Chapter XV: Experimental Work in Physiology (1)

406. The Limitations of Experimental Work in Physiology in Schools. Unlike other branches of science taught in the schools from the experimental point of view, the study of physiology has its limitations. The scope and range of such experiments is necessarily extremely limited compared with what may be done with the costly and elaborate apparatus of the medical laboratory. Again, the foundation of physiology rests upon systematic and painstaking dissection of the dead human body and the lower animals, which mode of study very properly is not permitted in ordinary school work. Experiments upon the living human body and the lower animals, now so generally depended upon in our medical and more advanced scientific schools, for obvious reasons can be performed only in a crude and quite superficial manner in secondary schools.

Hence in the study of physiology in schools many things must be taken for granted. The observation and experience of medical men, and the experiments of the physiologist in his laboratory must be depended upon for data which cannot be well obtained at first hand by young students.

407. Value of Experiments in Physiology in Secondary Schools. While circumstances and regard for certain proprieties of social life forbid the use of a range of experiments, in anatomy and physiology, such as are permitted in other branches of science in secondary schools, it by no means follows that we are shut out altogether from this most important and interesting part of the study. However simple and crude the apparatus, the skillful and enthusiastic teacher has at his command a wide series of materials which can be profitably utilized for experimental instruction. As every experienced teacher knows, pupils gain a far better knowledge, and keep up a livelier interest in any branch of science, if they see with their own eyes and do with their own hands that which serves to illuminate and illustrate the subject-matter.

Note. For additional suggestions and practical helps on the subject of experimental work in physiology the reader is referred to Blaisdell’s _How to Teach Physiology_, a handbook for teachers. A copy of this pamphlet will be sent postpaid to any address by the publishers of this book on receipt of ten cents.

The experimental method of instruction rivets the attention and arouses and keeps alive the interest of the young student; in fact, it is the only true method of cultivating a scientific habit of study[57]. The subject-matter as set forth on the printed pages of this book should be mastered, of course, but at the same time the topics discussed should be illuminated and made more interesting and practical by a well-arranged series of experiments, a goodly show of specimens, and a certain amount of microscopical work.

408. The Question of Apparatus. The author well understands from personal experience the many practical difficulties in the way of providing a suitable amount of apparatus for classroom use. If there are ample funds for this purpose, there need be no excuse or delay in providing all that is necessary from dealers in apparatus in the larger towns, from the drug store, markets, and elsewhere. In schools where both the funds and the time for such purposes are limited, the zeal and ingenuity of teachers and students are often put to a severe test. Fortunately a very little money and a great deal of ingenuity and patience will do apparent wonders towards providing a working supply of apparatus.

It will be noticed that many of the experiments in the preceding chapters of this book can be performed with very simple, and often a crude and home-made sort of apparatus. This plan has been rigidly followed by the author, first, because he fully realizes the limitations and restrictions of the subject; and secondly, because he wishes to emphasize the fact that expensive and complicated apparatus is by no means necessary to illustrate the great principles of anatomy and physiology.

409. Use of the Microscope. To do thorough and satisfactory work in physiology in our higher schools a compound microscope is almost indispensable. Inasmuch as many of our best secondary schools are equipped with one or more microscopes for use in other studies, notably botany, it is much less difficult than it was a few years ago to obtain this important help for the classes in physiology.

Illustration: Fig. 170.—A Compound Microscope

For elementary class work a moderate-priced, but well-made and strong, instrument should be provided. If the school does not own a microscope, the loan of an instrument should be obtained for at least a few weeks from some person in the neighborhood.

The appearance of the various structures and tissues of the human body as revealed by the microscope possesses a curious fascination for every observer, especially for young people. No one ever forgets the first look at a drop of blood, or the circulation of blood in a frog’s foot as shown by the microscope.

Note. For detailed suggestions in regard to the manipulation and use of
the microscope the student is referred to any of the standard works on
the subject. The catalogues of scientific-instrument makers of our
larger cities generally furnish a list of the requisite materials or
handbooks which describe the use of the various microscopes of standard
make.
The author is indebted to Bergen’s _Elements of Botany_ for the
following information concerning the different firms which deal in
microscopes. “Several of the German makers furnish excellent
instruments for use in such a course as that here outlined. The
author is most familar with the Leitz microscopes, which are
furnished by Wm. Krafft, 411 West 59th St., New York city, or by
the Franklin Educational Co., 15 and 17 Harcourt St., Boston. The
Leitz Stand, No. IV., can be furnished duty free (for schools
only), with objectives 1, 3, and 5, eye-pieces I. and III., for
$24.50. If several instruments are being provided, it would be well
to have part of them equipped with objectives 3 and 7, and
eye-pieces I. and III.
“The American manufacturers, Bausch & Lomb Optical Company,
Rochester, N.Y., and No. 130 Fulton St., New York city, have this
year produced a microscope of the Continental type which is
especially designed to meet the requirements of the secondary
schools for an instrument with rack and pinion coarse adjustment
and serviceable fine adjustment, at a low price. They furnish this
new stand, ‘AAB,’ to schools and teachers at ‘duty-free’ rates, the
prices being for the stand with two eye-pieces (any desired power),
⅔-inch and ¼-inch objectives, $25.60, or with 2-inch, ⅔-inch, and
¼-inch objectives, and two eye-pieces, $29.20. Stand ‘A,’ the same
stand as the ‘AAB,’ without joint and with sliding tube coarse
adjustment (as in the Leitz Stand IV.), and with three eye-pieces
and ⅔-inch and ¼-inch objectives, is furnished for $20.40. Stand
‘A,’ with two eye-pieces, ⅔-inch and ⅙-inch objectives, $20.40.”

410. The Use of the Skeleton and Manikin. The study of the bones by the help of a skeleton is almost a necessity. To this intent, schools of a higher grade should be provided both with a skeleton and a manikin. If the former is not owned by the school, oftentimes a loan of one can be secured of some medical man in the vicinity. Separate bones will also prove useful. In fact, there is no other way to study properly the structure and use of the bones and joints than by the bones themselves. A good manikin is also equally serviceable, although not so commonly provided for schools on account of its cost.

