A Practical Physiology: A Text-Book for Higher Schools

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.

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 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.

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.