is furnished with membranous valves, which 
easily yield when the blood passes in the direction indi- 
cated by the arrow (at 1); but when the ventricle (4) 
contracts, they are prevented from yielding by fleshy and 
tendonous strings (5, 5) extending from them to the walls 
of the ventricle.67 They, therefore, allow the blood to 
flow into the ventricle, but prevent its reflux. Those in 
the first ventricle are called the tricuspid valves; those 
in the second are the mitral valves. 
238. The arteries are the strong cylindrical tubes 
which convey the blood from the ventricles. They are 
composed of an exterior coat of condensed cellular sub- 
stance, upon which the strength of the artery principally 
depends, a middle coat of elastic membrane, with muscu- 
lar fibres interspersed, upon which the contraction of the 
arteTy depends, and a third membrane, with a smooth in- 
terior surface, the object of which is to diminish the fric- 
tion arising from the motion of the blood. 
239. The arteries, as they arise from the heart, are each 
furnished with valves (6, Fig. 100), which are so con- 
structed as to allow the blood to enter the arteries freely, 
but to prevent its going back into the ventricles. They 
are named the semilunar valves, and are the only ones 
which the arteries contain. 
240. The pulmonary artery (13, pi. Ill) arises from 
the right ventricle, and is distributed to the lungs. 
67 These strings, as stay ropes, not only support the valves, but they 
cause the blood and the chyle, which have just been emptied into it, by 
their rapid motion through the meshes thus formed, to be more thoroughly 
mingled together before going to the lungs. 
238. The arteries. 
239. The valves of the arteries. 
240. The pulmonary artery. OF THE CIRCULATION. 
241. The artery which arises from the left ventricle and 
is distributed to the body, is called the aorta (a b, pi. 
VI.) The first branches from the aorta are the coronary 
arteries, a small pair, which is distributed to the substance 
of the heart. The two carotid arteries (2) arise from 
the highest part of the arch of the aorta, and ascend 
along the neck to the base of the cranium, where they 
each divide into two portions, one of which supplies the 
brain and the other the face and the integuments of the 
head. The two subclavian arteries (3) also have their 
origin from the arch of the aorta, and supply the upper 
extremities. In its passage to the diaphragm, the aorta 
gives off small branches to the lungs and parietes of the 
thorax. Within the abdomen it gives off the phrenic 
artery (4), which is sent to the diaphragm, the coeliac ar- 
tery (5), which supplies the liver and pancreas, the stom- 
ach and the spleen, the mesenteric artery (6), which 
goes to the intestines, and the emulgent artery (7), which 
goes to the kidneys. As the aorta enters the pelvis, it 
divides into the iliac arteries (8), which, after sending 
branches to supply the external and internal parts of the 
pelvis, are distributed through the inferior extremities. 
242. The veins are the tubes by which the blood is 
returned from the different parts of the system to the 
right auricle of the heart. Like the arteries, they have 
three coats, but they are thinner and have less strength, 
though much greater capacity. They are furnished with 
a great number of valves (Fig. 101) in the different parts 
of their course. The veins have the same general distri- 
bution as the arteries (lith. pi. YIL). Those from the 
head, thorax, and upper extremities unite to form the 
descending vena cava (10, pi. III.). Those from the 
241. Describe the aorta and its branches. 
243. Describe the veins. 180 
OF THE CIRCULATION. 
Fig. 101. 
1 A vein. In the lower part the vein laid open to show the numerous folds, 2, 2, 
of the inner coat of the vein which act as valves. 3 The opening of a branch 
into a larger vein. 
abdomen and lower extremities unite to form the as- 
cending vena cava (9). These two veins meet at the 
right auricle. 
243. We may now trace the blood in its course 
through this system of vessels (lith. pi. Y.). It will be- 
come more simple if we regard the first auricle and ven- 
tricle as constituting one heart, and the second auricle 
and ventricle as constituting a second heart. Such divi- 
sion actually exists in some animals. Let us commence 
with the blood, as it is collecting from every part of the 
system {b, b, b) into the veins. We find these veins all 
lead to and terminate in the first auricle (1), from which 
the first ventricle (2) receives it, and by contraction sends 
243. The course of the circulation. OF THE CIRCULATION-. 
181 
it through the pulmonary artery into the lungs. The 
circulating fluid thus far has been dark blood. In the 
lungs it undergoes certain changes, and receives a florid 
color. It is then collected by the veins of the lungs and 
brought to the second auricle (3), from which the second 
ventricle (4) receives it, and by contraction sends it into 
the aorta to be distributed to all parts of the body, to be 
again collected by the veins. If we now regard these two 
hearts as brought together, and, to economize room, united 
into one organ, we shall have a correct idea of the human 
heart and of the circulation through the system. 
244. There are several distinct forces by which the 
circulation is promoted. The various movements of the 
body must be incessantly compressing the veins; and, as 
the valves prevent a reflux of the blood, these motions 
must contribute to carry the venous blood toward the 
heart. The suction power of the right auricle, and per- 
haps a slight contraction of the veins, have been supposed 
to assist the venous circulation. But the enlargement of 
the thorax at each inspiration, as it causes the breath, so 
it causes the blood to enter the thoracic cavity. More- 
over, the capillaries, by capillary attraction, draw the blood 
into them. Here the blood is changed, and then the capil- 
laries have but little attraction for it. It is, therefore, 
allowed to pass on. This attraction is the principal force. 
The arterial circulation is chiefly dependent upon the 
contraction of the heart. It is for this purpose that so 
large an amount of muscular power has been given to it. 
The arteries are also elastic and probably muscular. At 
each pulsation of the heart, the new blood which they re- 
ceive stimulates them to contract, and thus each wave set 
in motion by the ventricle is closely followed by a con- 
244. What are the forces by which the venous circulation is sustained ? How 
is the arterial circulation sustained f 182 
OF THE CIRCULATION". 
traction of the artery, and the motion of the blood is per- 
petuated to the capillary vessels, and perhaps beyond them 
into the veins. 
245. Without accurate calculation, we have very little 
idea of the quantity of blood thus sent through the sys- 
tem daily. The ventricle receives nearly two ounces of 
blood at each pulsation, which it discharges into the 
aorta about seventy-five times a minute, making nine 
pounds, or more than a gallon every minute, or two bar- 
rels an hour. 
246. Whenever the artery lies near the surface, the wave 
produced by each contraction of the heart can be distinctly 
felt, constituting the pulse. Its frequency varies with 
the mental states,68 the amount of exercise, the age, the 
sex, and the health. In young children, the beats are 
more than a hundred in a minute. The ordinary pulse 
of a healthy person in mature life is about seventy-five. 
In old age it may sink to fifty or less. But its most re- 
markable changes are those dependent upon the condition 
of the system. It is to the physician his most reliable in- 
dication of the degree and kind of diseased action.69 
68 Hence those poetic expressions, “ the heart leaps for joy,” “ melts 
with grief,” “ sinks within one,” and “ the blood curdles in the veins,” 
are not altogether figurative. 
69 It is one of the remarkable instances of adaptation in the system, 
that the heart is so sensitive to the slightest changes in the state of the 
blood, that its mode of contracting, and its frequency, indicate the exist- 
ence of disease in its very first stages, and yet the heart is not sensible in 
any degree to external contact. “ Hervey had an extraordinary oppor- 
tunity of showing this. A young nobleman, from disease, had the heart 
exposed so that it could even be handled while beating; and Hervey found, 
to his astonishment, that, unless his fingers came in contact with the 
245. What is the amount of blood circulated each hour ? 
246. How is the pulse produced ? Upon what does its rapidity depend, and 
to what account is it put ? OF THE CIRCULATION". 
247. When a vein is severed, the walls easily collapse 
and a coagulnm forms around the orifice and checks the 
loss of blood. But when an artery is severed, the elasticity 
prevents its collapsing, and the blood escapes in spirts. 
The loss of blood is often so rapid that it causes death in 
a short time. The first thing to be done then is, to close 
the artery mechanically till surgical aid can be obtained. 
Sometimes the thumb pressed hard upon an artery on the 
side of the wound, toward the heart, will be sufficient to 
check the blood. A handkerchief or other bandage may 
he placed around a limb which has been wounded, and 
drawn so closely that the pressure of a knot in it placed 
over the artery will be sufficient compression. Or a key 
slipped under the bandage and upon the artery may be 
used as a lever to compress the artery. But it may often 
he necessary to put the finger into the wound, find the end 
of the artery, and compress it there. 
But a physician should, in such cases, always he called 
at once. We may succeed in checking the loss of blood for 
the time being, but the end of the artery must be taken 
up and tied with a ligature, in order to resist the elasticity 
of the artery and force of the circulation long enough for 
the artery to heal. 
The danger to be apprehended from the wounding of 
an artery is sufficiently indicated by the fact, that they lie 
as far below the surface as they can be placed, and are 
outer skin, the young man was altogether unconscious of the heart being 
touched.” Upon reflection, we see that it is entirely unnecessary that it 
should have the sense of feeling. Anything that would reach the heart 
would be likely to produce death, and hence the sense of feeling there 
would be no warning of danger, as it is at the surface. 
247. What practical rule is to be observed when an artery is wounded ? How 
is the bleeding to be stopped ? How is the artery to be ultimately secured ? 184 
OF THE CIRCULATION-. 
otherwise guarded in various ways to protect them from 
injury. They are placed so near the surface that the 
pulse can be felt, only when it is impossible to have them 
lie deeper, as those on the head, or those which pass the 
wrist to go to the fingers. 
248. When an artery has been severed, it might seem 
that the circulation in the part to which the artery is sent 
must be prevented. But provision is made for such cases 
by the anastomosing of the arteries. Thus, if the princi- 
pal artery of the arm or leg were taken up (at 9 or 10, pi. 
YL), the small anastomosing arteries (11 or 12) would still 
carry blood to the part beyond, and they would soon en- 
large so as to furnish a competent supply. 
249. The blood is subject to two distinct circulations, 
one through the lungs, which may be called the pulmonary 
circulation, the object of which is to effect certain changes 
in its constitution; and another, much more extensive, 
through the various parts of the body. The object of this 
is the nutrition of the system, and may be called the nu- 
tritive circulation. 
250. The amount of the change effected by nutrition 
is greater than is generally supposed. The quantity of 
food taken is no measure of it whatever. The various se- 
cretions into the joints, the cranium, the abdomen, the 
stomach, and other parts of the digestive canal, as well 
as throughout the solid parts of the body, are generally 
regarded as secretions directly from the blood; but it is 
by no means certain that they are not produced by the 
248. When an artery has been severed, how is the circulation beyond that 
point continued ? 
249. What are the two circulations to which the blood is subject ? 
250. Why is the amount of nutrition not measured by the amount of nutri- 
ment contained in the food? What idea of the amount of repairing done in the 
system do we get from the amount and character of the fluid circulated ? How 
often does the body undergo an entire change ? OF THE CIRCULATION-. 
185 
metamorphosis of the tissues. It is at least certain that 
in various parts of the system there are portions of the 
tissues which lose their vitality, but which have not, by so 
doing, been rendered henceforth useless. On the contrary, 
they go either directly into the blood, through the absorb- 
ent system, or they are passed into the digestive canal, 
to be re-digested and sent again into the circulation. The 
amount of nutritive substance in the food which is eaten 
daily, is only equal to the amount of material which has 
been subject to such changes that it cannot be used again, 
and which, therefore, needs to be rejected from the system 
and have its place supplied by new material. 
Some idea of the amount of taking down and building 
up which is done in the system may be gathered from the 
amount of blood which traverses the blood-vessels, which 
is not less than six tons a day. Its color has been changed, 
and the chemical constitution has been modified to an 
appreciable extent by materials which have been added 
to it from the wear of the system. But the amount of 
removal has been at least equalled by the amount of new 
structure erected. 
Hence we see that our bodies are being taken down and 
built up; that is, they are subjected to change very rap- 
idly. The bones, cartilages, ligaments, and tendons change 
much less rapidly than the soft parts; yet the body has 
probably been wholly taken down and rebuilt several 
times before a person reaches the age of twenty years.70 
251. This process of nutrition takes place wholly in the 
7U It has been thought that the body undergoes an entire change once 
in about seven years. Some parts are, however, changed hundreds of 
times within that period, and possibly some particles may never be 
changed; the change in the more solid parts must also be much more 
rapid in early than in advanced life. 
251. Where does nutrition take place? How are these capillary vessels 
proved to exist To what variation are they subject ? 186 
OP THE CIRCULATION. 
capillary system; that is, in those minute tubes, too 
minute to be traced by the eye, which go from the ex- 
tremities of the arteries to the commencement of the 
veins. Such a connection is proved to exist, by the fact 
that the veins can be filled with mercury by injection 
through the arteries. Though the diameter of these tubes 
cannot be measured, yet we know that it is subject to con- 
siderable variation, and that their size in a great degree 
atfects nutrition. Thus the enlivening emotions at once 
manifest themselves by the flush on the face ; that is, by 
the enlargement of the capillaries to such a size that they 
will admit the red cells of the blood. Fear and other de- 
pressing emotions at once contract the capillaries, pro- 
ducing paleness, and nutrition is almost wholly suspended. 
It is likewise, in a great measure, suspended by exposure 
of the surface to a disagreeable or painful degree of cold. 
The capillaries may become so much enlarged as to con- 
stitute disease (inflammation). Cold water, or other cold 
applications, tend to reduce inflammation, because they 
tend to contract the capillaries. 
252. Wherever growth is required, or waste has taken 
place, there the proper elements are taken from the blood 
in its passage through the capillaries, and deposited for 
the purpose of increase or repair. The selection of ele- 
ments from the blood adapted to the formation of par- 
ticular tissues, their removal from the capillary vessels, and 
their incorporation into the different organs, cannot be ex- 
plained upon any known physical principles. These pro- 
cesses are, however, going on constantly and with rapidity; 
and yet, as a general rule, all this is done without mistake 
as to place, or to the kind or the amount of repairs re- 
quired. We can only refer these changes to the constant, 
252. What are the throe processes In which nutrition consists? Upon what 
principle are these processes explained ? To what must they be referred ? OF RESPIRATION. 
187 
efficient, and beneficent presence of an unseen and divine 
Power. 
CHAPTER III.—OF RESPIRATION. 
253. The respiratory functions are performed principally 
in the thorax. We have seen that there is a vertical par- 
tition stretched between the spine and the sternum, called 
the mediastinum, which divides the thorax into two cham- 
bers (Fig. 98). The membrane which forms the medias- 
tinum also extends round the sides of the thorax, forming 
a complete lining (2, 2) to each chamber, and is then re- 
flected over the surface (3, 3) of the lung. It is called the 
pleura. 
254. The organs of respiration are, the larynx, trachea, 
and lungs. The larynx (Fig. 102) is composed of five 
Fig. 102. 
rig. 103. 
1 The front part of the larynx. 4 The 
posterior part of the cricoid cartilage. 
5, 5 The arytenoid cartilages. 6. 6 
The vocal cords. 9 The attachment 
of the cords to the arytenoid carti- 
lages. 8, 10 The aperture called the 
glottis. 
The Cartilages of the Larynx, c h 
The cricoid cartilage, g The ary- 
tenoid cartilages, t The thyroid 
cartilage. 
Chapter III.—253. Describe the pleura. 
254. What are the organs of respiration ? Describe the several cartilage" of 
the larynx. The vocal cords. Dow is the voice produced ? Upon what do us 
modifications depend ? 188 
OF KESPIKATIOK. 
cartilages. The lowest is a circular ring (c, li), called 
the cricoid cartilage. The thyroid cartilage (t) consists 
of two parts, united at an acute angle so as to form the 
prominent point in the neck (called Adam’s apple). This 
cartilage is situated above the cricoid, so that in front 
there is a membranous space between them.71 But as the 
two parts of the thyroid extend backward, they also be- 
come prolonged downward, so as to inclose the cricoid 
at the sides where they articulate with it. The cricoid is 
widened behind, and upon the upper edge of this widened 
portion (h, h) are placed the two arytenoid cartilages (g). 
From the base of the arytenoid cartilages (5, 5, Fig. 103) 
ligaments (6, 6) called the inferior vocal cords stretch 
forward to the front angle of the 
thyroid cartilage, reducing the di- 
mensions of the tube, and giving 
the aperture a triangular form. 