411. The Question of Vivisection and Dissection. There should be no question at all concerning vivisection. _In no shape or form should it be allowed in any grade of our schools._ Nor is there any need of much dissection in the grammar-school grades. A few simple dissections to be performed with fresh beef-joints, tendons of turkey legs, and so on, will never engender cruel or brutal feelings toward living things. In the lower grades a discreet teacher will rarely advise his pupils to dissect a dead cat, dog, frog, or any other animal. Instead of actual dissection, the pupils should examine specimens or certain parts previously dissected by the teacher,—as the muscles and tendons of a sheep, the heart of an ox, the eye of a codfish, and so on. Even under these restrictions the teacher should not use the knife or scissors before the class to open up any part of the specimen. In brief, avoid everything that can possibly arouse any cruel or brutal feeling on the part of young students.

In the higher schools, in normal and other training schools, different conditions prevail. Never allow vivisection in any form whatever, either in school or at home. Under the most exact restrictions students in these schools may be taught to make a few simple dissections.

Most teachers will find, however, even in schools of a higher grade, that the whole subject is fraught with many difficulties. It will not require much oftentimes to provoke in a community a deal of unjust criticism. A teacher’s good sense and discretion are often put to a severe test.

Additional Experiments.

To the somewhat extended list of experiments as described in the preceding chapters a few more are herewith presented which may be used as opportunity allows to supplement those already given.

Experiment 193. _To examine white fibrous tissue._ Snip off a very minute portion from the muscle of a rabbit, or any small animal recently dead. Tease the specimen with needles, mount in salt solution and examine under a high power. Note the course and characters of the fibers.

Experiment 194. _To examine elastic tissue._ Tease out a small piece of ligament from a rabbit’s leg in salt solution; mount in the same, and examine as before. Note the curled elastic fibers.

Experiment 195. _To examine areolar tissue._ Gently tease apart some muscular fibers, noting that they are attached to each other by connective tissue. Remove a little of this tissue to a slide and examine as before. Examine the matrix with curled elastic fiber mixed with straight white fibers.

Experiment 196. _To examine adipose tissue._ Take a bit of fat from the mesentery of a rabbit. Tease the specimen in salt solution and mount in the same. Note the fat cells lying in a vascular meshwork.

Experiment 197. _To examine connective tissues._ Take a very small portion from one of the tendons of a rabbit, or any animal recently dead; place upon a glass slide with a drop of salt solution; tease it apart with needles, cover with thin glass and examine with microscope. The fine wavy filaments will be seen. Allow a drop of dilute acetic acid to run under the cover glass; the filaments will swell and become transparent.

Experiment 198. Tease out a small piece of ligament from the rabbit’s leg in salt solution; mount in the same, and examine under a high power. Note the curled elastic fibers.

Experiment 199. _A crude experiment to represent the way in which a person’s neck is broken._ Bring the ends of the left thumb and the left second finger together in the form of a ring. Place a piece of a wooden toothpick across it from the middle of the finger to the middle of the thumb. Put the right forefinger of the other hand up through the front part to represent the odontoid process of the axis, and place some absorbent cotton through the other part to represent the spinal cord. Push backwards with the forefinger with just enough force to break the toothpick and drive its fragments on to the cotton.

Experiment 200. _To illustrate how the pulse-wave is transmitted along an artery._ Use the same apparatus as in Experiment 106, p. 201. Take several thin, narrow strips of pine wood. Make little flags by fastening a small piece of tissue paper on one end of a wooden toothpick. Wedge the other end of the toothpick into one end of the strips of pine wood. Use these strips like levers by placing them across the long rubber tube at different points. Let each lever compress the tube a little by weighting one end of it with a blackboard eraser or book of convenient size. As the pulse-wave passes along under the levers they will be successively raised, causing a slight movement of the tissue-paper flags.

Experiment 201. _The dissection of a sheep’s heart._ Get a sheep’s
heart with the lungs attached, as the position of the heart will be
better understood. Let the lungs be laid upon a dish so that the heart
is uppermost, with its apex turned toward the observer.
The line of fat which extends from the upper and left side of the
heart downwards and across towards the right side, indicates the
division between the right and left ventricles.
Examine the large vessels, and, by reference to the text and
illustrations, make quite certain which are the _aorta_, the
_pulmonary artery_, the _superior_ and _inferior venæ cavæ_, and
the _pulmonary veins_.
Tie variously colored yarns to the vessels, so that they may be
distinguished when separated from the surrounding parts.
Having separated the heart from the lungs, cut out a portion of the
wall of the _right ventricle_ towards its lower part, so as to lay
the cavity open. Gradually enlarge the opening until the _chordæ
tendineæ_ and the flaps of the _tricuspid valve_ are seen. Continue
to lay open the ventricle towards the pulmonary artery until the
_semilunar valves_ come into view.
The pulmonary artery may now be opened from above so as to display
the upper surfaces of the semilunar valves. Remove part of the wall
of the right auricle, and examine the right auriculo-ventricular
opening.
The heart may now be turned over, and the _left ventricle_ laid
open in a similar manner. Notice that the mitral valve has only two
flaps. The form of the valves is better seen if they are placed
under water, and allowed to float out. Observe that the walls of
the _left_ ventricle are much thicker than those of the _right_.
Open the left auricle, and notice the entrance of the _pulmonary
veins_, and the passage into the ventricle.
The ventricular cavity should now be opened up as far as the aorta,
and the semilunar valves examined. Cut open the aorta, and notice
the form of the _semilunar valves_.