There are two ligaments com- 
mencing near the top of the ary- 
tenoid cartilages, and running par- 
allel with the lower ones, which are 
the superior vocal cords. A vertical 
section of the larynx, from a to h, 
Fig. 103, would be represented by 
Fig. 104, in which 1, 1 are the su- 
perior, and 2, 2 are the inferior 
cords, and 4, 4 are the ventricles 
of the larynx. The arytenoid car- 
tilages are so furnished with muscles 
that they are capable of considerable motion ; and, as one 
end of the cords 2, 2 is attached to them, it follows that 
Fig. 104. 
1,1 The upper vocal cords. 
2, 2 The lower vocal cords. 
3, 3 The glottis. 4, 4 The 
ventricles of the larynx. 
71 This small membranous space can be felt below the Adam’s apple, in 
the front of the neck, and thus the position of both the thyroid and cricoid 
cartilages will be ascertained. OF RESPIRATION. 
189 
they may be made tight or loose, or be made to approach 
or recede from each other. The voice is made by the air 
from the lungs passing these cords, and its variations of 
tone depend on their adjustment. But it is subject to 
various modifications, from the capacity of the lungs, the 
force with which the air is emitted, from the form and 
size of the mouth, from the nose, the lips, the tongue, the 
teeth, etc. The tube thus formed is suspended from the 
os hyoides (u, Fig. 105) by a membrane, 
n. The fifth cartilage of the larynx (i) 
is the epiglottis, so placed as to fit like a 
lid over the opening between the superior 
vocal cords during deglutition, and pre- 
vent food from entering the larynx. 
Fig. 105. 
255. The trachea (4, pi. III.) is the 
continuation of the larynx to the thorax. 
It is composed of from sixteen to twenty 
rings of cartilage, which, however, do not 
extend entirely around the trachea, but 
leave a space behind, which is closed by 
membrane, and the rings are also attached 
to each other by membrane. Immediately 
behind the first bone of the sternum, the 
The Larynx, i The 
epiglottis, u The 
hyoid bone. I The 
thyroid cartilages. 
n The membrane 
extending from the 
hyoid bone to the 
thyroid cartilage. 
trachea divides into two branches (5, 6) called bronchi, 
which go to the two lungs. 
256. The lungs (1,1, 2, 2, pi. III.) are situated in the two 
cavities of the thorax. The left lung is composed of two 
lobes, and the right lung of three. Each lobe consists of 
a great number of divisions, called lobules. Each lobule 
is a congeries of air-cells, consisting of very delicate cellu- 
lar membrane. The bronchi, after entering the lungs, 
divide into small tubes, and one of these tubes opens into 
255. Describe the trachea. 
256. The lungs. 190 
OF RESPIRATION-. 
each lobule. All of the air-cells in a lobule communicate 
with each other, but there is no communication between 
the air-cells of different lobules. 
257. We have seen that the blood is subject to two dis- 
tinct circulations, one of which is through the lungs. It 
reaches the lungs by the pulmonary artery, which is sub- 
jected to exceedingly minute division, and finally becomes 
a system of capillary vessels, which are distributed upon 
the membranes composing the air-cells. (13, lith. pi. III.) 
The pulmonary veins receive the blood from these capil- 
laries and convey it back to the heart. The lungs are, 
therefore, composed of air-cells, bronchial tubes, arteries, 
and veins.72 
258. Respiration consists in receiving air into the lungs, 
and expelling it from them. This is effected by the alter- 
nate contraction and enlargement of the cavity of the 
thorax; and this change is performed by appropriate 
muscles, and not by any power belonging to the lungs. 
The thorax may be enlarged in three directions. The 
,2 The parts of the lungs here described are those upon which the res- 
piratory functions depend. In addition, the lungs, like all other parts of 
the body, have their nerves, absorbents, and blood-vessels for nutrition. 
The interior surface of all the bronchial tubes and of the air-cells is also 
lined with a mucous membrane, which becomes important from its ex- 
treme liability to take on disease. In a condition of health, the secretion 
from this membrane is only sufficient to keep the surfaces moist, and is 
constantly removed by evaporation. But when inflammation sets in, the 
secretion becomes copious, and cither frothy or thick and adhesive, accord- 
ing to the stage and degree of the inflammation, and is thrown off by ex- 
pectoration. The intensity of the inflammation may vary from that of 
the slightest cold to that of active suppuration. 
257. The pulmonary capillaries. Of what are the lungs composed ? 
258. In what does respiration consist? How is this effected? How is the 
vertical measure of the thorax increased ? The transverse diameter ? The dis- 
tance from the spine to the sternum ? What are the means of ordinary, and what 
of labored, respiration ? OF RESPIRATION. 
191 
diaphragm has the form of a compressed dome (4, 4, Fig. 
106), and the contraction of its fibres tends to depress the 
dome, and reduce its position to 2, 2. The depth of the 
Fig. 106. 
A Front View of the Thorax in Respiration. Air is drawn into the lungs by the 
compression of the diaphragm to the line 2, 2. At the same time the sides of 
the thorax take the position 1, 5. Air is expelled from the lungs by diminish- 
ing the cavity of the thorax. This is effected in part by compressing the sides 
to the dotted line 3, 4. In part, also, by compressing the abdomen from 6 to 7, 
thus elevating the stomach and liver, and lifting the diaphragm to the dotted 
line 4, 4. 
thorax is thus increased. The ribs come obliquely for- 
ward and downward from the spine, so that their anterior 
extremities meet the line 2, 2, Fig. 107. There are several 
sets of muscles (8, 8) so attached to the ribs, that their 
contraction will raise them to a position nearly horizontal, 
and their extremities will be brought forward to the line 
3, 3; that is, the transverse diameter of the thorax will 192 
OF RESPIRATION". 
be increased. The sides of the thorax will then have the 
position 1, 5, Fig. 106, instead of 3, 4. At the same time 
the sternum will be thrown forward, so as to occupy the 
Fig. 107, 
Fig. 108. 
1,1 The ribs. 2. 2 The sternum in 
the position which it takes in ex- 
piration. The ribs are raised 
during inspiration, so that the 
sternum is brought forward to 3, 
3. 4, 4 The spine. 8, 8 Muscles 
by which the ribs are raised at 
inspiration. 
Side View of the Thorax. 1 The 
cavity of the thorax. 2 The cavity 
of the abdomen. 3 and 4 The dif- 
ferent positions of the diaphragm in 
expiration and inspiration. 6, 6 and 
7, 7 The different positions of the 
sternum and abdomen 
position 7, 7, Fig. 108, instead of 6, 6, which it does when 
the thorax is contracted. 
In ordinary respiration, the diaphragm is the principal 
agent.73 But in forced respiration, nearly all of the mus- 
cles of the neck, thorax, and abdomen are employed. 
,3 This action of the diaphragm is intimately connected with digestion. 
The depression of this muscle can take place only as the muscles of the 
abdomen are relaxed, to make room for the abdominal viscera; hence the OF RESPIRATION. 
193 
259. The amount of air received into the lungs at each 
inspiration is about one pint. But this will vary at differ- 
ent times in the same individual. Thus, vigorous exercise 
induces much fuller inspirations than are needed when we 
are at rest. The danger ordinarily is, that the amount 
will be below the wants of the system. This may result 
from the thorax being contracted naturally, or by the 
compression which it has received from the closeness with 
which clothes are worn, from the habit of sitting or walk- 
ing with the shoulders bent over and resting upon the 
thorax, or from a diseased condition of the lungs. 
260. Mental states also have an influence upon the 
amount of respiration. Depression of spirits diminishes 
the action of the respiratory muscles ; and hence the deep 
inspirations {sighing) to which such persons are accus- 
difficnlty of breathing.after a hearty dinner, when all of the relaxation 
of the muscles is required to make room for the distension of the stomach. 
The diaphragm rises in consequence of the contraction of the abdomi- 
nal muscles pressing the viscera upward against it. Thus, the process 
of respiration cannot be carried on at all without giving constantly to the 
stomach and intestines the motion upon which the digestive process in a 
great measure depends. 
It should not be inferred that ordinarily there is no elevation and de- 
pression of the ribs in respiration, for every person can see, by observing 
his own breathing, that there is. Still the object of this means of respi- 
ration seems specially designed to supply an extra amount, cither when, 
from active or fatiguing exercise, the system demands an increased influ- 
ence from respiration, or when, from the air being less pure, a greater 
amount is needed. Hence, persons who receive a sufficient supply, when 
the air is pure, become faint on entering a crowded room, if they are so 
dressed that their respiration cannot, by the movement of the ribs, be in- 
creased. 
259. What amount of air is ordinarily received into the lungs? Upon what 
does the variation from this amount depend ? 
260. How do the states of mind affect the amount of respiration ? What is 
the physiology of yawning ? 194 
OF RESPIRATION”. 
tomed. Nature thus insists upon these deep inspirations 
occasionally, to prevent in part the evils which would 
otherwise arise from the too limited amount of air which 
the lungs are receiving. 
Yawning is for a similar purpose. It generally occurs 
either in the morning, before the respiratory muscles have 
received the amount of stimulus which, in a waking state, 
they need, or at other times when the body is sluggish and 
the respiratory action is feeble. It consists of an involun- 
tary, deep, and prolonged inspiration, in order to com- 
pletely fill the lungs, and furnish the necessary stimulus 
when a person is not disposed to secure it by active ex- 
ercise. 
261. The object for which air is introduced into the 
lungs is to supply oxygen to the blood. But if pure oxy- 
gen is breathed, the stimulus is too great. The atmosphere 
which has been provided for our use in respiration contains 
one-fifth of its volume of oxygen, and the most of the re- 
maining four-fifths is nitrogen, which, so far as is yet 
known, has no other end than to dilute the oxygen so as 
to adapt it to the purposes of the system. 
Assuming that the oxygen contained in a pint of air at 
the ordinary temperature, is the amount needed by the 
blood at each inspiration, it is obvious that when the air 
is reduced in volume by cold, a pint will contain more than 
we are supposed to need ; and when it becomes expanded 
by a high temperature, it will contain less. The quantity 
of oxygen received into the lungs may vary from this 
cause by as much as one-fourth of the whole amount. 
As the consumption of oxygen is connected with the 
development of the vital force, we see in this a reason 
261. For what purpose is the air received into the lungs ? What, is the con- 
stitution of atmospheric air ? To what extent may changes of temperature vary 
the amount of oxygen inhaled ? Why is more energy of the system experienced 
and more animal heat developed in winter than in summer ? OF RESPIRATION. 
why we should, in winter, experience more elasticity of 
feeling, possess more energy, and be able to perform more 
labor. Vital heat is also developed in connection with the 
consumption of oxygen. As a larger amount of heat is 
needed by the system in winter than in summer, it is a 
wise provision that a larger amount of oxygen is then 
necessarily inhaled. 
262. The air may lose, to some extent, its fitness for res- 
piration by being diluted with other substances, such, for 
instance, as watery vapor, but especially by carbonic acid. 
A very small proportion of carbonic acid, about a tenth 
of one per cent., always exists in the air, and does not ap- 
pear to be injurious; but, in various Avays, it is liable to 
accumulate in larger quantity, chiefly, however, by respi- 
ration. If, by means of a tube, we breathe into a trans- 
parent solution of lime, it will at once become milky, and 
a chalky substance will at length subside. This, like com- 
mon limestone or chalk, is carbonate of lime, of which the 
lime was dissolved in the water, and the carbonic acid 
must have come from the lungs. It is one of the essen- 
tial products of respiration. It is injurious, not simply 
because it dilutes the air, and thus diminishes the propor- 
tion of free oxygen, for even Avhen oxygen is added arti- 
ficially, the presence of carbonic acid renders it detrimental. 
Four per cent, of this gas, which is about the proportion 
contained in the air as it comes from the lungs, renders 
it highly injurious, and a much smaller proportion is un- 
doubtedly hurtful. In this fact principally consists the 
importance of proper ventilation of school-houses, work- 
262. How may the air lose, to some extent, its fitness for respiration ? How 
is it shown that carbonic acid is exhaled from the lungs ? What proportion of 
carbonic acid does the exhaled air contain ? Does the injury to the air from the 
presence of carbonic acid arise from its reducing the amount of free oxygen? 
Why should places in which many persons are likely to be collected be well ven- 
tilated ? 196 
OF RESPIRATION. 
shops, churches, • halls for public meetings, and sleeping 
apartments.74 
263. The air is received into the air-cells (4, 4 pi. IV., 
Fig. 2) in the lungs, and the blood flows through the 
blood-vessels which are spread out over the surface of these 
cells. There is, therefore, a membranous partition between 
the blood and the air. Membrane is not, however, as was 
formerly supposed, impermeable to air, or even to liquids; 
but some gaseous substances penetrate it much more 
readily than others. Oxygen, carbonic acid, and watery 
vapor are found to be of the first kind, while nitrogen 
scarcely passes through membrane at all. It follows that, 
when atmospheric air is received into the lungs, the oxy- 
gen will readily pass from the air-cells into the blood, 
74 The sleeping apartment has sometimes been warmed by setting a 
dish of burning charcoal within it. The casualties arising from this prac- 
tice have, it is hoped, put an end to it. It is obvious that it must be at- 
tended with great danger, for carbonic acid is rapidly given off from burn- 
ing charcoal, and the danger is increased from the fact that this gas tends 
to produce stupidity and sleep, and therefore furnishes to the individual 
no warning of its effects. 
The large fireplace and chimney of former times had its advantages; 
for, with a good draught, the amount of air carried from a room by it 
was always sufficient to accomplish all of the purposes of ventilation. 
When the draught is imperfect, carbonic acid may be thrown from a 
grate of ignited coal into a room in such quantity as, without producing 
any smoke, to bring on headache, and make the air very unwholesome. 
The use of air-tight stoves has this disadvantage, that they effect no 
change of air in a room. They can be safe only when the air is frequently 
changed by opening doors or windows. 
The objection to ventilation is, that in cold weather it introduces cold 
air, and with it exposure to cold. This objection is obviated in the use 
of furnaces. The air should be allowed to escape at the top of the room, 
and the air which is admitted is that upon which the warmth of the room 
depends. 
263. How does the oxygen reach the blood in the lungs ? Why does not the 
nitrogen also enter the circulation 7 OF RESPIRATION. 
197 
while the nitrogen will he retained, and that carbonic acid 
and watery vapor will easily pass from the blood into the 
air-cells and be expired. 
264. There are about twenty respiratory movements in 
a minute, and one pint of atmospheric air is inhaled each 
time. One-fifth of the atmosphere is oxygen; and it is 
found that about one-fourth of the oxygen, that is, one- 
twentieth of the whole amount of inspired air, disappears 
at each respiration, and nearly an equal volume of carbonic 
acid is supplied. By twenty respiratory movements, then, 
that is, every minute, a pint of oxygen is received into the 
circulation, and during the same time nine pints of blood 
(245) have circulated through the lungs. The blood, 
therefore, absorbs one-ninth of its volume of oxygen from 
the atmosphere. 
265. We may now inquire what are the changes in the 
constitution of the blood effected by respiration ? We 
have seen that the blood which comes to the lungs has a 
dark-red or purple color (243), and that when it goes from 
the lungs it has acquired a scarlet hue. In the lungs, the 
blood parts with carbonic acid and absorbs oxygen. These 
are all of the changes of importance known to occur; and 
we might infer that in these changes consists the conver- 
sion of venous to arterial blood. We can, however, subject 
venous blood to more direct experiment, by taking it from 
the system and exposing it to the action of the atmosphere, 
under such circumstances as to exclude the influence of 
other causes. It is still found to take the color of arterial 
blood, while oxygen is absorbed and carbonic acid is given 
off. The blood seems to undergo no change in chemical 
264. What proportion of its volume of oxygen does the blood take up? 
Give the calculation upon which this statement is made. 
265. What changes does the blood undergo in the pulmonary capillaries by 
resp. ration ? How may the proof be given out of the body ? What changes take 
place in the nutritive capillaries ? 198 
OF RESPIRATION'. 
constitution after leaving the pulmonary capillaries, till it 
reaches the nutritive capillaries, and none after it enters 
the veins till it reaches the lungs. Hence, the changes 
which take place in the nutritive capillaries must be ex- 
actly the reverse of those in the lungs; that is, the blood 
must part with oxygen and absorb carbonic acid. 