Experiment 202. _To show the circulation in a frog’s foot_ (see Fig.
78, p. 192). In order to see the blood circulating in the membrane of a
frog’s foot it is necessary to firmly hold the frog. For this purpose
obtain a piece of soft wood, about six inches long and three wide, and
half an inch thick. At about two inches from one end of this, cut a
hole three-quarters of an inch in diameter and cover it with a piece of
glass, which should be let into the wood, so as to be level with the
surface. Then tie up the frog in a wet cloth, leaving one of the hind
legs outside. Next, fasten a piece of cotton to each of the two longest
toes, but not too tightly, or the circulation will be stopped and you
may hurt the frog.
Tie the frog upon the board in such a way that the foot will just
come over the glass in the aperture. Pull carefully the pieces of
cotton tied to the toes, so as to spread out the membrane between
them over the glass. Fasten the threads by drawing them into
notches cut in the sides of the board. The board should now be
fixed by elastic bands, or by any other convenient means, upon the
stage of the microscope, so as to bring the membrane of the foot
under the object glass.
The flow of blood thus shown is indeed a wonderful sight, and never
to be forgotten. The membrane should be occasionally moistened with
water.
Care should be taken not to occasion any pain to the frog.

Experiment 203. _To illustrate the mechanics of respiration_[58] (see Experiment 122, p. 234). “In a large lamp-chimney, the top of which is closed by a tightly fitting perforated cork (A), is arranged a pair of rubber bags (C) which are attached to a Y connecting tube (B), to be had of any dealer in chemical apparatus or which can be made by a teacher having a bunsen burner and a little practice in the manipulation of glass (Fig. 171). From the center of the cork is attached a rubber band by means of a staple driven through the cork, the other end of which (D) is attached to the center of a disk of rubber (E) such as dentists use. This disk is held to the edge of the chimney by a wide elastic band (F). There is a string (G) also attached to the center of the rubber disk by means of which the diaphragm may be lowered. Such is a description of the essentials of the model. The difficulties encountered in its construction are few and easily overcome. In the first place, the cork must be air-tight, and it is best made so by pouring a little melted paraffin over it, care being taken not to close the tube. The rubber bags were taken from toy balloon-whistles. In the construction of the diaphragm, it is to be remembered that it also must be air-tight, and in order to resemble the human diaphragm, it must have a conical appearance when at rest. In order to avoid making any holes in the rubber, the two attachments (one of the rubber band, and the other of the string) were made in this wise: the rubber was stretched over a button having an eye, then under the button was placed a smaller ring from an old umbrella; to this ring was attached the rubber band, and to the eye of the button was fastened the operating string. When not in use the diaphragm should be taken off to relieve the strain on the rubber band.”

Illustration: Fig. 171.

Experiment 204. _To illustrate the action of the intercostal muscles_ (see sec. 210). The action of the intercostal muscles is not at first easy to understand; but it will be readily comprehended by reference to a model such as that represented in Fig. 172. This maybe easily made by the student himself with four laths of wood, fastened together at the corners, A, B, C, D, with pins or small screws, so as to be movable. At the points E, F, G, H, pins are placed, to which elastic bands may be attached (A). B D represents the vertebral column; A C, the sternum; and A B and C D, the ribs. The elastic band F G represents the _external_ intercostal muscles, and E H, the _internal_ intercostals. If now the elastic band E H be removed, the remaining band, F G, will tend to bring the two points to which it is attached, nearer together, and the result will be that the bars A B and C D will be drawn upwards (B), that is, in the same direction as the ribs in the act of _inspiration_. When the elastic band E H is allowed to exert its force, the opposite effect will be produced (C); in this case representing the position of the ribs in an act of _expiration_.

Illustration: Fig. 172.

Experiment 205. Pin a round piece of bright red paper (large as a dinner-plate) to a white wall, with a single pin. Fasten a long piece of thread to it, so it can be pulled down in a moment. Gaze steadily at the red paper. Have it removed while looking at it intently, and a greenish spot takes its place.

Experiment 206. Lay on different parts of the skin a small, square piece of paper with a small central hole in it. Let the person close his eyes, while another person gently touches the uncovered piece of skin with cotton wool, or brings near it a hot body. In each case ask the observed person to distinguish between them. He will always succeed on the volar side of the hand, but occasionally fail on the dorsal surface of the hand, the extensor surface of the arm, and very frequently on the skin of the back.

Experiment 207. _Wheatstone’s fluttering hearts_. Make a drawing of a red heart on a bright blue ground. In a dark room lighted by a candle hold the picture below the level of the eyes and give it a gentle to-and-fro motion. On continuing to look at the heart it will appear to move or flutter over the blue background.

Experiment 208. At a distance of six inches from the eyes hold a veil or thin gauze in front of some printed matter placed at a distance of about two feet. Close one eye, and with the other we soon see either the letters distinctly or the fine threads of the veil, but we cannot see both equally distinct at the same time. The eye, therefore, can form a distinct image of a near or distant object, but not of both at the same time; hence the necessity for accommodation.

Experiment 209. Place a person in front of a bright light opposite a window, and let him look at the light; or place one’s self opposite a well-illuminated mirror. Close one eye with the hand and observe the diameter of the other pupil. Then suddenly remove the hand from the closed eye: light falls upon it; at the same time the pupil of the other eye contracts.

Experiment 210. _To illustrate the blind spot. Marriott’s experiment_. On a white card make a cross and a large dot, either black or colored. Hold the card vertically about ten inches from the right eye, the left being closed. Look steadily at the cross with the right eye, when both the cross and the circle will be seen. Gradually approach the card toward the eye, keeping the axis of vision fixed on the cross. At a certain distance the circle will disappear, _i.e._, when its image falls on the entrance of the optic nerve. On bringing the card nearer, the circle reappears, the cross, of course, being visible all the time (see Experiment 180, p. 355).

Experiment 211. _To map out the field of vision_. A crude method is to place the person with his back to a window, ask him to close one eye, stand in front of him about two feet distant, hold up the forefingers of both hands in front of and in the plane of your own face. Ask the person to look steadily at your nose, and as he does so observe to what extent the fingers can be separated horizontally, vertically, and in oblique directions before they disappear from his field of vision.

Experiment 212. _To illustrate imperfect judgment of distance_. Close
one eye and hold the left forefinger vertically in front of the other
eye, at arm’s length, and try to strike it with the right forefinger.
On the first trial one will probably fall short of the mark, and
fail to touch it. Close one eye, and rapidly try to dip a pen into
an inkstand, or put a finger into the mouth of a bottle placed at a
convenient distance. In both cases one will not succeed at first.
In these cases one loses the impressions produced by the
convergence of the optic axes, which are important factors in
judging of distance.

Experiment 213. Hold a pencil vertically about twelve inches from the nose, fix it with both eyes, close the left eye, and then hold the right index finger vertically, so as to cover the lower part of the pencil. With a sudden move, try to strike the pencil with the finger. In every case one misses the pencil and sweeps to the right of it.

Experiment 214. _To illustrate imperfect judgment of direction_. As the retina is spherical, a line beyond a certain length when looked at always shows an appreciable curvature. Hold a straight edge just below the level of the eyes. Its upper margin shows a slight concavity.

Surface Anatomy and Landmarks.

In all of our leading medical colleges the students are carefully and thoroughly drilled on a study of certain persons selected as models. The object is to master by observation and manipulation the details of what is known as surface anatomy and landmarks. Now while detailed work of this kind is not necessary in secondary schools, yet a limited amount of study along these lines is deeply interesting and profitable. The habit of looking at the living body with anatomical eyes and with eyes at our fingers’ ends, during the course in physiology, cannot be too highly estimated.

In elementary work it is only fair to state that many points of surface anatomy and many of the landmarks cannot always be defined or located with precision. A great deal in this direction can, however, be done in higher schools with ingenuity, patience, and a due regard for the feelings of all concerned. Students should be taught to examine their own bodies for this purpose. Two friends may thus work together, each serving as a “model” to the other.

To the following syllabus may be added such other similar exercises as ingenuity may suggest or time permit.

Syllabus.

I. Bony Landmarks.

1. The _occipital protuberance_ can be distinctly felt at the back of the head. This is always the thickest part (often three-quarters of an inch or more) of the skull-cap, and is more prominent in some than in others. The thinnest part is over the temples, where it may be almost as thin as parchment.

2. The working of the _condyle of the lower jaw_ vertically and from side to side can be distinctly felt and seen in front of the ear. When the mouth is opened wide, the condyle advances out of the glenoid cavity, and returns to its socket when the mouth is shut. In front of the ear, lies the zygoma, one of the most marked and important landmarks to the touch, and in lean persons to the eye.

3. The sliding movement of the _scapula_ on the chest can be properly understood only on the living subject. It can move not only upwards and downwards, as in shrugging the shoulders, backwards and forwards, as in throwing back the shoulders, but it has a rotary movement round a movable center. This rotation is seen while the arm is being raised from the horizontal to the vertical position, and is effected by the cooperation of the trapezius with the serratus magnus muscles.

4. The _patella_, or knee-pan, the _two condyles of the tibia_, the _tubercle on the tibia_ for the attachment of the ligament of the patella, and the _head of the fibula_ are the chief bony landmarks of the knee. The head of the fibula lies at the outer and back part of the tibia. In extension of the knee, the patella is nearly all above the condyles. The inner border of the patella is thicker and more prominent than the outer, which slopes down toward its condyle.

5. The short, front edge of the _tibia_, called the “shin,” and the broad, flat, subcutaneous surface of the bone can be felt all the way down. The inner edge can be felt, but not so plainly.

6. The head of the _fibula_ is a good landmark on the outer side of the leg, about one inch below the top of the tibia. Note that it is placed well back, and that it forms no part of the knee joint, and takes no share in supporting the weight. The shaft of the fibula arches backwards and is buried deep among the muscles, except at the lower fourth, which can be distinctly felt.

7. The _malleoli_ form the great landmarks of the ankle. The outer malleolus descends lower than the inner. The inner malleolus advances more to the front and does not descend so low as the outer.

8. The line of the _clavicle_, or collar bone, and the projection of the joint at either end of it can always be felt. Its direction is not perfectly horizontal, but slightly inclined downwards. We can distinctly feel the _spine_ of the scapula and its highest point, the _acromion_.

9. Projecting beyond the acromion (the arm hanging by the side), we can feel, through the fibers of the _deltoid_, the upper part of the humerus. It distinctly moves under the hand when the arm is rotated. It is not the head of the bone which is felt, but its prominences (the tuberosities). The greater, externally; the lesser in front.

10. The _tuberosities of the humerus_ form the convexity of the shoulder. When the arm is raised, the convexity disappears,—there is a slight depression in its place. The head of the bone can be felt by pressing the fingers high up in the axilla.

11. The _humerus_ ends at the elbow in two bony prominences (internal and external condyles). The internal is more prominent. We can always feel the _olecranon_. Between this bony projection of the ulna and the internal condyle is a deep depression along which runs the ulna nerve (commonly called the “funny” or “crazy” bone).

12. Turn the hand over with the palm upwards, and the edge of the _ulna_ can be felt from the olecranon to the prominent knob (styloid process) at the wrist. Turn the forearm over with the palm down, and the head of the ulna can be plainly felt and seen projecting at the back of the wrist.

13. The upper half of the _radius_ cannot be felt because it is so covered by muscles; the lower half is more accessible to the touch.

14. The three rows of projections called the “knuckles” are formed by the proximal bones of the several joints. Thus the first row is formed by the ends of the metacarpals, the second by the ends of the first phalanges, and the third by the ends of the second phalanges. That is, in all cases the line of the joints is a little in advance of the knuckles and nearer the ends of the fingers.

II. Muscular Landmarks.

1. The position of the _sterno-mastoid_ muscle as an important and interesting landmark of the neck has already been described (p. 70).