266. The blood contains a small proportion of iron, 
amounting in the whole system to one or two ounces. 
This is found in the blood-cells. The most satisfactory 
explanation of these changes (which is, however, to a great 
extent hypothetical) consists in supposing that in the ar- 
terial blood the iron is in the state of a peroxide; that is, 
it is combined with one equivalent and a half of oxygen. 
In its circulation through the nutritive capillaries it meets 
with carbon, with which half an equivalent of its oxygen 
combines, forming carbonic acid. The iron is then re- 
duced to the state of a protoxide. The carbonic acid 
combines with the protoxide, forming a carbonate of the 
protoxide of iron. This carbonate gives to the blood its 
venous character, and as such it leaves the capillaries and 
enters the veins. When the blood reaches the lungs, the 
oxygen there received decomposes this carbonate, sets the 
carbonic acid free, which escapes in respiration, and com- 
bines with the iron, restoring it again to the state of a 
peroxide. If this view is correct, the office of the blood- 
cells is that of carriers, distributing the oxygen from the 
lungs to every part of the body to which the circulating 
fluid is sent, and gathering up the refuse carbon and con- 
veying it to the lungs to be eliminated. 
267. It remains to determine the purposes for which 
these changes take place. 
266. Give the changes which are supposed to take place in the blood-cells. 
267. What is meant by the vital force 1 Why can this not be considered as 
some other known force (as electricity, for example) acting to prevent the chemi- 
cal changes? OF RESPIRATION'. 
199 
The nutritious substances are highly complex com- 
pounds, such as are produced only by the processes of 
vegetable life, and are held together by a very feeble 
affinity. Whenever they become deprived of life, decom- 
position at once begins. We see this in the spontaneous 
decay of meats, fruits, vegetables, and even wood. But as 
long as they possess vitality, there is a power which resists 
this tendency to decay. We cannot make use of any other 
known power, such as heat, electricity, cohesion, or gravi- 
tation, to produce these results. We therefore give it a 
distinct designation—the vital force. 
268. We have seen that, at short intervals, a certain 
amount of nutritious substance must be supplied to the 
blood. Before it enters the system, it is identical in com- 
position with living tissue.75 It therefore brings into the 
system the force by which it retains its complex composi- 
tion. It passes without change of chemical constitution 
through the digestive apparatus, and through the organs 
of circulation. In the nutritive capillaries, it is simply 
removed from the circulation and incorporated into mus- 
cular and other tissues. The first change in the consti- 
tution of the nutritious substance takes place in the nu- 
tritive capillaries, by the combination of the oxygen which 
the blood-cells convey with the carbon of the living tissues. 
We must conclude, then, that this current of oxygen which 
enters the system by respiration, has for its object the 
decomposition (the destruction of vitality) of parts of the 
living body. 
75 It is not intended to convey the idea that the several tissues, such as 
muscle, membrane, cartilage, nerve, and brain, are identical in composi- 
tion ; but so nearly identical that, in order to give a correct general view of 
the several vital processes, they may be so considered. 
268. What change is effected in the nutritive capillaries by the oxygen of the 
blood-cells ? How does the vital force become available ? How is it used ? 
What part of it can be employed in voluntary effort f 200 
OF RESPIRATION". 
But when this decomposition takes place, it liberates the 
vital force by which the combination was before retained. 
And this force, no longer employed in the service of the 
nutritions substance, now becomes available for other 
purposes. The system claims the involuntary motions, 
such as those of nutrition, respiration, digestion, the con- 
traction of the heart, etc. ; and the brain controls and 
appropriates enough force for this purpose, whether we 
assent to it or not. The surplus of this force we are at 
liberty to employ in thought, exercise, labor, etc., at our 
option. This is a man’s physical strength. 
269. This explanation of the mechanical power of the 
system is in accordance with all of the known facts which 
bear upon it. 
Thus, if a person breathes impure air, or has a con- 
tracted chest, so that but a limited amount of oxygen is 
inhaled, but little tissue can be decomposed, and his mus- 
cular powers are in the same proportion enfeebled. 
If a person be confined to a scanty diet, but little living 
tissue will be formed. But little, therefore, can be decom- 
posed, and his ability to perform physical labor is corre- 
spondingly reduced. 
When a person puts forth an extraordinary degree of 
muscular effort, a large amount of decomposition must 
take place, and a large amount of nutrition is required. 
Hence it is, that whenever an unusual amount of muscu- 
lar effort is demanded, the respiratory effort is increased, 
and the amount of air inhaled is increased two or three 
fold. The immediate effect is the increased decomposition 
of living tissue and the increased supply of physical power. 
269. "What is the effect of limited supply of oxygen, and why ? What of lim- 
ited supply of food, and why ? What conditions are necessary where great mus- 
cular effort is required ? What is the effect of rapid growth upon the strength, 
and why ? In what consists the demand for sleep ? How docs vitality cease from 
starvation ? OF RESPIRATION 
201 
A large amount of nutriment may be taken into the 
system, but may be used principally to promote growth. 
As there is but a small proportion of it decomposed, there 
is but little muscular power or ability to endure fatigue. 
It would seem that the system is incapable of renewing 
these tissues as rapidly as they are decomposed by the sys- 
tem in an active condition. Hence it is made necessary 
that most of the mechanical functions should be periodically 
suspended, and respiration become less active. This is 
the period of sleep, and only so much mechanical force 
is employed as is necessary to carry on the circulation and 
reconstruct the tissues in which the decomposition was 
becoming excessive. 
When the decomposition of tissue goes on, and furnishes 
the force necessary to perform the vital functions, and there 
is no supply of food from which new tissue can be formed, 
extreme emaciation takes place. When there is no tissue 
left which is capable of decomposition, the vital force can 
no longer be developed, and life no longer exist; such is 
death by starvation. 
270. We have seen that one effect of the combination of 
oxygen with these tissues is, to convert the vital force into 
available mechanical force. Another effect must be the 
development of heat. The changes are as strictly a com- 
bustion as if they took place in the open air—of precisely 
the same nature as the combustion of ordinary fuel. They 
consist essentially in the combination of oxygen and car- 
bon ; and it is one of the necessary results of this combi- 
nation to generate heat. 
In ordinary combustion carbon is supplied in the form 
of wood or coal; the oxygen is derived from the air; car- 
270. What other effect besides the development of vital force results from 
these chemical changes ? Compare these changes with ordinary combustion. 
How is the amount cf heat limited ? Where is it produced ? OF RESPIRATION. 
bonic acid is formed and removed by the current of air: 
a residual ash of earthy matter with which oxygen will not 
combine is left, and heat is evolved. Within the system, 
the fuel is the living tissue, the oxygen is furnished by the 
red blood-cells; carbonic acid is produced by the combina- 
tion, removed by the venous blood, and at length exhaled 
from the lungs; a residual substance with which oxygen 
will not combine is dissolved in the blood, but finally re- 
moved by the action of the kidneys, and heat is evolved. 
The amount of heat evolved must be in exact propor- 
tion to the carbon consumed, and depends, therefore, upon 
the amount of oxygen inhaled. The heat will be evolved, 
not in the lungs particularly, but in every part of the sys- 
tem to which the oxygen is carried by the blood-cells. 
271. We have thus far spoken of the food as composed 
of nutritious substances; that is, of substances which are 
identical in composition with the tissues of the body, and 
which, in order to effect the nutrition of the system, need 
only be rendered soluble by the digestive process, intro- 
duced into the circulating fluid, and appropriated to the 
repairs and growth of the several parts. All of these sub- 
stances consist essentially of four elements—oxygen, hydro- 
gen, carbon, and nitrogen.78 They are called the ele- 
ments of nutrition, or, as they are characterized by 
containing nitrogen, they may be called the nitrogenized 
constituents of the food. 
The flesh of animals, cheese, and eggs consist almost 
76 There are various other substances, such as soda, potassa, lime, phos- 
phorus, sulphur, and iron, in very small quantities, in the elements of 
nutrition. 
271. What are the two kinds of food ? What is the relation of the elements 
of nutrition to the living tissues ? What is their composition ? How are they 
characterized ? What are examples of this kiud of food 1 What do the elements 
of nutrition accomplish in the system f OF RESPIRATION. 
203 
entirely of these elements. The albuminous vegetables, 
such as beans, peas, etc., and the gluten of wheat and 
other grains, contain them in large proportion. Most other 
vegetable substances — the grasses, roots, etc. — contain 
them, but in smaller proportion. 
The living tissues are built up from these elements, 
and by the decomposition of these tissues and their elim- 
ination, the forces of the system and animal heat are de- 
veloped. 
272. If the amount of heat required were in all cases 
exactly proportioned to the vital force required, and if the 
oxygen present were no more than sufficient to combine 
with the tissues for the production of this force, there 
would be no occasion for any other kinds of food. This, 
however, is by no means the case. A part of the year we 
are surrounded by a temperature little inferior to that of 
the body. But little animal heat is lost, and the supply 
required is very small, though the amount of vital force 
required be considerable. In the winter season the radia- 
tion of heat from the body is very rapid; and, in order to 
sustain the requisite temperature, heat must be rapidly de- 
veloped by the system, even though but little vital force 
is needed. Moreover, if there were an excess of oxygen 
in the circulation, it would probably continue to combine 
with the living tissue, and produce emaciation and disease. 
Hence the necessity of food which has a composition so 
different from living tissues that it cannot become a part 
of them. Of this description are the oils, the fat of ani- 
mals, sugar, starch, and all of the saccharine and farina- 
ceous parts of the grains, roots, grasses, and whatever 
vegetable substances are ever used as food. They are 
272■ Under what circumstances may we suppose no other kinds of food would 
he necessary ? What are the circumstances which render another kind of food 
necessary ? What are instances of this second kind ? What is their composi- 
tion ? What are they called ‘t How are they eliminated from the system ? 204 
OF RESPIRATION". 
composed of oxygen, hydrogen, and carbon, but contain no 
nitrogen, and are called the elements of respiration. 
The oxygen and enough of the hydrogen to constitute 
water, will not affect the temperature of the body. The 
excess of the hydrogen and the whole of the carbon may 
combine with the oxygen of the inspired air. This com- 
bination must develop heat in proportion to the amount 
consumed. The products, after combination, are only car- 
bonic acid and water, both of which are given off in large 
quantity by the lungs. 
273. It follows, in the first place, from the different pur- 
poses to which the elements of nutrition and those of 
respiration are subservient, that all persons, and in all 
circumstances, require some food which contains the ele- 
ments of nutrition, and that persons of sedentary habits 
need less of these elements than those whose occupations 
require the exertion of more physical force. 
Secondly. The kind and amount of food should vary 
with the season and the climate. The inhabitants of warm 
climates eat less than those of cold, both because they 
need to develop less animal heat, and because they put 
forth less physical effort. Every person needs more of the 
elements of respiration in his food in winter than in sum- 
mer. In the extreme northern regions, the inhabitants 
consume large quantities of fat, oil, and other substances 
which contain no nitrogen, but which are rich in carbon.77 
77 With persons who indulge in free living, and who exercise but liltle, 
the oxygen received into the system is insufficient to consume entirely the 
carbon which belongs to the tissues, offered for decomposition. These 
tissues are decomposed, but the residuum is a nitrogen compound contain- 
27 3. Why do all persons need the elements of nutrition? Do sedentary or 
active persons need the most, and why ? From what sources, animal or vege- 
table, are these to be obtained ? What effect should the seasons have in the 
selection of food ? Why is less food needed in warm climates ? What is ihe 
character of the food among the inhabitants of the polar regions, and why? OF ABSORPTION. 
205 
If there is an excess of these elements of respiration in 
the system, it is deoosited in the form of fat.78 
CHAPTER IY.—OE ABSORPTION. 
274. The lacteals are a part of the absorbent system, 
designed for the absorption of the chyle from the small 
intestine, and have been described in connection with the 
subject of digestion. 
275. The veins are also absorbents. Most of the ab- 
sorption of the system is undoubtedly performed by them; 
for the sixty gallons of blood which they return to the 
heart every hour is sufficiently charged with absorbed mat- 
ter to change sensibly its properties. It is one special 
function of the veins to absorb from the stomach the nit- 
rogenized elements of the food. Another office of the 
veins, as absorbents, is to take up the waste products oc- 
casioned by the decomposition of the living tissues. 
276. There is a third class of absorbents, called lym- 
phatic vessels. (Figs. 109, 110, 111.) They commence 
by a network of exceedingly minute tubes in all parts of the 
ing an excess of carbon, and in consequence becomes insoluble. It often 
accumulates in the bladder as stone or gravel, and can be removed only 
by surgical operations. 
78 Advantage is taken of this in the fattening of domestic animals. 
They are furnished with an abundance of such food as is readily trans- 
formed into fat: that is, of the elements of respiration. To secure these 
elements from being removed by respiration, every precaution is taken to 
diminish the quantity of oxygen received into the system, by preventing 
exercise, and by guarding them against exposure to a low temperature. 
Chapter IV.—274. What is the office of the lacteals ? 
275. What is the office of the veins, as absorbents ? 
276. What is the third class of absorbents ? Describe them. 206 
OF ABSOKPTIOFT. 
Fig. 109. 
A Lymphatic Vessel, magnified. 
surface of the true skin, and of all the free surfaces, such as 
the membranes which invest the brain, and the serous 
Fig. no. 
A Lymphatic Vessel laid open to show the valves 
membranes generally, the mucous and synovial membranes, 
the surface of the eye, and the interior surface of the arteries 
Fig. Ill 
Lymphatic Vessels passing through glands. 
and veins. The network of these is so close (Fig. 112) 
that when injected, the surface looks like a pellicle of 
quicksilver. As they leave the 
surfaces in which they origin- 
ate, they are still slender tubes, 
but abundantly supplied with 
valves, occasionally passing 
through glands, and, though 
not uniting into large tubes 
like the veins, they converge 
toward the centre of the sys- 
tem, and finally unite in the thoracic duct. (Fig. 113.) 
A Plexus of Lymphatic Vessels in the 
skin, magnified. OF ABSORPTION. 
277. In all parts of the body there are substances which 
have performed the offices for which they were intended, 
and, being no longer useful, require removal. Of this na- 
ture are the secretions within the joints, thorax, abdomen, 
and cranium. In like manner, particles of the body, 
either from its ordinary motions or from accident, as in 
case of bruises, extravasation of blood, etc., are continually 
losing their vitality, and need to be removed. The re- 
moval of such substances seems to be specially the duty of 
the lymphatic vessels. 
278. These vessels are found to contain a liquid gener- 
ally colorless and somewhat resembling the serum of the 
blood. It is mingled with the chyle in the thoracic duct, 
by which this mixed fluid is conveyed into the blood. 
Thus every substance which has once been used, as the 
synovia or any of the lubricating fluids, but which is ca- 
pable of being appropriated again, is returned to the cir- 
culation for that purpose. Whatever is incapable of such 
use will be separated from the blood by some secreting 
process. 
279. Several conditions of the body depend on the ac- 
tivity or inactivity of this system. 
When the absorbents of the head, thorax, abdomen, 
pericardium, or joints fail to absorb the fluids secreted 
into their cavities, dropsy occurs in those parts. 
When the quantity of refuse matter in any part of the 
body is greater than the absorbents can remove, a tumor 
is formed, which increases in size till it opens a passage 
to the surface and the vitiated matter is discharged. 
277. What substances are they intended to absorb ? 
278. Describe the fluid which they convey. What is the object of returning 
It into the blood ? 
279. What is the effect when the absorbents of the closed cavities become 
inactive ? What is the result when the refuse matter becomes considerable ? 
What are eruptive diseases ? 208 
OF SECRETION. 
Eruptive diseases consist in the deposition of such mat- 
ter near the surface of the body as the absorbents will not 
act upon. 
280. These vessels, though they do not reach through the 
cuticle, are yet capable of taking up substances which 
exist on the surface and conveying them into the blood. 
Unguents, poisons, and contagious miasma, as well as mois- 
ture and liquid nutriment, are sometimes in this way con- 
veyed into the circulation. Kefuse and unwholesome 
matter is constantly thrown from the system by perspira- 
tion, and, if not removed by frequent ablutions, will be re- 
absorbed and tend to generate disease. 