2. If the left arm be raised to a vertical position and dropped to a horizontal, somewhat vigorously, the tapering ends of the _pectoralis major_ and the tendons of the _biceps_ and _deltoid_ may be felt by pressing the parts in the axilla between the fingers and thumb of the right hand.

3. The appearance of the _biceps_ as a landmark of the arm has already been described (p. 70). The action of its antagonist, the _triceps_, may be studied in the same manner.

4. The _sartorius_ is one of the fleshy landmarks of the thigh, as the biceps is of the arm, and the sterno-cleido-mastoid of the neck. Its direction and borders may be easily traced by raising the leg,—a movement which puts the muscle in action.

5. If the model be directed to stand on tiptoe, both of the large muscles of the calf, the _gastrocnemius_ and _soleus_, can be distinguished.

6. Direct the model, while sitting upright, to cross one leg over the other, using his utmost strength. The great muscles of the inner thigh are fully contracted. Note the force required to pull the legs to the ordinary position.

7. With the model lying in a horizontal position with both legs firmly held together, note the force required to pull the feet apart while the great muscles of the thigh are fully contracted.

8. In forcible and resisted flexion of the wrist two tendons come up in relief. On the outer side of one we feel the pulse at the wrist, the radial artery here lying close to the radius.

9. On the outer side of the wrist we can distinctly see and feel when in action, the three extensor tendons of the thumbs. Between two of them is a deep depression at the base of the thumb, which the French call the “anatomical tobacco box.”

10. The relative position of the several extensor tendons on the back of the wrist and fingers as they play in their grooves over the back of the radius and ulna can be distinctly traced when the several muscles are put in action.

11. There are several strong tendons to be seen and felt about the ankle. Behind is the _tendo Achillis_. It forms a high relief with a shallow depression on each side of it. Behind both the inner and outer ankle several tendons can be felt. Over the front of the ankle, when the muscles are in action, we can see and feel several tendons. They start up like cords when the action is resisted. They are kept in their proper relative position by strong pulleys formed by the annular ligament. Most of these tendons can be best seen by stand a model on one foot, _i.e._ in unstable equilibrium.

III. Landmarks of the Heart.

To have a general idea of the form and position of the _heart_, map its outline with colored pencils or crayon on the chest wall itself, or on some piece of clean, white cloth, tightly pinned over the clothing. A pattern of the heart may be cut out of pasteboard, painted red, or papered with red paper, and pinned in position outside the clothing. The apex of the heart is at a point about two inches below the left nipple and one inch to its sternal side. This point will be between the fifth and sixth ribs, and can generally be determined by feeling the apex beat.

IV. Landmarks of a Few Arteries.

The pulsation of the _temporal_ artery can be felt in front of the ear, between the zygoma and the ear. The _facial_ artery can be distinctly felt as it passes over the upper jaw at the front edge of the masseter muscle. The pulse of a sleeping child can often be counted at the anterior fontanelle by the eye alone.

About one inch above the clavicle, near the outer border of the sterno-mastoid, we can feel the pulsation of the great _subclavian_ artery. At the back of the knee the _popliteal_ artery can be felt beating. The _dorsal_ artery of the foot can be felt beating on a line from the middle of the ankle to the interval between the first and second metatarsal bones.

When the arm is raised to a right angle with the body, the _axillary_ artery can be plainly felt beating in the axilla. Extend the arm with palm upwards and the _brachial_ artery can be felt close to the inner side of the biceps. The position of the _radial_ artery is described in Experiment 102.

Glossary.

Abdomen (Lat. _abdo_, _abdere_, to conceal). The largest cavity of the body, containing the liver, stomach, intestines, and other organs.

Abductor (Lat. _abduco_, to draw from). A muscle which draws a limb from the middle line of the body, or a finger or toe from the middle line of the foot or hand.

Absorbents (Lat. _absorbere_, to suck up). The vessels which take part in the process of absorption.

Absorption. The process of sucking up nutritive or waste matters by the blood-vessels or lymphatics.

Accommodation of the Eye. The alteration in the shape of the crystalline lens, which accommodates, or adjusts, the eye for near or remote vision.

Acetabulum (Lat. _acetabulum_, a small vinegar-cup). The cup-shaped cavity of the innominate bone for receiving the head of the femur.

Acid (Lat. _acidus_, from _acere_, to be sour). A substance usually sour, sharp, or biting to the taste.

Acromion (Gr. ἀκρον the tip, and ᾧμος, the shoulder). The part of the scapula forming the tip of the shoulder.

Adam’s Apple. An angular projection of cartilage in the front of the neck. It may be particularly prominent in men.

Adductor (Lat. _adduco_, to draw to). A muscle which draws towards the middle line of the body, or of the hand or foot.

Adenoid (Gr. ἀδήν, a gland). Tissue resembling gland tissue.

Afferent (Lat. _ad_, to, and _fero_, to convey). Vessels or nerves carrying the contents or impulses from the periphery to the center.

Albumen, or Albumin (Lat. _albus_, white). An animal substance resembling the white of an egg.

Albuminuria. A combination of the words “albumin” and “urine.” Presence of _albumen_ in the _urine_.

Aliment (Lat. _alo_, to nourish). That which affords nourishment; food.

Alimentary (Lat. _alimentum_, food). Pertaining to _aliment_, or food.

Alimentary Canal (Lat. _alimentum_). The tube in which the food is digested or prepared for reception into the blood.

Alkali (Arabic _al kali_, the soda plant). A name given to certain substances, such as soda, potash, and the like, which have the power of combining with acids.

Alveolar (Lat. _alveolus_, a little hollow). Pertaining to the alveoli, the _cavities_ for the reception of the teeth.

Amœba (Gr. ἀμείβω, to change). A single-celled, protoplasmic organism, which is constantly changing its form by protrusions and withdrawals of its substance.

Amœboid. Like an _amœba_.

Ampulla (Lat. _ampulla_, a wine-flask). The dilated part of the semicircular canals of the internal ear.

Anabolism (Gr. ἀναβάλλω, to throw or build up). The process by means of which simpler elements are _built up_ into more complex.

Anæsthetics (Gr. ἀν, without, and αἰσθησία, feeling). Those medicinal agents which prevent the feeling of pain, such as chloroform, ether, laughing-gas, etc.

Anastomosis (Gr. ἀνά, by, and στόμα, a mouth). The intercommunication of vessels.

Anatomy (Gr. ἀνατέμνω, to cut up). The science which describes the structure of living things. The word literally means dissection.

Antiseptic (Lat. _anti_, against, and _sepsis_, poison). Opposing or counter-acting putrefaction.

Antrum (Lat. _antrum_, a cave). The cavity in the upper jaw.

Aorta (Gr. ἀορτή, from ἀείρο, to raise up). The great artery that _rises up_ from the left ventricle of the heart.

Aponeurosis (Gr. ἀπό, from, and νεῦρον, a nerve). A fibrous membranous expansion of a tendon; the nerves and tendons were formerly thought to be identical structures, both appearing as white cords.

Apoplexy (Gr. ἀποπληξία, a sudden stroke). The escape of blood from a ruptured blood-vessel into the substance of the brain.

Apparatus. A number of organs of various sizes and structures working together for some special object.

Appendages (Lat. _ad_ and _pendeo_, to hang from). Something connected with a part.

Aqueous Humor (Lat. _aqua_, water). The watery fluid occupying the space between the cornea and crystalline lens of the eye.

Arachnoid Membrane (Gr. ἀράχνη, a spider, and εἰδώς, like). The thin covering of the brain and spinal cord, between the dura mater and the pia mater.

Arbor Vitæ. Literally, “the tree of life”; a name given to the peculiar appearance presented by a section of the cerebellum.

Areolar (Lat. _areola_, a small space, dim. of _area_). A term applied to a connective tissue containing _small spaces_.

Artery (Gr. ἀήρ, air, and τερέω, to contain). A vessel by which blood is carried away from the heart. It was supposed by the ancients to contain only air, hence the name.

Articulation (Lat. _articulo_, to form a joint). The more or less movable union of bones, etc.; a joint.

Arytenoid Cartilages (Gr. ἀρύταινα, a ladle). Two small cartilages of the larynx, resembling the mouth of a pitcher.

Asphyxia (Gr. ἀ, without, and σφίξις, the pulse). Literally, “without pulse.” Condition caused by non-oxygenation of the blood.

Assimilation (Lat. _ad_, to, and _similis_, like). The conversion of food into living tissue.

Asthma (Gr. ἆσθμα, a gasping). Spasmodic affection of the bronchial tubes in which free respiration is interfered with, owing to their diminished caliber.

Astigmatism (Gr. ἀ, without, and στίγμα, a point). Irregular refraction of the eye, producing a blurred image.

Atrophy (Gr. ἀ, without, and τροφή, nourishment). Wasting of a part from lack of nutrition.

Auditory Nerve (Lat. _audio_, to hear). The special nerve of hearing.

Auricle (Lat. _auricula_, a little ear). A cavity of the heart.

Azygos (Gr. ἀ, without, and ζυγός, a yoke). Without fellow; not paired.

Bacteria (βακτήριον, a staff). A microscopic, vegetable organism; certain species are active agents in fermentation, while others appear to be the cause of infectious diseases.

Bactericide (_Bacterium_ and Lat. _caedere_, to kill). Same as _germicide_.

Bile. The gall, or peculiar secretion of the liver; a viscid, yellowish fluid, and very bitter to the taste.

Biology (Gr. βίος, life, and λόγος, discourse). The science which treats of living bodies.

Bladder (Saxon _bleddra_, a bladder, a goblet). A bag, or sac, serving as a receptacle of some secreted fluid, as the _gall bladder_, etc. The receptacle of the urine in man and other animals.

Bright’s Disease. A group of diseases of the kidney, first described by Dr. Bright, an English physician.

Bronchi (Gr. βρόγχος, windpipe). The first two divisions, or branches, of the trachea; one enters each lung.

Bronchial Tubes. The smaller branches of the trachea within the substance of the lungs terminating in the air cells.

Bronchitis. Inflammation of the larger bronchial tubes; a “cold” affecting the air passages.

Bunion. An enlargement and inflammation of the first joint of the great toe.

Bursa. A pouch; a membranous sac interposed between parts which are subject to movement, one on the other, to allow them to glide smoothly.

Callus (Lat. _calleo_, to be thick-skinned). Any excessive hardness of the skin caused by friction or pressure.

Canal (Lat. _canalis_, a canal). A tube or passage.

Capillary (Lat. _capillus_, hair). The smallest blood-vessels, so called because they are so minute.

Capsule (Lat. _capsula_, a little chest). A membranous bag enclosing a part.

Carbon Dioxid, often called _carbonic acid_. The gas which is present in the air breathed out from the lungs; a waste product of the animal kingdom and a food of the vegetable kingdom.

Cardiac (Gr. καρδία, the heart). The cardiac orifice of the stomach is the upper one, and is near the heart; hence its name.

Carnivorous (Lat. _caro_, flesh, and _voro_, to devour). Subsisting upon flesh.

Carron Oil. A mixture of equal parts of linseed oil and lime-water, so called because first used at the Carron Iron Works in Scotland.

Cartilage. A tough but flexible material forming a part of the joints, air passages, nostrils, ear; gristle, etc.

Caruncle (Lat. _caro_, flesh). The small, red, conical-shaped body at the inner angle of the eye, consisting of a cluster of follicles.

Casein (Lat. _caseus_, cheese). The albuminoid substance of milk; it forms the basis of cheese.

Catarrh. An inflammation of a mucous membrane, usually attended with an increased secretion of mucus. The word is often limited to _nasal_ catarrh.

Cauda Equina (Lat., horse’s tail). The collection of large nerves descending from the lower end of the spinal cord.