CHAPTER V.—OF SECRETION. 
, 281. The secretions of the system have several objects. 
There is one kind of secretion the object of which is to 
lay up in store substances which the system may afterward 
need. The adipose matter, the fat of the system, is such 
a substance. It comes from the elements of respiration. 
When there is a residuum not needed at the time it is fur- 
nished, it is deposited in the cells of the loose cellular tissue, 
for the purpose of being removed whenever the condition 
of the system is such as to need a larger supply of animal 
heat than the daily supply of food will produce. It is this 
store of fat which enables hybernating animals to sustain 
a feeble respiration during the whole winter without taking 
food at all. 
280. What substances are absorbed by these vessels from the surface ? 
Chapter V.—281. What is the object of the secretion of fat ? What is the 
second kind secretion ? The third ? The fourth ? OF SECRETION. 
209 
A second class of secretions is designed to accomplish 
particular objects in the system. When these are accom- 
plished, the secretion is again returned to the circulation. 
Such are the secretions from the serous and some of the 
mucous membranes. 
A third class of secretions are also designed to accom- 
plish special purposes in the system, but having accom- 
plished these purposes, are of no further use. Such are 
the tears, the ear-wax, and the perspiration. 
A fourth kind, of which the urine is perhaps the only 
example, has no other known object except the separation 
of refuse matter from the blood, and the rejection of it 
from the system. 
282. The nature of the secreting process is not 
understood. It has, by some, been regarded as a chemical 
process, by others as a mere filtering process. But the facts 
are inexplicable on either theory. We may consider it as 
a separation of substances from the system, so controlled 
by the vital force as to make the selection always the one 
required, just as the proper selection is made of the mate- 
rials for the growth and repair of the several parts of the 
body.79 
283. The organs of secretion are of two kinds—surfaces 
and glands. Secretion takes place from all the surfaces 
of the body. 
79 An explanation of this process on physical principles would seem to 
be impossible ; it obviously involves something more than mere physical 
agency. There is choice, a function of mind, the work of a thinking 
Being; and yet our thinking powers have no control over it. This Being, 
our Divine Protector, exercises this choice for us without cessation, and in 
all parts of the body. Otherwise our life must cease at once. 
282. What is the nature of the secreting process ? 
283. How many kinds of secreting organs are there ? How are the closed 
cavities lubricated ? What is the secretion from the several parts of the aliment- 
ary canal ? What is the secretion from the lungs ? 210 
OF SECRETION. 
The lining membranes of all the closed cavities, such 
as the joints, thorax, abdomen, cranium, and pericardium, 
secrete fluids to lubricate them. 
The membranes which line the nasal cavities, the mouth, 
pharynx, and esophagus, and the intestines, secrete a mu- 
cous substance for the lubrication and protection of these 
organs. The internal surface of the stomach is a mucous 
surface, but the object of its secretion is particularly the 
digestion of food. 
The internal surface of the lungs secretes carbonic acid 
and watery vapor. Perhaps this ought to be regarded rather 
as transmission of these gases, for the surfaces seem to have 
no more agency in the process than lifeless membrane. 
284. The skin furnishes two kinds of secretion, one 
from follicles and one from perspiratory tubes. The fol- 
licles (Fig. 114) are small cavities situated 
in the substance of the true skin, and 
opening at the surface by narrow orifices. 
They are found in all parts of the surface, 
but are most abundant in the arm-pits, the 
groins, and on the face and nose. They 
furnish an unctuous secretion, which serves 
to soften the cuticle, and probably to prevent it from being 
affected by the dryness or moisture of the atmosphere.80 
They are large on the edges of the eyelids, and the oily 
secretion probably prevents the lachrymal fluid from es- 
caping externally.81 They are also abundant in the ear, 
and produce the ear-wax. 
Fig. 114. 
Simple and Com- 
pound Follicles, 
magnified. 
80 The orifices of the follicles are apt to become closed, and the secretion 
within the enlarged opening becomes hardened, producing a black speck; 
the contents of the follicle can be removed by pressure. These substances, 
from their form and hardness, have been called “ worms.” 
81 The inflammation of these follicles constitutes the “ sty.” 
284. Describe the follicles aud their secretions, and their use. OF SECRETION-. 
211 
Follicles are also found in the mucous surfaces ; but the 
secretions from them are like the secretions from the sur- 
faces in which they are situated. 
285. The most important action of the skin is that of 
perspiration. This function is performed by small 
tubes, which commence below 
the true skin in the perspira- 
tory glands (g, g, Fig. 115). 
These tubes pass by a spiral 
course through the true skin 
and cuticle to the surface. The 
orifices of these tubes are, in 
popular language, the pores of 
the skin. They are very nu- 
merous, amounting in some 
parts of the surface to several 
thousands upon a square inch. 
rig. 115. 
286. One office of these tubes 
is to remove a certain amount 
of refuse substance from the 
system. It is generally in the 
form of insensible perspiration, 
that is, of vapor, which is con- 
tinually escaping from all parts 
of the surface; but in warm 
weather, or during severe exercise, it is abundant enough 
to appear as moisture on the skin, and sometimes in drops. 
The perspiration consists of water slightly charged with 
saline ingredients. The amount of daily perspiration must 
be exceedingly variable; but it is probably about one-fourth 
of the weight of the solid and liquid substances which we 
take into the stomach. 
Section ol the Skin of the Finger, 
magnified fourteen times its thick- 
ness. ff, g The perspiratory glands, 
situated in the cellular tissue, /, 
below the skin, h, h The perspi- 
ratory tubes, passing through the 
several layers of the skin, and 
opening upon the surface, i, i. 
285. Describe the perspiratory apparatus. 
286. What is their office ? How does the perspiration appear ? How much is 
eliminated in this way ? 212 
OF SECRETION. 
287. Another important office of perspiration is its in- 
fluence upon the temperature of the system. We have 
seen that heat is produced by the combustion of the carbon 
of the decomposed tissues, and that provision is made for 
increasing it by furnishing certain kinds of food which 
have no other object. But we often need the means of 
also reducing the heat. We may often be surrounded by 
a temperature equal, or nearly equal, to that of the system. 
Heat will continue to be generated, but there will be none 
radiated. It is the office of perspiration to effect its re- 
moval. Water, at the temperature of the body, must 
absorb eleven hundred degrees of heat in order to be- 
come vapor. For every ounce, therefore, of water given 
off in a state of vapor by perspiration, enough heat has 
been taken from the system to heat seventy pounds of 
water one degree. The apparatus of perspiration has 
thence the power of abstracting heat with great rapidity ; 
and as the temperature rises, the rapidity of perspiration 
increases. So complete is this protection, that a person 
may remain for half an hour in an oven sufficiently heated 
to cook his dinner and not be injured, provided his per- 
spiratory system be in a state of great activity.83 
288. The follicular secretions are not of a nature to be 
83 It is scarcety credible that the human system can endure a tempera- 
ture so high as, in perfectly well authenticated cases, it is known to have 
endured. Sir Charles B lagden and others exposed themselves to a tem- 
perature of 260°, that is, about 50° above the temperature of boiling water, 
without injury, Chantrey, the sculptor, often entered his drying-rooms 
when they were at a temperature of more than 300°. It has been said 
that ovens heated to a temperature of 600° have been entered by some of 
the famous fire-kings, without injury ; but the accuracy of these statements 
may be doubted. 
287. What other office has perspiration ? Why is this necessary ? How does 
it accomplish this object ? 
288. Why is frequent ablution necessary? By what should we be governed OF SECRETION-. 
213 
evaporated, and the saline ingredients of the perspiration 
are also left on the surface. In order that these substances 
may not obstruct the pores of the skin, and that they be 
not absorbed by the lymphatic vessels, it is important that 
the entire surface be washed daily with water and soap, or 
some other similar detergent. The method may be by the 
water bath, vapor bath, by showering or sponging, accord- 
ing to the convenience of each individual. 
Experience must teach us whether warm or cold water 
should be used. If there is a healthy and vigorous reac- 
tion after using cold water, then that is to be preferred 
If the surface becomes shrivelled and pallid by the use 
of it, then warm water is better. And in all cases suffi- 
cient friction upon the surface should be produced by the 
towel or flesh-brush, to restore an energetic circulation. 
Lastly. The clothing and exercise should always be 
such as to preserve the requisite warmth and keep open 
and active the perspiratory orifices. 
289. Secretion from glands. Most of these secre- 
tions are subservient to other functions, and have already 
been described. The principal of these secretions are from 
the lachrymal and salivary glands, and from the liv6r and 
pancreas. 
290. The kidneys (Fig. 116) are two large glands situ- 
ated in the lower part of the abdomen, one on each side 
of the spine. They receive a very large supply of blood, 
and secrete from it the urine, which is conveyed by the 
ureters to the bladder, and is thence expelled from the 
system. 
The importance of this secretion consists in the fact 
in selecting warm or cold water ? What conditions besides cleanliness are ne- 
cessary to the healthful action of the perspiratory system ? 
289. What glands have been before described ? 
290. Describe the kidneys. In what respect are they important ? 214 
OF SECRETION. 
Fig. 116. 
Section of the Kidney. 
that it is the only one by which certain substances can he 
eliminated. The urea, that is, the solid portion, which re- 
mains when urine is evaporated, is derived from the de- 
composition of the tissues, muscle, cartilage, etc. It is the 
nitrogenized compound left when the oxygen of the blood- 
cells has combined with most of the carbon. For the sepa- 
ration of this substance from the blood there is no other 
provision but the kidneys ; and if it were not removed, the 
blood would very soon be incapable of carrying on the 
functions of nutrition. 
291. In addition to the glands above named, there is the 
spleen, situated at the left of the stomach, the office of 
which is supposed to be to receive the blood, during the 
intervals between digestion, which the stomach receives 
while digestion is going on, and thus the constant and in- 
291. What is the situation and use of the spleen ? Of the thymus and thyroid 
glands f OF SECRETION-. 
215 
jurious accumulation of the gastric juice is prevented. 
There are also the thymus and thyroid glands, situ- 
ated in the neck, which are subservient to infantile life, 
probably by receiving and returning the blood which in 
maturer life is sent to the brain. 
292. The healthy action of the secreting organs is of 
the utmost importance. If the urine is not secreted, the 
blood is soon poisoned. When this secretion is too copious 
it becomes a dangerous disease. If the gastric juice is de- 
ficient, digestion ceases. Upon derangement of the biliary 
secretion arise some of the most formidable diseases. If 
the synovia is not secreted, the joints become immovable, 
etc. 
293. It is also important to observe that there is an in- 
timate sympathy between several of the secreting organs, 
especially the skin, mucous membrane of the nose, the 
intestines, the lungs, and the kidneys. If the action of 
one is interfered with, its office is assumed by another. 
Thus in cold weather, and especially if a person is not 
sufficiently protected during sleep, the pores of the skin 
become contracted and inactive, and the urinary secretion 
is increased. But the sudden contraction of these pores 
by a draft of air checks the perspiration, and determines 
either an increased action of the mucous membrane of the 
nose, when we have a cold in the head, or the extra labor 
is thrown upon the respiratory organs, and we have a cold 
upon the lungs, or the mucous membrane of the intestines 
becomes active to excess, and results in diarrhoea 
dysentery. 
When the surface of the lungs becomes diseased, or 
bronchial tubes become obstructed so that less oxygen is 
292. Illustrate the importance of the healthy action of the secreting organs. 
293. Give instances of the sympathy existing between the secreting organs. 
How should this transfer of functions be regarded ? 216 
HYGIENE. 
taken up by the lungs, the amount of carbon consumed 
in the system is too small, and an excess is therefore con- 
tained in the residuum which it is the office of the kidneys 
to remove. But with an excess of carbon this residuum 
is but slightly soluble. Hence, the urine secreted when 
there is a cold upon the lungs is highly colored, and upon 
cooling deposits a thick sediment. This insoluble sub- 
stance may be secreted so rapidly that it collects in a solid 
form in the bladder. 
This transfer of functions is a condition of disease ; but 
it is the effort of nature to relieve us from still greater 
danger. The diseased action of the lungs, nasal cavities, 
or intestines is less injurious than it would be to have in 
the system the substance which should have been excreted 
by the skin. It would, therefore, be unwise to attempt to 
check this disease directly. Allow it to continue to per- 
form, in place of the skin, a service which is necessary to 
the general health of the system, and remove the disease 
only by re-establishing that function which has been sus- 
pended. 
CHAPTER VI.—HYGIENE. 
294. Most of the principles and rules in regard to the 
preservation of health have already been stated in con- 
nection with the general subjects from which they arise, 
but it has been thought best to bring them into a more 
compact form. It may, then, be stated that the body is 
a mechanism, and, as such, must, with use, wear out. 
Such statement has been objected to on the ground of the 
perfectness of the repairing system; but it may well be 
Chapter VI.—294. Why is the body subject to wear ? Are repairs ever HYGIENE. 
doubted whether repairs are ever perfect. Certain it is 
that all severe injuries, even when cured, are in a less per- 
fect state than the same part was before the injury oc- 
curred. A wound never so heals as to leave no scar. A 
broken bone adheres completely, but rheumatism will select 
the place of fracture in preference to any other; so that 
death really begins as soon as we begin to live. Yet it is 
not improbable that the threescore years and ten might 
always be attained if no accidents were to intervene and 
if the laws of health were never violated. 
It is the business of hygiene to state, as far as they are 
known, what these laws of health are. It is not, how- 
ever, to be inferred that we should never be sick if we 
observed exactly these laws. It is probable that many 
diseases have been inherited; that is, diseases have been 
induced by infraction of hygienic laws on the part of those 
from whom we have descended, and these diseases have be- 
come so ingrafted into our systems that our natures are 
really tainted. Those singular diseases of which we can 
have but one attack, like whooping-cough, are probably the 
result of some poison fixed in the system by habits of diet 
or of life not at the time known to be hurtful. We know 
not how much of the seeds of disease we inherit, tending 
in some instances to specific disease, sometimes only to less 
perfect general constitution. 
Still this deterioration has not gone so far but that a 
proper observance of hygienic rules will dispose us to a 
healthy state, and in most cases secure us against disease. 
Our ailments are always aggravated by indiscretions, and 
in a large proportion of cases produced by them. 
perfect ? What is the object of hygiene ? Why does not the observance of 
hygienic rules invariably secure us against disease ? Can disease be inherited ? 
Are hygienic rules still useful ? How can we affect our health ? Does hygiene 
propose to cure disease ? HYGIENE. 
We can affect our health principally through the repair- 
ing system. Hence the rules of health must he based on 
the nature and use of this system. The means to be em- 
ployed may he either external or internal, but they are not 
curative means. These the physician only should use when 
disease has been induced. It is the office of hygiene to 
teach us how to use these organs so as to prevent the occur- 
rence of disease. 
295. Cleanliness.—Most of the pursuits of life soil the 
hands and even the face, and frequent washing is necessary 
as a question of decency ; but general washing of the body 
becomes necessary also as a question of health. The per- 
spiratory tubes and follicles discharge probably half of the 
excreted matter of the system. It is mostly water, but 
there is some saline ingredient and some oleaginous, both 
of which, as they do not evaporate, remain on the surface. 
Besides, the extreme outer portion of the cuticle is always 
separating in the form of minute flakes, which, however, 
continue to adhere to the cuticle. All these substances 
tend to choke up the excretory openings, and prevent them 
from effecting that relief to the system for which they were 
intended. 
It is obvious, then, that frequent, perhaps daily, ablu- 
tions are necessary. Bathing should be resorted to if pos- 
sible, but the shower-bath or washing may be substituted, 
always with the use of soap—soap and civilization are in- 
separable. After the use of water, the surface should be 
rapidly dried with a towel, and friction enough applied 
with a flesh-brush or coarse towel to establish a vigorous 
surface circulation and a general feeling of warmth and 
comfort. 
295. What Is the first law of health? Why is washing necessary? What 
should follow washing or bathing ? HYGIENE. 