Cell (Lat. _cella_, a storeroom). The name of the tiny miscroscopic elements, which, with slender threads or fibers, make up most of the body; they were once believed to be little hollow chambers; hence the name.

Cement. The substance which forms the outer part of the fang of a tooth.

Cerebellum (dim. for _cerebrum_, the brain). The little brain, situated beneath the posterior third of the cerebrum.

Cerebrum. The brain proper, occupying the upper portion of the skull.

Ceruminous (Lat. _cerumen_, ear wax). A term applied to the glands secreting cerumen, or _ear wax_.

Chloral. A powerful drug and narcotic poison used to produce sleep.

Chloroform. A narcotic poison generally used by inhalation; of extensive use in surgical operations. It produces anæsthesia.

Chondrin (Gr. χονδρός, cartilage). A kind of gelatine obtained by boiling _cartilage_.

Chordæ Tendineæ. Tendinous cords.

Choroid (Gr. χορίον, skin, and εἶδος, form). The middle coat of the eyeball.

Chyle (Gr. χυλός, juice). The milk-like fluid formed by the digestion of fatty articles of food in the intestines.

Chyme (Gr. χυμός, juice). The pulpy liquid formed by digestion in the stomach.

Cilia (pl. of _cilium_, an eyelash). Minute hair-like processes found upon the cells of the air passages and other parts.

Ciliary Muscle. A small muscle of the eye which assists in accommodation.

Circumvallate (Lat. _circum_, around, and _vallum_, a rampart). Surrounded by a rampart, as are certain papillæ of the tongue.

Coagulation (Lat. _coagulo_, to curdle). Applied to the process by which the blood clots or solidifies.

Cochlea (Lat. _cochlea_, a snail shell). The spiral cavity of the internal ear.

Columnæ Carneæ. Fleshy projections in the ventricles of the heart.

Commissure (Lat. _con_, together, and _mitto_, _missum_, to put). A joining or uniting together.

Compress. A pad or bandage applied directly to an injury to compress it.

Concha (Gr. κόγχη, a mussel shell). The shell-shaped portion of the external ear.

Congestion (Lat. _con_, together, and _gero_, to bring). Abnormal gathering of blood in any part of the body.

Conjunctiva (Lat. _con_, together, and _jungo_, to join). A thin layer of mucous membrane which lines the eyelids and covers the front of the eyeball, thus joining the latter to the lids.

Connective Tissue. The network which connects the minute parts of most of the structures of the body.

Constipation (Lat. _con_, together, and _stipo_, to crowd close). Costiveness.

Consumption (Lat. _consumo_, to consume). A disease of the lungs, attended with fever and cough, and causing a decay of the bodily powers. The medical name is _phthisis_.

Contagion (Lat. _con_, with, and _tango_ or _tago_, to touch). The communication of disease by contact, or by the inhalation of the effluvia of a sick person.

Contractility (Lat. _con_, together, and _traho_, to draw). The property of a muscle which enables it to contract, or draw its extremities closer together.

Convolutions (Lat. _con_, together, and _volvo_, to roll). The tortuous foldings of the external surface of the brain.

Convulsion (Lat. _convello_, to pull together). A more or less violent agitation of the limbs or body.

Coördination. The manner in which several different organs of the body are brought into such relations with one another that their functions are performed in harmony.

Coracoid (Gr. κόραξ, a crow, εἶδος, form). Shaped like a crow’s beak.

Cornea (Lat. _cornu_, a horn). The transparent horn-like substance which covers a part of the front of the eyeball.

Coronary (Lat. _corona_, a crown). A term applied to vessels and nerves which encircle parts, as the _coronary_ arteries of the heart.

Coronoid (Gr. κορώνη, a crow). Like a crow’s beak; thus the _coronoid_ process of the ulna.

Cricoid (Gr. κρίκος, a ring, and εἶδος, form). A cartilage of the larynx resembling a seal ring in shape.

Crystalline Lens (Lat. _crystallum_, a crystal). One of the humors of the eye; a double-convex body situated in the front part of the eyeball.

Cumulative. A term applied to the violent action from drugs which supervenes after the taking of several doses with little or no effect.

Cuticle (Lat. dim. of _cutis_, the skin). Scarf skin; the epidermis.

Cutis (Gr. σκῦτος, a skin or hide). The true skin, also called the _dermis_.

Decussation (Lat. _decusso_, _decussatum_, to cross). The _crossing_ or running of one portion athwart another.

Degeneration (Lat. _degenerare_, to grow worse, to deteriorate). A change in the structure of any organ which makes it less fit to perform its duty.

Deglutition (Lat. _deglutire_, to swallow). The process of swallowing.

Deltoid. Having a triangular shape; resembling the Greek letter Δ (_delta_).

Dentine (Lat. _dens_, _dentis_, a tooth). The hard substance which forms the greater part of a tooth; ivory.

Deodorizer. An agent which corrects any foul or unwholesome odor.

Dextrin. A soluble substance obtained from starch.

Diabetes Mellitus (Gr. διά, through, βαίνω, to go, and μέλι, honey). Excessive flow of sugar-containing urine.

Diaphragm (Gr. διαφράσσω, to divide by a partition). A large, thin muscle which separates the cavity of the chest from the abdomen.

Diastole (Gr. διαστέλλω, to dilate). The _dilatation_ of the heart.

Dietetics. That part of medicine which relates to diet, or food.

Diffusion of Gases. The power of gases to become intimately mingled.

Diplöe (Gr. διπλόω, to double, to fold). The osseous tissue between the tables of the skull.

Dipsomania (Gr. δίψα, thirst, and μανία, madness). An insatiable desire for intoxicants.

Disinfectants. Agents used to destroy the germs or particles of living matter that are believed to be the causes of infection.

Dislocation (Lat. _dislocare_, to put out of place). An injury to a joint in which the bones are displaced or forced out of their sockets.