219 
296. Exercise.—In a large proportion of the forms of 
human pursuit there is bodily activity enough for main- 
taining the health of the several organs. But some of 
these forms, while they are useful and even laborious, give 
exercise to only a small proportion of the organs. Thus 
the seamstress uses only the hands, the student only the 
brain, the accountant only the brain and hand. It be- 
comes necessary that some kinds of exercise be resorted to 
which have no other real object than the exercise itself. If, 
however, some other interest can be connected with it, as 
ball, boating, riding on horseback, or gymnastic feats, still 
salutary exercise is secured. Some less exciting occupa- 
tion, as walking or hand-labor, will, however, if entered 
upon with a cheerful mind, be of equal service. 
It should, however, be borne in mind by all persons who 
follow sedentary pursuits that active exercise is essential 
to the maintenance of the constitution unimpaired. Phys- 
ical activity is a necessary condition of physical health. 
Such activity induces a greater amount of respiration, 
more action of all of the muscles of the chest and abdo- 
men. The action of the heart is increased, and thus the 
circulation is augmented. With this increased respiration 
and circulation all of the powers are stimulated, digestion 
is promoted, muscular strength is increased, and mental 
activity is encouraged. The exercise should, then, be con- 
tinued till this energetic circulation is established, generally 
till sensible perspiration begins to appear. 
297. Dress.—The inferior animals are furnished, either 
by their instincts or by special variations of clothing ac- 
cording to the season, with protection against injury from 
296. What is the second condition of health ? Why is exercise beyond ordi- 
nary labor necessary ? What kind of exercise is required? What is the effect 
of exercise ? How long should it be continued ? 
297. What is the object of clothing ? Upon what does the warmth of clothing 220 
HYGIENE. 
variations of temperature. In our species this protection 
is left to our reason. The object of clothing is, in winter 
to prevent the escape of the heat which the system fur- 
nishes, and in summer to favor its escape. The warmth 
of clothing depends on the non-conducting power which 
it possesses, either from its own nature or from the stratum 
of non-conducting air which, by its porous structure, it 
imprisons. The coolness of clothing depends on the ra- 
pidity with which it conducts away the heat which the 
system furnishes. Hence woollen fabrics are the best for 
winter clothing, as they are at all seasons for persons who, 
like operatives in a rolling-mill, need to shut out the ex- 
cessive heat by which they are surrounded; and linen or 
cotton fabrics furnish the cooler varieties of clothing. 
The lighter the clothing, consistent with the requisite 
warmth, the better. 
All parts of the body require this protection, and hence 
the habit of dressing, and especially of dressing children, 
so as to expose the arms and neck is objectionable. 
The adjustment of dress is as important as the material. 
The first condition of dress is protection, but this protec- 
tion should not be at the expense of any other requisite 
of health. Especially the clothes should not be permitted 
to restrict the free action of the lungs. The compression 
of the chest is one of the extreme evils in the modes of 
female dress, and men are not wholly exempt from blame 
in this respect. Similar objection rests against the retain- 
ing of clothes of men or women in place around the waist, 
without suspending them from the shoulders; also the 
close-fitting ribbon, or necktie, or cravat around the neck; 
depend ? When is woollen clothing required ? When linen or cotton clothing f 
What amount of clothing is necessary ? What parts may be without clothing ? 
What other condition besides warmth of clothing is necessary f What injurious 
effects result from wrong methods of adjusting the clothing ? HYGIENE. 
221 
and that person will be a benefactor who can devise a 
means of keeping stockings in their place without the use 
of garters or elastics so close-fitting as to impede the cir- 
culation. 
298. Air.—The air contains about one-fifth of its volume 
of oxygen. The rest is nitrogen, except a very small pro- 
portion of carbonic acid and some watery vapor. In this 
condition it is the proper support of respiration. 
But it is liable to great deterioration. An injurious 
amount of carbonic acid is likely to accumulate by the 
process of respiration, which converts about one-fourth of 
the respired oxygen into carbonic acid. The combustion 
of gas, oil, or tallow in producing artificial light, must 
furnish a large amount of carbonic acid, enough to have a 
perceptible influence on the purity of air in the rooms 
which we occupy in the evenings. Large rooms, with high 
walls and abundant ventilation, are the only protection 
against injuries from this cause. 
Several other forms of impurity often occur. Among 
these are the dust arising from various kinds of manufac- 
ture, poison from linseed oil and paints, and especially the 
excessive accumulations of watery vapor near masses of 
water where the air is confined by the walls of cellars and 
buildings, in narrow alleys, or in deep valleys shut out from 
the action of winds. 
But the greatest danger arises from poisonous miasma, 
often in quantity too small to be detected by chemical 
tests, but in sufficient quantity to breed disease. One of 
the principal sources of this poison is decaying animal 
and vegetable matter. The remains of winter vegetables 
left in a cellar will generate it. Stagnant marshes in which 
298. What is the composition of the air ? What is the first source of dete- 
rioration mentioned ? How does the artificial light of rooms affect the air ? 
What are some of the common sources of impurity ? Wnat is the source of HYGIENE. 
the annual vegetation decays, will become covered with a 
green scum, and the whole region becomes offensive; and 
yet families will maintain a miserable existence in the im- 
mediate vicinity, with constant recurrence of chills and 
fever. Another and more poisonous miasma is generated 
in hospitals and sick-rooms. This is a necessary result of 
sickness, and is thrown off both from the surface and from 
the lungs. In many cases the poison is specific, and pro- 
duces the same diseases as those have from whom it 
emanates, as measles ; but often it has only a general de- 
pressing effect upon those who must be in attendance. 
The health must suffer, though active disease may or may 
not result. 
The general remedial agencies against these forms of 
poison must be found in the drainage of standing water, 
in removing decaying matter from the vicinity of human 
abodes, in the free use of disinfectants, such as charcoal or 
chlorine, and in sick-rooms, above everything else, abun- 
dant ventilation. Perhaps the free introduction of sun- 
light into sick-rooms will be found of value, not only as 
a disinfectant, but as a remedial agent much more effica- 
cious than has been supposed. 
299. Water may be regarded as a portion of our food, both 
because it is taken in so large quantity in the liquid state, 
and also because it forms so large a proportion of our 
solid food. It is the means of adjusting the temperature 
of the body, of eliminating the carbonic acid from the 
lungs, saline and oily substances through the skin, and the 
nitrogenized products of waste by the kidneys. 
The most important agency of water in the system de- 
pends on its great solvent power. But this property also 
greatest danger f Why are sick-rooms the source of impurity to the air ? What 
are remedial agencies ? 
299. Is water food ? What purposes does it accomplish ? Why is water so HYGIENE, 
renders it liable to be frequently contaminated. The con- 
tamination may be only slight and its effects may be only 
slowly cumulative, unobservable perhaps for months, and 
then show themselves in such forms of disease as are at 
once and obviously traceable to this source. Its work is 
imperceptibly slow, but the constitution is no less certainly 
undermined. 
The best water, that is, water containing the least for- 
eign matter, is rain-water. But water is never free from 
some foreign ingredients. Even when it has been subjected 
to natural distillation by being taken up into the atmosphere 
as vapor and condensed into clouds, and finally into rain 
and snow, it absorbs in its passage through the air oxygen, 
carbonic acid, and ammonia. These additions are not re- 
garded as hurtful. The water of springs and streams in 
granitic and other silicious geological formations, has nearly 
equal purity with rain-water. 
But the water that falls upon the surface of the earth 
where the formations are either alluvial or calcareous, re- 
appears as springs in which the water is highly charged 
with hurtful ingredients, mostly in the form of lime or 
magnesia. Waters of this kind are known in common 
language as “ hard.” Where hard water abounds, the taste 
of those who use it so adapts itself that the water is not 
disagreeable, but is greatly preferred to soft water; yet it 
is, undoubtedly, to some extent, hurtful. It compels the 
system to take on an abnormal condition, and hence favors 
either directly the occurrence of some disease, as goitre, 
or it operates conjointly with other causes in inducing 
disease of the digestive organs. 
likely to be impure ? What water is the purest ? What impurities does rain- 
water contain ? What is the character of spring-water in the regions of granite 
rocks ? Why is the water obtained from calcareous regions impure 1 What is 
this water called ? Is it wholesome ? What are the most injurious ingredients f HYGIENE. 
The so-called mineral waters, containing in solution 
saline ingredients, sulphuretted hydrogen, etc., are used 
only for their medicinal qualities, and need not here be 
considered. 
Deleterious ingredients of the more important class are 
of organic origin. Soils of every kind contain decaying 
animal and vegetable matters. Most of the springs from 
which wells are supplied must be fed from rain-water 
which has passed through such soils. The rocks through 
which it has filtered have deprived the water of much of 
its impurity, but many wells, especially those of no great 
depth, contain traces of impurities which the surface-soil 
has imparted. But no precaution can prevent impurities 
both in the wells and in the rivers in the vicinity of large 
cities, where the refuse from manufacturing establishments 
and the contents of cesspools and sewers must be disposed 
of. Hence, the obtaining of water for cities from a dis- 
tance and from the purest sources is necessary to health, 
and all requisite expenditures, however great, are regarded 
as justifiable and imperative. 
300. Food.—It must be assumed that every form of food 
is in a good condition. Thus, meats should be from healthy 
animals, and free from the taint of incipient decomposi- 
tion ; fruits should not be either unripe or over-ripe ; vege- 
tables should be fresh ; the cooking should be to that ex- 
tent most conducive to digestion ; butter should be free 
from rancidity ; bread should be porous, sweet, well baked, 
and not entirely new, etc. 
As the object of food is to provide for the growth and 
supply the waste of the system, both the amount and kind 
Why is well-water likely to he impure ? Why cannot the water of wells and 
rivers near large cities be pure ? How is the evil to be remedied ? 
300. What are the requisites of good food, as meats, fruits, etc. ? What 
amount of food is necessary before growth is completed ? How should the amount HYGIENE. 
225 
should be such as to meet these wants. Hence the amount, 
before full growth is attained, should exceed the waste. 
After growth is complete, the amount should vary with the 
occupation, increasing with the increase of our activities, 
in order to the continued production of force ; increasing 
also with the exposure to low temperatures, in order to 
supplement the reduced amount of external heat by a larger 
supply of vital heat. 
The kind of food should also vary with our condition. 
Mtrogenized food, and considerable of it in the form of 
animal food, is required when much force is to be expended. 
Respiratory food is required in cold weather; and in high 
latitudes or where there is great exposure, it should be in 
large quantity and in the most concentrated form, that is, 
in the form of animal fats. In a mild or warm tempera- 
ture, where little effort is called for, a vegetable diet will 
best meet the wants of the system. 
Any kind of food long persisted in, however suitable it 
may be in all other respects, is unfavorable to health. 
There must he change, diversity. 
Generally correct ideas about food being established, it 
ought to be added that nothing is more certain to induce 
disease than the constant apprehension that our food may 
injure us. Special solicitude about the effects of food upon 
us will soon induce hypochondriasm, which is itself disease 
and the forerunner of many diseases. 
Insufficiency of food is a prolific source of disease. Even 
though the scantiness do not approach starvation, or pro- 
duce the sufferings of real hunger, if the supply fall below 
the actual waste, the powers become enfeebled, the mind 
be adjusted afterward ? How should the nitrogenized food he regulated ? How 
the respiratory food ? Can a uniform diet be safely adopted ? Should we be con- 
stantly anxious about the effects of our food ? What effects follow from insuffi- 
ciency of food 1 What from excess of food ? GENERAL QUESTIONS. 
loses vigor, energy is weakened, the ambition of success 
subsides, the physical strength fails, and low febrile symp- 
toms, and finally some form of typhoid disease generally 
follows. If the deficiency is in the vegetable ingredient-4 
of food, scurvy is apt to follow. If it be in the oleaginous 
portion, a scrofulous habit supervenes, and finally tubercu- 
lar consumption. 
Excess of food is equally injurious. When more is taken 
into the system than can be appropriated for its purposes, 
either the stomach is overtaxed and dyspepsia results, or 
the liver is overtaxed and bilious fevers are induced. 
Give the analysis of the repairing system. 
GENERAL QUESTIONS ON THE REPAIRING SYSTEM. 
Chapter I.—Describe the peritoneum. Of what do the sections of this chap- 
ter, in their order, treat ? 
Section I.—Describe the mode of development of the teeth. How are they 
divided f In the case of the teeth, w'hat are the three precautions to be observed ? 
Describe the salivary glands. The tongue. The pharynx. The esophagus. The 
physiology of mastication and deglutition. 
Section II.—Describe the stomach. Give the physiology of the stomach. 
Why does the digestive system require special care ? What are the two objects 
for which food is taken ? What circumstances require the most concentrated, 
and what the least concentrated food ? What are the general principles for the 
selection of food in health ? What in dyspeptic disease ? Why are liquid sub- 
stances required in the system ? How are they received into the circulation ? 
What modifications in food are effected by cooking, and how do these changes 
affect the system ? How are wfe to judge of the quantity of food needed 1 What 
are the practical rules in reference to the times of taking food, and what are the 
grounds of them ? What are the conditions favorable to digestion ? 
Section III.—Describe the duodenum. The liver. The pancreas. Give the 
physiology of these organs. 
Section TV.—Describe the small intestine. The mesentery. Give the physi- 
ology of the small intestine. Describe the large intestine. 
Chapter II.—Describe the blood. The pericardium. The heart. Its valves. 
The arteries. Their valves. The distribution of the arteries. The veins. The 
course of the circulation. The forces by which it is sustained. The amount of 
daily circulation. How is the pulse produced ? What rules are to be observed 
when an artery is wounded ? For what purpose is the anastomosing of the ar- GENERAL QUESTIONS. 
teries ? How may we estimate the amount of nutrition performed ? Where does 
nutrition take place ? Describe the capillaries and their use. 
Chapter III.—Describe the pleura. The larynx. How is the voice produced ? 
Describe the trachea. The lungs. How is respiration produced ? What is the 
ordinary amount of respiration ? What circumstances affect the amount ? What 
proportion is oxygen ? What circumstances may vary the amount of oxygen re- 
ceived ? From what sources is carbonic acid derived ? How is it injurious ? 
Why should rooms intended for a large number of persons be well ventilated ? 
How is the oxygen received into the blood ? How much is received in compari- 
son with the amount of blood circulated ? What changes are effected in the 
blood by respiration ? In what way are these changes made ? What is the vital 
force ? How does it become mechanical force ? Give the facts which corrobo- 
rate this explanation. What is the second object of respiration ? How is the 
heat produced ? WThat are the two kinds of food ? What is the composition of 
each? Give examples of each. What is the object of each in the system ? Un- 
der what circumstances should each kind be used ? 
Chapter IV.—For what are the lacteals designed ? How is it shown that the 
veins act as absorbents ? Describe the third class of absorbents. Their office. 
What conditions of the system depend upon their activity ? 
Chapter V.—What are the four classes of secretions ? Describe the secreting 
process. What are the organs of secretion ? What secretions are performed by 
surfaces ? Describe the follicles and their physiology. The perspiratory appa- 
ratus. What is its physiology as an excretory system, as connected with the 
temperature of the body ? What are the principal glands ? Describe the kid- 
neys and their use. The spleen and thymus and thyroid glands. The relation 
existing between the secreting organs. APPENDIX. 
The following description of the individual muscles has 
been, without changing the paging or the numbers of the 
paragraphs, transferred to this position in the book instead 
of following the section on the muscles generally, because, 
while it is too technical to be required of classes in recita- 
tion, it is believed that many will feel sufficient interest in 
the subject to give it ex- 
amination. 
Fig. 56. 
SECTION II.—The 
Muscles individually. 
80. I.—Muscles of the 
forehead. 
(a) The occipito- 
frontalis (k, I, Fig. 56) 
arises from the ridge of 
the occipital bone, ex- 
tends forward so as to 
cover the top of the cra- 
nium, and is inserted into 
the skin at the lower part 
of the forehead. It raises 
the eyebrows and wrin- 
kles the forehead hori- 
zontally. 
Muscles of the Face, a The levator lahii su- 
perioris. b The levator anguli oris, c The 
depressor anguli oris, d The depressor 
lahii inferioris. e The zygomaticus major. 
g The buccinator, h The orbicularis oris. 
i The levator alse nasi, i The compressor 
naris. k I The occipito-frontalis. m The 
orbicularis oculi. q The masseter muscle. 
(d) The corrugator 
supercilii (not represented in the figure) arises from the 230 
APPENDIX. 
frontal bone near the inner angle of the eye, runs upward 
and outward, and is inserted into the skin under the eye- 
brow. It antagonizes with the frontalis, and wrinkles the 
forehead vertically. 
81. II.—Muscles of the eye. 
(a) The straight muscles, namely, the rectus superior 
(9, Fig. 57), the rectus 
inferior (13), the rectus 
internus (10), and the 
rectus externus (11, 
13, most of it is repre- 
Fig. 57. 
sented as removed in or- 
der to show other parts). 
These four muscles arise 
in the posterior part of 
the orbit, and extend for- 
ward to be inserted into 
the eyeball, one above, one 
below, and one on each 
side. Acting separately, 
Muecles of the Eye. 2 The optic nerve. 3 
The eyerball. 4 The levator muscle of the 
eyelid. 5 The superior oblique muscle. 
6 The loop through which its tendon 
passes. 7 The tendon which is inserted 
into the ball. 8 The inferior oblique 
muscle. 9 The rectus superior. 10 The 
rectus internus. 11, 12 Portions of the 
rectus externus. 13 The rectus inferior. 
they roll the eye in different directions; acting together, 
they depress the ball in the socket. 
(b) The oblique muscles. The obliquus superior (5) 
has a common origin with the recti muscles. It runs 
obliquely over the eye to the inner angle, where its tendon 
passes through a cartilaginous ring (6), and is reflected 
back to he inserted into the ball (near 3). The obliquus 
inferior (8) arises near the inner angle of the eye, runs 
obliquely backward under the eye, and is inserted into the 
posterior part of the ball. The oblique muscles, acting 
separately, roll the eye in opposite directions; acting to- 
gether, they antagonize with the recti muscles, and bring 
the ball forward. 
(c) The levator palpebrse superioris (4) has a APPENDIX. 
231 
common origin with the recti muscles, and is inserted into 
the cartilage which forms the upper eyelid. 
(d) The orbicularis oculi {m, Fig. 56) is a circular 
muscle surrounding the eye. It has its origin and inser- 
tion common at the inner angle, and its use is to close the 
eye. 
82. III.—Muscles of the nose. 
{a) The compressor naris {j, Fig. 56) arises from the 
corner of the nose, spreads over the ridge of the nose, and 
its fibres mingle with those of the corresponding muscle 
from the other side. Its action is to diminish the size of 
the nostrils. 
(b) The levator alse nasi (i, Fig. 56) arises from the 
nasal process of the superior maxillary bone, and is inserted 
into the corner of the nose. It enlarges the nostrils. 
83. IV. Muscles of the mouth. 
{a) The levator labii superioris («) has its origin 
directly below the eye, and is inserted into the middle of 
the upper lip. It raises the lip. 
(b) The depressor labii superioris is a short muscle 
within the mouth which arises near the root of the upper 
canine tooth, and is inserted into the upper lip just below 
the nose. 
(c) The levator anguli oris (b) arises just below the 
eye, and is inserted into the corner of the mouth, which 
it is designed to raise. 
(d) The depressor anguli oris (c) arises from the 
lower edge of the lower jaw bone, and is inserted into the 
corner of the mouth, which it depresses. 
(e) The levator labii inferioris arises near the roots 
of the lower incisor teeth, passes downward, and is inserted 
into the integuments of the chin. It raises the lower 
lip. 
(/) The depressor labii inferioris {d) arises from 232 
APPENDIX. 
the lower edge of the lower jaw on the side of the chin, 
and is inserted into the lower lip, which it depresses. 
(g) The buccinator (g) arises from several points near 
the joint of the lower jaw, constitutes the principal part 
of the cheek, and comes forward to be inserted into the 
corner of the mouth. It diminishes the cavity of the 
mouth, or draws back the angle of the mouth. 
(/i) The orbicularis oris (/i) is a broad, circular mus- 
cle encompassing the mouth. It antagonizes with all the 
muscles that tend to open it. 
84. Y.—Muscles which move the lower jaw. 
(a) The temporal muscle (4, Fig. 9) arises from the 
parietal bone, and the fasciculi converge till it becomes 
tendonous and passes under the zygomatic process, and is 
inserted into the coronoid process (5). It raises the lower 
jaw. 
(h) The masseter muscle (q, Fig. 56) arises from the 
malar portion of the zygomatic process, from the malar 
bone, and from the contiguous portion of the upper max- 
illary. One portion has its fibres so situated, that, being 
inserted into the root of the 
coronoid process, by contrac- 
tion it carries the lower jaw 
backward. The other and 
principal portion is inserted 
into the angle of the jaw. It 
tends slightly to bring the jaw 
forward, but its principal use 
is to assist the temporal muscle 
in mastication. 
Fig. 58. 
(c) The pterygoid muscles 
(of which 1, 2, Fig. 58, is the 
exterior and 3 is the interior) 
arise from each pterygoid pro- 
The two Pterygoid Muscles. Parts 
of the upper and lower jaws are 
removed to exhibit them. 1, 2 
The external and 3 the internal 
pterygoid muscles. APPENDIX. 
233 
cess, and are inserted into the inner surface of the angle 
of the jaw. They act alternately, and therefore produce 
the horizontal, grinding motion of the jaw. 
85. VI.—Muscles of the throat. 
(a) The sterno-hyoideus {I, Fig. 59) arises from the 
top of the sternum, and is inserted into the os hyoides. It 
Fig. 59. 
Muscles of the Neck. 
draws the hyoides downward and forward. 
(b) The omo-hyoideus {m m) arises from the upper 
edge of the scapula near the outer angle, and is inserted 
into the os hyoides. It draws the hyoides downward and 
backward. 
(c) The mylo-hyoideus arises from the lower edge 
of the lower maxillary hone, and is inserted into the os 
hyoides. It forms the floor of the mouth, and the body 234 
APPENDIX. 
of the tongue rests upon it. It brings the hyoides upward 
and forward. 
(d) The stylo-hyoideus (9) arises from the styloid 
process, and is inserted into the os hyoides. It draws the 
hyoides upward and backward. 
(e) The digastricus {p p) arises from the mastoid 
process, passes downward and forward through a perfora- 
tion in the stylo-hyoideus to the os hyoides, to which it is 
attached, then changing its direction, it goes to be inserted 
into the point of the chin. It lifts the os hyoides, and with 
it the tongue and throat. But when the sterno-hyoideus 
and the omo-hyoideus are in a state of contraction so that 
the hyoid bone cannot rise, then the mylo-hyoideus and 
the digastricus will draw the lower jaw downward. 
86. VII.—Muscles of the neck. 
(a) The sterno-cleido-mastoideus (the prominent 
oblique muscle on each side of the neck) arises from the 
sternum and clavicle, goes obliquely upward and back- 
ward, and is inserted into the mastoid process. When one 
muscle alone acts it brings the head obliquely forward. 
When they act on both sides at the same time, the head 
is brought directly forward. 
(h) The splenius arises from the spinous and trans- 
verse processes of the vertebral column as far down as the 
fifth dorsal vertebra, and, as it ascends along the back, 
goes obliquely to be inserted just back of the mastoid pro- 
cess. (2, pi. I.) 
(c) The coxnplexus has nearly the same origin and 
course, but has its insertion into the occipital bone directly 
behind the insertion of the splenius. (1, pi. I.) When 
the splenius and complexus act on both sides they move 
the head directly backward. When only those on one side 
act they turn the head obliquely backward. These two 
muscles are the antagonists of the mastoideus. When all APPENDIX. 
235 
these muscles act together by a moderate force, they tend 
to keep the head in an erect position. 
(d) The obliquus capitis inferior arises from the 
spinous process of the second cervical vertebra, and is in- 
serted into the transverse process of the first. It, there- 
fore, turns the first vertebra horizontally on the pivot joint, 
between it and the second, and the head partakes of the 
csame horizontal motion. If, however, both muscles act 
together, they tend to steady the head in its position. 
87. YIII. — Muscles which 
move the spine. 
(a) The longissimus dorsi 
{d e, Fig. 60) arises from the 
spinous processes of the sac- 
rum and the lumbar vertebrae, 
and from the contiguous por- 
tions of the ilium, passes up 
along the spine, filling the 
space between the spinous and 
transverse processes, and is in- 
serted into the transverse pro- 
cesses of all the dorsal vertebrae 
except the lowest. Its use is to 
keep the spine erect. It also 
helps to bend it backward, or 
obliquely backward. 
Fig. 60. 
{b) The sacro lumbalis 
{a b) has nearly the same origin 
as the longissimus, and is in- 
serted into the ribs a little for- 
ward of each tubercle. Its use 
is the same as that of the 
longissimus. 
, \ ml , , i 
(c) The quadratus lum- 
d e The loiwiPBimus dorsd. a b The 
eacro lumbalis. c o The levatores 
costamm. APPENDIX. 
borum arises from the highest portions of the rim of the 
pelvis, and is inserted into the transverse process of the 
last dorsal vertebra, and into the lower edge of the lowest 
rib. It keeps the trunk erect, or bends it to either side. 
88. IX.—Muscles of respiration. 
(a) The serratus posticus superior arises from the 
spinous processes of the three lower cervical vertebrae, and 
is inserted into the second, 
third, and fourth ribs on the 
front side of the thorax. Its 
direct use is to raise these 
ribs, but from the manner in 
■which the ribs are connected 
it tends to raise all of the 
ribs. 
(b) The levatores costa- 
rum (c o, Fig. 60), twelve in 
number, arise one from the 
transverse process of the last 
cervical and each of the dor- 
sal vertebrae except the last, 
and passing obliquely down- 
ward is inserted into the rib 
immediately below. They as- 
sist the serratus posticus su- 
perior. 
Fig. 61. 
(c) The intercostales (4 
and 5, Fig. 61) are short mus- 
cles filling the spaces between 
the ribs. The internal layer 
passes upward and forward. The external layer runs 
obliquely upward and backward. When the upper rib 
becomes fixed by the action of the muscles above it, the 
intercostales raise all the ribs below the first. 
4 External intercostal muscles. 5 In- 
ternal intercostal muscles. 6 The 
transversalis muscle. 8 The linea 
alba. 11 The rectus abdominis. APPENDIX. 
(d) The serratus posticus inferior (16, Fig. 62) 
arises from the spinous processes of the lumbar vertebras, 
and rising forward, are inserted into the ends of the tenth, 
eleventh, and twelfth ribs. It brings the ribs downward. 
Fig. 62. 
1 The trapezius. 4 The latissimus dorsi. 5 The deltoid muscle. 8 The glutens 
medins. 9 The gluteus maximus, 11, 12 The rhomboideus muscle. 16 The 
serratus posticus inferior. 22 The serratus anticus major. 
(e) The diaphragm (2, 2, Fig. 63) is a muscular mem- 
brane separating the cavity of the thorax from that of the APPENDIX. 
abdomen. Its form is that of a dome, being convex 
above, like an inverted basin. It is seen in section in 
Fig. 63. It is attached to the lower extremity of the ster- 
num and to the ends of all the ribs. Its muscular fibres 
Fig. 63. 
have a very irregular arrangement, but the general effect 
of their contraction is to depress the dome more nearly to 
a plain surface, and of course to increase the cavity of the 
thorax by pressing down the viscera of the abdomen. 
The Thorax, the front part removed to show the diaphragm, 2, 2. 
89. X.—Muscles of the abdomen. APPENDIX. 
(«) The obliquus descendens externus (12,13, Fig. 
64) arises from the extremities of the eight inferior ribs, 
and proceeds obliquely downward to the linea alba 
Tig. 64. 
Front view of the Muscles of the Trunk. 1 The pectoralis major. 2 The deltoid 
muscle. 12, 13 The external oblique muscle. 16 The rectus abdominis. 18 
The internal oblique muscle. 
(which is a tendonons substance occupying the median 
line of the abdomen, from the sternum to the pelvis, and 
seen at 8, 9, Fig. 61). 
{h) The obliquus ascendens internus (18, Fig. 64) 
arises from the brim of the pelvis, and is inserted into the 
linea alba, sternum, and false ribs. 
(c) The transversalis abdominis (6, 7, Fig. 61) 240 
APPENDIX. 
arises from the lumbar vertebrae and the ends of the false 
ribs, and passes horizontally around the abdomen to be 
inserted into the linea aspera. 
(d) The rectus abdominis (16, Tig. 64) arises from 
the sternum and the cartilages immediately adjacent, and 
descends vertically to the pelvis. 
The direct use of these muscles is to compress the abdo- 
men. But by so doing they cause the viscera of the abdo- 
men to ascend, and the arch of the diaphragm is raised 
up. As the diaphragm descends, these muscles relax to 
make room for the depressed viscera.48 They are thus the 
muscles which antagonize with the diaphragm, and though 
they have other uses, they are also respiratory muscles. 
The first, second, and fourth also bend the body obliquely 
or directly forward. 
90. XL—Muscles of the upper extremities. 
(a) The trapezius (1, Fig. 62) arises from the occipital 
bone, from a tendonous substance called the ligamentum 
nuchas, which passes along the spinous processes of the 
neck, and from the spinous processes of all the dorsal ver- 
tebrae. It is inserted into the spine of the scapula and 
into the acromion process. It draws the scapula backward. 
1. Muscles of the Scapula. 
48 It is in this way that exercise is essentially connected with digestion, 
and that a want of exercise brings on a constipated state of the intestines. 
Exercise always increases the demand for oxygen in the system; hence 
the deep, labored respiration of a person who has been exerting himself to 
his utmost. To a less extent, and yet to a very perceptible extent, ordi- 
nary and not fatiguing exercise increases the fullness of the respiratory 
effort; that is, it increases the reciprocal action of the abdominal muscles 
and the diaphragm. There is thus an increased motion mechanically given 
to the stomach and intestines. The effect of this is to increase the supply 
of blood sent to these organs, and thus to favor digestion and prevent 
dyspepsia. Another effect is to keep their contents in motion, and thus to 
prevent constipation. APPENDIX. 
241 
(b) The rhoxnboideus (11, 13, Fig. 63) arises from the 
spinous processes of the three lower cervical and the four 
upper dorsal vertebrae, and is inserted into the whole pos- 
terior edge of the scapula. It draws the scapula upward 
and backward. 
(c) The serratus anticus major (22, Fig. 62) arises 
along the sides of the thorax from the eight superior ribs, 
runs back under the scapula and is inserted into the pos- 
terior edge of it. It moves the scapula downward atd 
forward. 
3. Muscles which move the shoulder-joint. 
(a) The pectoralis major (1, Fig. 64) arises from the 
whole length of the sternum and the fibres converging. 
It is inserted into the fore side of the humerus, about 
three inches from its upper extremity. It brings the arm 
downward and forward. 
(b) The latissimus dorsi (4, Fig. 63) arises from the- 
spinous processes of the lumbar vertebrae and sacrum, and 
from the edge of the ilium, and is inserted into the hu- 
merus just back of the insertion of the pectoral muscles. 
It draws the arm downward and backward. 
(c) The deltoides (5, Fig. 63) arises from the spine 
of the scapula, the acromion, and the outer extremity of 
the clavicle, passes over the shoulder-joint, and is inserted 
into the outer side of the humerus near the middle. It 
raises the arm. 
{a) The biceps flexor cubit! (8, pi. II.) arises from 
the upper edge of the glenoid cavity and from the coracoid 
process of the scapula, and, passing the whole length of 
the humerus, it is inserted into the tuberosity at the upper 
end of the radius. It bends the forearm. 
3. Muscles which move the elbow-joint. 
(b) The brachialis interims, situated under the 
biceps, arises from the humerus, near the insertion of the 242 
APPENDIX. 
deltoid muscle, and is inserted near the upper extremity 
of the ulna, on the front side. Its use is the same as the 
previous muscle. 
(c) The triceps extensor cubiti (7, pi. I.) arises from 
the lower edge of the glenoid cavity, from the upper ex- 
tremity and from the middle of the humerus, and is in- 
serted into the olecranon. It extends the forearm. 
The muscles of this division have three objects, to rotate 
the hand, to move the wrist, and to move the. fingers. 
Seven of these arise from the internal condyle, of which 
the first is a pronator and the rest are flexors. 