Dissection (Lat. _dis_, apart, and _seco_, to cut). The cutting up of an animal in order to learn its structure.

Distal (Lat. _dis_, apart, and _sto_, to stand). Away from the center.

Duct (Lat. _duco_, to lead). A narrow tube.

Duodenum (Lat. _duodeni_, twelve). The first division of the small intestines, about twelve fingers’ breadth long.

Dyspepsia (Gr. -δύς, ill, and πέπτειν, to digest). A condition of the alimentary canal in which it digests imperfectly. Indigestion.

Dyspnœa (Gr. δύς, difficult, and πνέω, to breathe). Difficult breathing.

Efferent (Lat. _effero_, to carry out). _Bearing_ or _carrying outwards_, as from the center to the periphery.

Effluvia (Lat. _effluo_, to flow out). Exhalations or vapors coming from the body, and from decaying animal or vegetable substances.

Element. One of the simplest parts of which anything consists.

Elimination (Lat. _e_, out of, and _limen, liminis_, a threshold). The act of _expelling_ waste matters. Signifies, literally, “to throw out of doors.”

Emetic (Gr. ἐμέω, to vomit). A medicine which causes vomiting.

Emulsion (Lat. _emulgere_, to milk). Oil in a finely divided state, suspended in water.

Enamel (Fr. _émail_). Dense material covering the crown of a tooth.

Endolymph (Gr. ἔνδον, within, and Lat. _lympha_, water). The fluid in the membranous labyrinth of the ear.

Endosmosis (Gr. ἔνδον, within, and ὠθέω, to push). The current from without _inwards_ when diffusion of fluids takes place through a membrane.

Epidemic (Gr. ἐπί, upon, and δέμος, the people). An extensively prevalent disease.

Epiglottis (Gr. ἐπί, upon, and γλόττις, the entrance to the windpipe). A leaf-shaped piece of cartilage which covers the top of the larynx during the act of swallowing.

Epilepsy (Gr. ἐπίληψις, a seizure). A nervous disease accompanied by fits in which consciousness is lost; the falling sickness.

Ether (Gr. αἰθήρ, the pure, upper air). A narcotic poison. Used as an anæsthetic in surgical operations.

Eustachian (from an Italian anatomist named Eustachi). The tube which leads from the throat to the middle ear, or tympanum.

Excretion (Lat. _excerno_, to separate). The separation from the blood of the waste matters of the body; also the materials excreted.

Exosmosis (Gr. ἔξω, without, and ᾀθέω, to push). The current from within _outwards_ when diffusion of fluids takes place through a membrane.

Expiration (Lat. _expiro_, to breathe out). The act of forcing air out of the lungs.

Extension (Lat. _ex_, out, and _tendo_, to stretch). The act of restoring a limb, etc., to its natural position after it has been flexed or bent; the opposite of _flexion_.

Fauces. The part of the mouth which opens into the pharynx.

Fenestra (Lat.). Literally, “a window.” Fenestra ovalis and fenestra rotunda, the oval and the round window; two apertures in the bone between the tympanic cavity and the labyrinth of the ear.

Ferment. That which causes fermentation, as yeast.

Fermentation (Lat. _fermentum_, boiling). The process of undergoing an effervescent change, as by the action of yeast; in a wider sense, the change of organized substances into new compounds by the action of a ferment. It differs in kind according to the nature of the ferment.

Fiber (Lat. _fibra_, a filament). One of the tiny threads of which many parts of the body are composed.

Fibrilla. A little fiber; one of the longitudinal threads into which a striped muscular fiber can be divided.

Fibrin (Lat. _fibra_, a fiber). An albuminoid substance contained in the flesh of animals, and also produced by the coagulation of blood.

Flexion (Lat. _flecto_, to bend). The act of bending a limb, etc.

Follicle (Lat. dim. of _follis_, a money bag). A little pouch or depression.

Fomentation (Lat. _foveo_, to keep warm). The application of any warm, medicinal substance to the body, by which the vessels are relaxed.

Foramen. A hole, or aperture.

Frontal Sinus. A blind or closed cavity in the bones of the skull just over the eyebrows.

Fumigation (Lat. _fumigo_, to perfume a place). The use of certain fumes to counteract contagious effluvia.

Function (Lat. _functio_, a doing). The special duty of any organ.

Ganglion (Gr. γάγγλιν, a knot). A knot-like swelling in a nerve; a smaller nerve center.

Gastric (Gr. γαστήρ, stomach). Pertaining to the stomach.

Gelatine (Lat. _gelo_, to congeal). An animal substance which dissolves in hot water and forms a jelly on cooling.

Germ (Lat. _germen_, a sprout, bud). Disease germ; a name applied to certain tiny bacterial organisms which have been demonstrated to be the cause of disease.

Germicide (_Germ_, and Lat. _caedere_, to kill). Any agent which has a destructive action upon living germs, especially _bacteria_.

Gland (Lat. _glans_, an acorn). An organ consisting of follicles and ducts, with numerous blood-vessels interwoven.

Glottis (Gr. γλόττα, the tongue). The narrow opening between the vocal cords.

Glucose. A kind of sugar found in fruits, also known as grape sugar.

Gluten. The glutinous albuminoid ingredient of cereals.

Glycogen. Literally, “producing glucose.” Animal starch found in liver, which may be changed into glucose.

Gram. Unit of metric system, 15.43 grains troy.

Groin. The lower part of the abdomen, just above each thigh.

Gustatory (Lat. _gusto_, _gustatum_, to taste). Belonging to the sense of _taste_.

Gymnastics (Gr. γυμνάξω, to exercise). The practice of athletic exercises.

Hæmoglobin (Gr. αἷμα, blood, and Lat. _globus_, a globe or globule). A complex substance which forms the principal coloring constituent of the red corpuscles of the blood.

Hemispheres (Gr. ἡμί, half, and σφαῖρα, a sphere). Half a sphere, the lateral halves of the cerebrum, or brain proper.