4. Muscles which move the wrist and fingers. 
{a) The pronator teres radii (7, pi. II.) passes 
obliquely over the forearm, and is inserted near the middle 
of the radius. It rolls the hand inward. 
(b) The flexor carpi radialis (9, pi. II.) follows down 
near the radius, passes under the annular ligament, and 
is attached to the metacarpal bone of the forefinger. It 
bends the wrist. 
(c) The flexor carpi ulnaris takes its course along 
the ulna, and is inserted into the pea-shaped bone of the 
wrist. It bends the wrist. 
(<7) The palmaris longus has nearly the same course 
as the preceding muscle, and is inserted into the mem- 
branous expansion which lies in the palm of the hand, 
and has also a slender attachment to the bones of the hand. 
It helps to bend the wrist. 
(e) The flexor digitorum sublimis (10, pi. II.) passes 
as one muscle to the middle of the forearm, when it divides 
into four parts, which soon become tendonous, pass under 
the annular ligament, and are inserted one into the second 
phalangeal bone of each finger. -It bends the fingers at the 
first and second joints. 
(/) The flexor digitorum profundus lies under the APPENDIX. 
243 
sublimis, is also divided into four tendons, and they are 
inserted into the last bone of each finger. It therefore 
bends the last joint. 
(g) The flexor longus pollicis is inserted into the 
last bone of the thumb. It bends all the joints of the 
thumb. 
The next six muscles arise from the external condyle 
of the humerus, of which the first is a supinator, and the 
rest are extensors. 
(a) The supinator radii longus (8, pi. I.) passes 
obliquely over and nearly around the forearm, and is in- 
serted into the lower end of the radius. It rolls the hand 
outward. 
(b) The extensor carpi radialis descends along the 
back of the radius, and is inserted into the metacarpal 
bone of the forefinger on the back of the hand. It ex- 
tends the hand. 
(c) The extensor carpi radialis brevior resembles 
the last, except that it is inserted into the metacarpal bone 
of the second finger. It extends the hand. 
(d) The extensor carpi ulnaris descends along the 
ulna, and is inserted into the metacarpal bone of the little 
finger. It extends the hand. 
(e) The extensor digitorum communis (9, pi. I.). 
At the middle of the forearm it divides into three tendons, 
which are inserted into the middle bones of the first, sec- 
ond, and third fingers. A strip of tendon also reaches to 
the last bones of the same fingers. It extends all the joints 
of these fingers. 
(/) The extensor minimi digiti is inserted in a 
similar manner into the bones of the little finger, and ex- 
tends all the joints. 
(g) The extensores pollicis arise from the middle 
of the ulna, and are inserted, one into the metacarpal bone 244 
APPENDIX. 
of the thnmb, and one into each of the other bones of 
the thumb, and extends all the joints. 
91. XII.—Muscles of the lower extremities. 
1. Muscles which move the thigh, 
Fig. 65. 
(a) The psoas magnus 
{a, Fig. 65) arises from the 
front side of the bodies and 
transverse processes of the 
lumbar vertebrae, runs across 
the pelvis to the os pubis, 
bends over the anterior edge 
of this bone, and is inserted 
into the trochanter minor of 
the femur. It brings the 
thigh forward. 
(£) The iliacus inter- 
ims {i, Fig, 65) arises from 
the whole internal surface of 
the wing of the ilium. Its 
fibres converge, become ten- 
donous, and unite with the 
tendon of the psoas magnus. 
Its action is, therefore, the 
same as the psoas. 
(c) The gluteus maxi- 
mus (13, pi. I.) arises from 
the external surface of the 
sacrum and coccyx and the 
lower external surface of the 
ilium, and is inserted into 
the upper part of the linea 
aspera for a third of the 
length of the thigh. Its use 
a The psoas matrons muscle. b The ili- 
acus interims, c One of the intercos- 
tal muscles, d Part of the femur. 
e, e The bones of the pelvis. 
is to straighten the thigh and draw it backward. But as APPENDIX. 
245 
important an office is, in connection with other muscles, 
to support the body in an erect position on the lower ex- 
tremities. 
{d) The gluteus xnedius (13, pi. I.) arises from the 
outer surface of the spine of the ilium, and is inserted into 
the back part of the trochanter major. It carries the thigh 
outward, and also turns the toes outward. 
(e) The gluteus minimus arises from that part of the 
ilium contiguous to the acetabulum, and is inserted into 
the front side of the trochanter major. The effect of this 
muscle is to turn the thigh so as to carry the toes in- 
ward. 
(/) The triceps adductor arises from the upper and 
front part of the os pubis, by three heads, and is inserted 
into the whole length of the linea aspera. It rotates the 
thigh, and brings it inward. 
(g) The obturator externus arises from the large 
foramen in the os ischium, passes under the neck of the 
femur, and is inserted into the inner and back part of the 
trochanter major. It rotates the thigh outward. 
2. Muscles which move the leg. 
{a) The sartorius (11, pi. II.) arises from the upper 
and front part of the ilium, winds obliquely to the inside 
of the leg, and is inserted into the inner tubercle of the 
tibia. It bends the leg, and draws it obliquely inward. 
The next four muscles lie on the under side of the thigh, 
£nd their office is to bend the knee. 
{b) The gracilis (14, pi. I.) arises from the os pubis 
near its inferior part. 
(c) The semi-tendinosus (17, pi. I.) arises from the 
lower extremity of the ischium. 
lower extremity of the ischium. These three muscles, to- 
gether with the sartorius, have a common insertion at the 
(d) The semi-membranosus also arises from the 246 
APPENDIX. 
inner tubercle of the tibia, by a common tendon which 
forms the inner hamstring. 
(e) The biceps cruris (16, pi. I.) arises from the lower 
extremity of the ischium, and from the linea aspera near 
the insertion of the gluteus maximus, and is inserted into 
the outer tubercle of the tibia. Its tendon constitutes the 
outer hamstring. 
The remaining four muscles constitute the extensor of 
the leg. 
(/) The rectus femoris (13, pi. II.) arises from the 
front part of the ilium. 
{g) The crureus arises from the trochanter 
minor. 
(h) The vastus internus (13, pi. II.) also arises from 
the trochanter minor. 
(t) The vastus externus (14, pL II.) arises from the 
trochanter major. 
These four muscles unite in one great tendon, which is 
inserted into the patella. A short tendon connects the 
patella with the tibia where the power is to be exerted. 
3. Muscles which move the foot. 
(«) The gastrocnemius (19, pi. I.) arises from both 
condyles of the femur. 
(/;) The soleus arises from the tubercles of the tibia. 
These muscles unite in a strong tendon (the tendon 
Achillis, 21, pi. I.) which is inserted into the extremity of 
the heel (the os calcis). (The tendon is seen above, 3, 
Tig. 42.) They extend the foot. 
(c) The peroneus (20, pi. I.) arises from the head of 
the fibula. It follows this bone to its lower extremity, 
passes through the channel of the outer ankle, turns under 
the foot, and is inserted into the metatarsal bone of the 
great toe. It extends the foot, and presents the sole 
obliquely outward. APPENDIX. 
247 
(d) The tibialis posticus arises from the upper ex- 
tremity of the tibia, passes down on the back side between 
the tibia and fibula, turns under the foot just back of the 
malleolus internus, and is inserted into the middle of the 
under side of the foot. It extends the foot slightly, and 
presents the sole obliquely inward. 
(e) The tibialis anticus (19, pi. II.) arises from the 
head of the tibia on the front side, passes down forward 
of the malleolus internus, and is inserted with the posticus. 
It flexes the ankle slightly, and turns the sole inward. 
4. Muscles which move the toes. 
(a) The flexor pollicis pedis arises a little below the 
head of the fibula on the back side, passes behind the ankle- 
joint on the inside to the bottom of the foot, and is in- 
serted into the under side of the last bone of the great toe. 
It bends this toe. 
(b) The flexor digitorum pedis resembles the flexor 
pollicis pedis till it reaches the bottom of the foot, where 
it divides into four tendons, which are inserted one into 
the last bone of each toe except the first. It bends these 
toes. 
(c) The extensor pollicis pedis (16, pi. II.) arises 
from the front side of the head of the fibula, passes along 
the bone to the ankle, then under the annular ligament, 
and is inserted into the upper side of the last bone of the 
great toe. It extends the great toe, and bends the ankle. 
(<d) The extensor digitomm pedis (17, pi. II.) is 
like the pollicis pedis till after it passes under the annular 
ligament, where it divides into four tendons, which are in- 
serted one into the top of the last bone of each toe except 
the first. It extends the toes and bends the ankle. INDEX AND GLOSSARY. 
THE NUMBERS REFER TO THE PARAGRAPHS. 
Abdomen, 182. 
Abciuc'tor oc'uli. (L. dbduco, to lead 
away.) The nerve which goes to the 
external straight muscle ot the eye. 
Absorption, 274. 
of nutriment, 199. 
Acro'mion. (Gr. axpoi, the highest 
part, and go jug's, the shoulder.) The 
prominent part of the shoulder. 44. 
Acetab'ulum, 43. 
Adaptation in the nerves of general sen- 
sibility, 122. 
Adaptation of the eye to different dis- 
tances, 133. 
Ad'ipose, fat. 
Air, 298. 
Albu'men, a nutritious substance which 
hardens by heat, of which the white of 
an egg is an example. 
Al'cohol, 206. 
Amount of the circulation. 245. 
“ “ respiration, 259. 
“ “ sleep, 171. 
Anas'tomose. (Gr. ava, through, and 
Sto/ucc, a mouth.) The opening of 
arteries and veins into larger ones, 
218. 
Anatomy, object of, 1. 
Anfrac'tuosities, 87. 
Animal heat, 270. 
Animal and vegetable food. 203. 
Antag'onism of the muscles, 73. 
An'trum maxillare. (L. antrum, a cave.) 
A cavity in the upper jaw. 24. 
Aor'ta, 241. 
Aqueous humor, 127. 
Arach'noid membrane. (Gr. apaxvrf, 
a spider, resembling a spider’s web.) 
83. 
Ar'bor vitae. (L. Tree of life.) 89. 
Articulation. (A joint.) 
Arrangement of muscles, 71. 
Ar'tenes, 238. 
Aryte'noid. (Gr. apwaiVOt, a ewer, 
ewer-shaped.) 254. 
Astrag'alus, 51. 
Atlas, a3. 
Au'ditory nerve, 142. 
Au'ricle,' 236. 
Ax'illary. (L. axilla, the arm-pit.) 
Ax'is, 33. 
Ball and socket joints, 65. 
Bathing, 288. 
Belly of the muscles, 68. 
Bile, 216. 
Blood, 231. 
Blood-cells, 233. 
Bones of the cranium, 11,12. 
“ “ ear, 140. 
“ “ face, 22. 
“ “ foot, 54. 
“ “ forearm, 47. 
“ “ hand, 48. 
“ “ head, 11, 12. 
“ “ lower extremities, 50 
“ “ pelvis, 41. 
“ “ spine, 31. 
“ “ thorax, 38. 
“ “ upper extremities, 46, 
Brain, its agency in mental operations, 
95. 
Brain, as a means of manifesting voli- 
tion, 94. 
Brain, an organ of the mind, 92. 
“ a repository of force, 91. 
“ dependence on the blood, 101. 
“ “ “ emotions, 103. 
“ excessive activity, 102. 
“ gray substance of, 89. 
“ overworking, 100. 
“ training, 99. 
“ white substance, 89. 
Bron'chi, the divisions of the trachea, 
255. 
Ca'nine. (L. cants, a dog.) The name 
of the third tooth, 186. 
Capillary systems. (L. capillus, a hair.) 
251. 
Capsule. (L. capsula, a casket.) The 
membrane which incloses the cavity 
of a joint. 58. 
Carbon'ic acid in the air, 262. 250 
INDEX AND GLOSSARY. 
Car'diac. (L. cardiacus, pertaining to 
the heart.) The orifice of the stomach 
on the left. 196. 
Came®. (L. earn, flesh.) Fleshy. 
Carniv'orous, living on flesh. 
Carotid artery, 241. 
Car'pal. (L.'carpus, the wrist.) Per- 
taining to the wrist. 
Car'tilages of the joints, 57. 
Cause of deafness, 148. 
Cel'lular membrane. Note 20. 
Cerebel'lum, the lower and back part of 
the brain, 85. 
Ce'rebrum, the upper and front part of 
the brain, 85. 
Cer'vical. (L. cervix, the neck.) Per- 
taining to the neck. 
Changes effected by respiration, 265. 
Choice of food, 204. 
Cho'roid. (Gr. x°f}iov.) The second 
coat of the eye. 126. 
Chyle* 222. 
Chyme, 198. 
Cil'iary. (L. cilium, the eye-lash.) Con- 
sisting of filaments. 127. 
Circulation, 231. 
Cleanliness. 295. 
Clavicle. (L. clavis, a key.) 45. 
Coag'ulum, the clot of blood, 247. 
Coc'cyx, the lowest bone of the spine, 
81. 
Coch'lea. (L. a snail-shell.) Part of the 
labyrinth. 141. 
Cochlea, its functions, 146. 
Combined action of muscles, 
Composition of bones, 7. 
Conditions of digestion, 212. 
Conductors of sound, 144. 
Con'dyle. (Gr. xovdvXoi, a button.) 
A protuberance. 
Condyloid joints, 64. 
Conjuncti'va. (L.) The transparent 
membrane which covers the front part 
of the eye. 125. 
Contents of the lymphatic vessels, 278. 
Convolutions of the brain, 87. 
Cooking of food, 207. 
Cornea. (L. cornu, horn.) The trans- 
parent coat of the eye' under the con- 
junctiva, 126. 
Coracoid. (Gr. xopaq, a crow, resem- 
bling a crow’s bill.) Applied as the 
name of several processes. 
Coronal. (L. corona, a crown.) Suture. 
20. 
Coronoid processes, 47. 
Cor'pus callo'sum. (L. a hard body.) 
The fibrous mass between the hemi- 
spheres of the brain, 88. . v 
Course of the blood, 243. 
Cra'nial nerves, 111. 
Cranium, form of the, 19. 
“ uses of the, 21. 
Cri'coid. (Gr. KpiHOi, a ring.) Car- 
tilage. 254. 
Crystalline lens, 127. 
Cutaneous secretion, 285. 
absorption, 280. 
Cuticle. (L. cutis, skin.) 163. 
Deglutition, the act of swallowing, 194. 
Deuta'tus. (L. dens, a tooth.) A tooth- 
like process. 33. 
Development of bones, 6. 
Digestion, 181. 
Diet, rules of, 200. 
Dip'loe. (Gr. 6ntXovi, double.) 12. 
Direction of visible objects, 128. 
Distribution of nerves, 115. 
Diversity of food, 201. 
Dorsal. (L. dorsum, the back.) Per- 
taining to the back. 
Double circulation, 249. 
Dreaming, ITS, 
Dress, 297. 
Duode'num. (L. twelve.) The com- 
mencement of the small intestine. 215. 
Dura mater. (L.) The outer membrane 
which incloses the brain, 82. 
Dyspepsia, treatment of, 205. 
Ear tube, 139. 
Education of the muscles, 75. 
Effect of oxygen in respiration, 265. 
Elements of nutrition, 271. 
“ “ respiration. 272. 
Employment as indicating the kind of 
food, 203. 
Enamel of the teeth, 189. 
Epiglot'tis. (Gr. over the glottis.) The 
cartilage that covers the glottis in 
swallowing. 254. 
Epiph'ysis. (Gr. E7ti, upon, and <pva), 
to grow.) A prominence of bone. 
Esoph'agus. (Gr. oiiO<p(xyoi, the 
gullet.) 193. 
Eth'moid. (Gr. ylj/uo$, a sieve.) A 
bone of the cranium. 18. 
Eusta'chian tube, 140. 
Exercise, 296. 
“ of the brain, 97. 
Excrementi'tious, that which is useless 
in the system. 
External ear, 138. 
“ parts of the eye, 125. 
Extravasation of blood, the escape of 
blood from its proper vessels into the 
cellular tissue. 
Expiration, the act of expelling air from 
the lungs. 
Eye, adaptation to different distances, 
1:33. 
Eye, as related to light, 128. 
“ “ “ intensity of light, 132. 
“ how improved or injured, 137. 
Eye ids, 125. 
Farina'ceous, consisting of farina, 
starch. /INDEX AND GLOSSARY. 
251 
Fas'cia. (L.) A band of tendinous 
substance- 
Facial (pertaining to the face) nerve, 
Fasci'culus. (L. a small bundle.) A 
collection of minute muscular fibres. 
08. 
Falx. (L. a pruning-hook.) Applied, 
from their form, to two folds of the 
dura mater, 82. 
Feeling, location, 162. 
subject to training, 108. 
“ superiority to other senses, 169. 
“ uses, 167. 
Fe'mur, 50. 
Fenes'tra. (L. a window.) The open- 
ings into the labyrinth. 140. 
Fib'rin of the blood, 233. 
Fib'ula, 52. 
Flexion, the act of bending. 
Follicles, 284. 
Food, 176, 300. 
Fora'men, plural foramina. (L.) An 
aperture. 
Forces of the circulation, 244. 
Form of the bones, 8. 
Formation of chyle, 222. 
Forms of the muscles, 70. 
Fos'sa. (L. a trench.) A depression in 
the base of the cranium. 19. 
Frontal bone, 13. 
“ sinuses, 13. 
Function, office or duty, purpose. 
Functions of the brain, 90. 
“ “ gray substance, 107. 
“ “ white substance, 105. 
“ “ nerves, 117. 
Gangdion, 113. 
Gastric juice, 197. 
Gel'atine, an animal product, soluble in 
water,'glue. 
Gland, an organ of secretion, 283. 
Glosso-pharynx, belonging in common 
to the tongue (glossa) and the pharynx. 
Glot'tis, the opening into the larynx. 
Fig. 103. 
Glu'ten, the tough substance obtained 
from wheat by chewing the kernels. 
Great sympathetic nerve, 116. 
Growth of the body, 269. 
“ “ bones, 10. 
“ “ the teeth, 185. 
Hand, as an organ of prehension, 49. 
Hearing, 138. 
“ cause of the sensation, 143. 
“ conditions of perfect, 147. 
“ interference with, 148. 
Heart, 235. 
Hemispheres of the cerebrum, 95. 
Hepat'ic, pertaining to the liver. 
Herbiv'orous, a term applied to animals 
which require vegetable food. 
Hinge joint, 63. 
Hu'merus, 46. 
Hydraulic, relating to the conveyance 
of liquids. 
Hy'drogen, one of the elements of water. 
Hyoid (U-shaped> bone, 30. 
Hypo-glos'sus. (Gr. vito, under.) Un- 
der the tongue, one of the cranial 
nerves, 111. 
Immovable joints, 61. 
Incisor (cutting), the sharp front teeth, 
180. 
In'cubus (nightmare), 174. 
Incus. (L. an anvil.) The name of one 
of the bones of the ear, 140. 
Injury of the arteries, 247. 
Insertion of the muscles, 08. 
Intestines, 223. 
Internal parts of the eye, 126. 
Intervertebral foramina, 35. 
Involuntary muscles, 66. 
Iris, 126. 
Iron in the blood, 266. 
Joints, 56. 
Kidneys, 290. 
Kinds of food, 201. 
Labyrinth, 141. 
Lachrymal bones, 23. 
“ glands, 125. 
Lacteals, 274. 
Lacteal absorption, 226. 
Large intestine, 230. 
La'rynx, 254. 
Ligaments, 59. 
Liquid food, 206. 
Liquor of Cotun'nius, 142. 
Liver, 216. 
Lobes of the brain, 85. 
“ “ lungs, 255. 
Locomotion, motion from place to place. 
Long-sightedness, 130. 
Lower maxillary bone, 29. 
“ spongy bones, 27. 
Lumbar, pertaining to the loins. 
Lungs, 254. 
Lymphatic vessels, 276. 
Mag'num foramen. (L.) The larger 
aperture in the bone of the cranium 
through which the spinal cord enters, 
15. 
Malar. (L. mala, the cheek.) Pertain- 
ing to the cheek. 25. 
Mal'leus. (L. a hammer.) The first 
bone of the tympanum. 140. 
Mastica'tion. (L. mastica'tio.) The act 
of chewing. 183. 
Mastoid. (Gr. /ta?ro?, nipple.) For- 
amen. 10. 
Maxillary (L. max'iUa), or jawbone, 24, 
29. 
Mechanical system, 5. 
“• “ __ why necessary, 3. 252 
INDEX AND GLOSSARY. 
Medias'tinum. (L. mediug, the middle, 
and Gr. TEivoo, to stretch.) A double 
partition through the thorax from the 
spine to the sternum, 253. 
Medul'la oblonga'ta. (L. the pith, pro- 
longed.) The portion of the spinal 
cord within the cranium, 86. 
Membrane, permeability of, 203. 
Membranes of the brain, 82. 
Mes'entery. (Gr. /UEiEvtEpiov.) The 
membrane to which the small intes- 
tine is attached. 224. 
Metacarpal. (Gr. fiEra, beyond, and 
xapito?, the wrist.) 48. 
Metatarsal. (Gr. beyond the heel.) Per- 
taining to that part between the in- 
step and the toes. 54. 
Mias'ma. (Gr.) Infecting substance in 
the air. 
Mitral valves, the valves in the second 
ventricle of the heart, 237. 
Mo'lar, (L. mold, a mill.) A grinding 
tooth. 186. 
Mo'tor oc'uli. (L.) The name of the 
third cranial nerve. 111. 
Movable joints, 62. 
Mu'cus. a viscid secretion from mucous 
membranes. 
Muscles, 66. 
Muscular fibre, 68. 
Muscular power dependent on the cir- 
culation of the blood, 78. 
Muscular power dependent on the ner- 
vous influence, 79. 
Nasal, pertaining to the nose. 
Nasal bones, 22. 
Nature of muscular power, 76. 
“ “ secretion, 282. 
Nerves, 110. 
“ as sentinels, 120. 
“ afferent, 105. 
“ efferent, 105. 
“ rendered insensible, 120. 
“ of special sensibility, 117. 
“ general sensibility. 118. 
“ voluntary motion, 123. 
“ involuntary motion, 124. 
Nervous system, why necessary, 3. 
Nitrogen, a chemical element, a con- 
stituent of the atmosphere. 
Nitrogenized constituents of the food, 
202. 
Nutrition, 250. 
“ elements of, 202. 
Object of the bones, 5, 
“ “ lymphatics, 277. 
Objects of perspiration, 286. 
“ “ secretion, 281. 
Oc'ciput. (L. ob and caput.) The back 
part of the head. 
Occipital bone, 15. 
Odors, 152. 
OiecTanon. (Gr. the elbow.) 47, 
Olfactory nerve, 151. 
Optic, pertaining to the eye. 
Orbicular muscles. 
Orbit of the eye, the bony cavity in 
which it is lodged, 125. 
Origin of the muscles, 68.- 
“ “ spinal nerves, 113. 
Oxygen consumed by respiration, 264. 
Os. (L.) Bone. 
Osseous, relating to the bones. 
Ossification, the act of becoming bone, 
6. 
Os'sa innominata. (L. bones not 
named.) The bones of the pelvis. 42. 
Ovoid, resembling (ovum) an egg. 
Palatine bones, 26. 
Pan'creas. (Gr. itav , all, and KpeaS, 
flesh.) 219. 
Pancreatic juice, 220. 
Papilla. (L.) A small elevation, 156. 
Parietal (L. paries, a wall) bones, 14. 
Parotid. (Gr. Ttapa, near, and OV?t 
the ear.) 190. 
Partial sleep, 173. 
Par vagum. (L. the wandering pair of 
nerves.) 111. 
Patel'la. (L.) The knee-pan* 53. 
Pelvis. (L. a basin.) 41. 
“ objects of the, 43. 
Penniform muscles, 70. 
Pepsine, 199. 
Pericar'dium. (Gr. heart envelope.) 
235. 
Perios'teum, 11. 
Peritone'um. (Gr. Ttspt, around, and 
TEivoo, to extend.) The lining mem- 
brane of the abdomen, 183. 
Perspiration, 285. 
Petrous. (Gr. TtErpoZ, stone.) Hard, 
like stone. 
Phal'anx. (Gr. a row, a portion of an 
army, pi. phalanges.) 
Pha'rynx. (Gr.) The upper part of the 
esophagus. 192. 
Phenomenon. (Gr.) PI. phenomena. 
What is observed. 
Phosphate of lime, one of the constitu- 
ents of bone, 7. 
Physiology, objects of, 1. 
Pi'a mater. (L.) The inner membrane 
of the brain, 84. 
Plates of the cranium, 12. 
Pleura. (Gr. the side.) The membrane 
which lines the thorax and covers the 
lungs. 253. 
Plexus. (L. a network.) 114. 
Pons. (L. a bridge.) Varolii, the upper 
part of the medulla oblongata. 80. 
Portal system, 216. 
Pronation. (L. promts, having the face 
bent downward.) The act of turning 
the hand so that the palm will bo 
downward. 49. 253 
Prehension. (L. prehensio, laying hold 
of.) The act or the power of holding. 
49. 
Process. (L.) A prominence on the 
bones. 
Pter'ygoid. (Gr. TCTEfiOV, a wing.) 
Wing-like. 
Pulmonary. (L. pulmo, the lungs.) 
Pertaining to the lungs. 
Pulse. (L. pello. to beat.) 247. 
Punc'ta lachryma'lia. (L.) The capil- 
lary tubes through which the lachry- 
mal secretion escapes. 125. 
Pupil. (L.) 126. 
Pyloric. (Gr. TtvXrj, a gate.) Orifice. 
196. 
Quantity of food, 209. 
Ra'dius. (L.) A bone of the forearm. 47. 
Reg'imen. (L.) The regulation of diet. 
Relation of the secreting organs to each 
other, 293. 
Repairing system, 176. 
“ “ why necessary, 3. 
Respiration, 253. 
“ elements of, 202. [258. 
“ upon what it depends, 40, 
“ object of, 261. 
“ frequency of, 264. 
Ee'te muco'sum. (L. mucous network.) 
That portion of the cuticle in which 
the coloring matter is found. 163. 
Re'tina. (L. dim. of rete.) 126. 
Ribs, 39. 
Sacrum, the principal bone at the base 
of the spine, 31. 
Sacral, belonging to the sacrum. 
Sali'va, the viscid secretion of the 
mouth, 190. 
Salivary glands, 190. 
Sapid substances, 157. 
Scap'ula. (L.) 44. 
Sciatic, pertaining to the hip. 
Schneide'rian membrane, 150. 
Sclerotic. (Gr. iKXrjpoZy firm.) Coat 
of the eye. 126. 
Secretion, 281. 
“ from glands, 289. 
“ “ surfaces, 283. 
Semi-circular canals. 141. 
Semi-lunar valves, 239. 
Sensation. 93. 
Sense of feeling, 162. 
“ “ hearing, 138. 
“ “ sight, 125. 
“ “ smell, 149. 
“ “ taste, 156. 
Se'rum. (L.) An ingredient in the 
blood. 233. 
Se'rous membrane, one which secretes 
a fiuid resembling serum. 
Short-sightedness, 135. 
Sighing, 260. 
INDEX AND GLOSSARY. 
Sigmoid (crooked, like the Greek letter 
5), 46. 
Sinus. (L. a bag.) A cavity. 
Skeleton, the bones of the body arranged 
in their proper order. 
Sleep, 170. 
Small intestine, 223. 
Smelling, location, 149. 
“ means of increasing the sense, 
153. 
Smelling, uses of. 154. 
Solidity cognized by sight, 134. 
Spherical aberration. 131. 
Sphenoid (Gr. icpr/v, a wedge) 
bone, 17. 
Spine, 31. 
Spinal canal, 36. 
“ cord, 104. 
“ nerves, 112. 
“ structure, 113. 
“ distribution, 114. 
“ interchange of lilaments, 115. 
Spleen, 291. 
Squinting, 136. 
Sta'pes. (L. a stirrup.) The last hone 
of the tympanum, 140. 
Starvation, 269, 
Sternum, 38. 
Stomach, 196. 
Structure of the bones. 9. 
“ “ hair, 164. 
“ “ heart, 2:35. 
“ “ nails, 165. 
“ “ skin, 166. 
Styloid. (L. stylus, a writing-stick.) 
Resembling a stylus. 
Suture, 20. 
Subcla'vian. (L. sub. under.) Name of 
organs under the clavicle. 241. 
Sublingual (L. lingua, the tongue) 
gland. 190. 
Suboccipital nerve, 112. 
Submaxi llary gland, 190. 
Supination. (L. supinus, with the face 
upward.) The hand so turned as to 
bring the palm upward. 49. 
Synovia. (Gr. 5w, like, and L. ovum, 
an egg.) A fluid like the white of an 
egg. 60. 
Synovial membrane. 60. 
Tarsal (Gr. rap?o?, the middle and 
back part of the foot) bones, those 
which form the tarsus. 54. 
Tartar, 188. 
Taste, classification, 159. 
“ importance, 160. 
“ uses, 161. 
Tea and coffee, use of, 206. 
Teeth, 184. 
“ care of the, 187. 
“ as indicating the kind of food, 
203. 
Temporal bones, 16, INDEX AND GLOSSARY. 
Tendons, 69. 
Teuto'rium. (L.) The membrane which 
separates the cerebrum from the cere- 
bellum. 82. 
Thorax, the upper cavity of the trunk, 
253. 
Thorax, objects of, 40. 
Thoracic (contained in the thorax) 
duct, 226. 
Thymus gland, 291. 
Thyroid gland, 291. 
Thyroid cartilage, 254. 
Tibia. (L. a flute.) Large bone of the 
leg. 51. 
Times ol taking food, 211. 
Tissues, any of the organized substances 
oi the body. 
Tongue. 191. 
Tonsils, a mass of follicles on each side 
the entrance of the pharynx, note 5f. 
Trachea. (Gr. Tpaxvi, rough.) The 
air-passage to the lungs. 255. 
Tricuspid. (L. tres, three, and cuspis, a 
point.) The three pointed valves at 
the orifice between the right auricle 
and ventricle. 237. 
Trigera'ini. (L.) Nerve. 111. 
Trochan'ter, (Gr.) The large processes 
ol the femur. 50. 
Trochlea'ris. (L. trochlea, a pulley.) A 
nerve which goes to the superior 
oblique muscle ot the eye, so named 
because that muscle passes through a 
pulley near the inner corner of the 
eye. 
True skin, 166. 
Tym'panum. (L. a drum.) Part ot the 
ear. 140. 
Ulna. (L. the arm.) The principal bone 
of the arm. 47. 
Unguents, 280. 
Upper maxillary bones, 24. 
Use of the blood-cells, 231. 
Uses of the cranium, 21. 
“ *• foot, 55. 
“ “ pelvis, 43. 
“ “ spine, 37. 
Valves of the arteries, 239. 
“ “ heart, 237. 
“ “ veins, 242. 
Vegetable food, 203. 
Vegetation the source of all food, 203. 
Veins, 242. 
“ as absorbents, 275. 
Ve'lum pala'ti, 194. 
Ventilation, 262. 
Ventricles of the brain, 88. 
“ “ glottis, 254. 
“ “ heart, 236. 
Vermicular motion of the intestines, 
225. 
Vertebra, 32. 
Ver'iebrse, processes of the, 32. 
“ cartilages of the, 34. 
“ differences in, 33. 
Ves'tibule, 141. 
Viscus. (L.) An organ contained in 
any of the cavities of the body, pi. 
viscera. 
Vision, erect, 129. 
“ single. 130. 
Vital force, 267. 
Vitreous humor, 127. 
Vocal cords, 254. 
Voice, 254. 
Voluntary muscles, 67. 
Vomer. (L. a ploughshare.) 28. 
Waste in the system, 176. 
Water, 299. 
Yawning, 260. 
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LATIN DICTIONARY. 
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In this American edition of a valuable English work is appended 
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need be, comprising a iudicious selection of materials, easily yet effectually 
wrought. The author attempts just as much as he ought to, and does well all 
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love of genius and its works which thoroughly pervades it, and makes it just 
what you want to put in a pupil’s hands.”—J. H. Raymond, President of Vas- 
sar Female College. 
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from the trial which I have now made of it, 1 have every reason to congratu- 
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Shaw’s Specimens of English Literature. A Companion 
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