Physiology Practicums: Explicit Directions for Examing Portions of the Cat ...

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Preface To The First Edition

^l u

About ten years ago, in the eflfort to enable the members of the general class in Physiology at Cornell University (150-180 in number) to study for themselves intelligently certain parts of the cat and sheep as an aid to the comprehension of the functions and relations of the corresponding human organs, I put alcoholic specimens before them and wrote on the blackboard brief directions which were orally amplified and illustrated. A few years later these directions were written upon cloth sheets that were suspended before the class. They were amplified and printed in the fall of 1889 and issued in their present form in 1892.

The separation of the sheets and plates has obvious inconveniences but upon the whole the practical advantages are greater.

From the first the assistants and students have cordially cooperated toward increasing accuracy and explicitness.

It is to be hoped that ere long as much as is here included may be required for admission to this and other universities, so that the instruction therein may commence upon a foundation both higher and more substantial than at present.

Ithaca^ N, K, December 26^ ^Sgj,

Preface To The Second Edition

I The text has been revised and largely rewritten. An eflfort has been

^ made to correct the errors and omissions detected during the three years'

tuse of the work at Cornell University and elsewhere. For helpful suggestions I am particularly indebted to my assistants. Dr. P. A. Fish and Dr. B. B. Stroud.

V: ^ The changes in the illustrations comprise new figures of the cat's

skeleton, and of the sheep's heart and brain. Two outlines have been introduced into the text.

The order has been modified so as to bring the examination of the head and neck just before that of the eye and brain. The eleven practicums are combined so as to form four Parts, each dealing with a natural group of subjects.

A teaching experience of twenty-seven years leads me to believe that explicitness should be a main feature of directions for beginners. To credit them with unlikely knowledge, judgment and skill, or with inspiration that will serve in place of those attributes, may compliment them and simplify the task of the writer. But there result perplexities, the formation of faulty methods, and the waste of time and material.

When, however, there has once been established a sound basis of fact and manipulation, the student may safely and profitably venture upon unfamiliar ground. He may either apply the directions to diflferent forms, or re-examine the same forms in diflferent ways. For example, the brain of the cat, dog, monkey or man may compared with that of the sheep, and the sheep's brain may be explored in ways other than that presented in the following pages.

September 20^ ^8^3-

Contents

PRACTICUM. SUBJECT. PAGES. PUATKS.

^1 I. The Cat : Its Form, Skeleton, Skin-Muscles, and Axillary

J^>-J Vessels and Nerves 5-8 I-IV

Part I. Practicum I : The Cat : Its Form And Certain Parts Of

ITS STRUCTURE.

PLATES REQUIRED : I — IV.

§1. Comparison of the Cat with Man, — At one of the earlier lectures of the course the cat's form, attitude and mode of progression, and the main features of its skeleton, were compared with those of man. Examine the mounted skeleton. Manipulate the specimen. Press upon the regions where bony prominences exist. Move the limbs as wholes and at their joints. Verify the statements made at the lecture and note additional points of resemblance and difference if possible.

a. The preserved specimen is less well-adapted for these topogra|>hic observations than the freshly-killed animal. Still more may be learned from the living cat, provided it and the observer are on such confidential terms as to permit unrestricted manipulation.

§2. The Leg, — Recognize the three joints, proximal, the hip, distal, the ankle, and intermediate, the knee, demarcating as many segments, viz^ the thigh with its single bone, femur ; the LEG proper (sometimes called crus) with its two bones tibia and fibula, and the FOOT (pes) composed of several small bones.

§ 3. One or both of the heels should retain a piece of the tendo Achillis^ seen on the right in Fig. i. Also at the knee should be retained the PATELLA or **knee-pan" (PI. I and Fig. i) a movable bone attached by a strong ligament to the head of the tibia, and giving insertion to the muscles on the **front" of the thigh.

§ 4. At the sides of the left patella cut carefully into the knee joint. Then cut transversely so as to separate the leg proper from the thigh. Note that the apposed ends of the femur and tibia present a bluish white covering of cartilage (gristle). This forms an elastic cushion like a buffer, to lessen the shock in moving and especially in alighting from a height.

a. Shave off a thin slice of cartilage ; hold it to the light and note its translucence.

b. In a freshly killed animal the interior of the joints would present a moist surface due to the synovia secreted by the lining membrane.

§ 5. Removing the Thigh, — a. Move the left thigh to and fro so as to indicate where its bone, the femur, joins the pelvis. On PI. I observe

I

6 Practicum I. The Joints and Ligaments.

the irregular form of the pelvis. Use the scissors to carefully cut away the muscles that have been left attached to the femur and pelvis.

a. After the flesh about the proximal end of the lemur is mostly removed, moving it will show that it has a head imbedded in a socket, and that there is a fibrous capsule extending from the margin of the socket over part of the head.

b. Push the femur as far as it will go in any direction ; this will render the capsule tense at the opposite side ; cut it here and continue till the head may be extracted slightly from the socket.

c. Note that its complete removal is prevented by a fibrous cord connecting it with the bottom of the socket ; this is the round ligament of the hip joint, present also in man and many animals but absent in the orang which uses its short leg freely as an arm. Cut the ligament.

§6. Compare the two ends of the femur. The subspherical head, on the constricted neck, enters into the composition of a * 'ball-and-socket joint;" the distal end forms at the knee a * 'hinge-joint." The patella (knee-pan) has been removed. The movements at either end are similar to those in man.

§ 7. The Periosteum, — Near the distal end of the bone note the covering of fibrous membrane, the periosteum. Divide it at any point, preferably with a pocket-knife or arthrotome. Insert the tracer between it and the bone ; strip it from the bone for a considerable area. Near the ends of the bone there may be seen vessels passing from it into the bone ; in the dried bone the small orifices for these vessels may be detected.

§ 8. The Marrow. — Transect the femur with saw, nippers or hatchet. The shaft of the bone forms a tube whose cavity is filled with a kind of fat, the MARROW. The ends are solid but of a spongy texture.

§9. Remove the right leg at the hip. Trim off remnants of flesh with the scissors and preserve for use at Pr. II.

§ 10. The Skin Muscles, — On PI. II, the irregular lines crossing between the words thorax and abdomen indicate the cut edge of a thin muscle the caudal part of which is supposed to have been removed with the skin ; the cephalic part narrows to be attached to certain muscles of the arm.

a. In the cat, as in most quadrupeds, in addition to the ordinary muscles of the limbs and those of the trunk which are attached to bones, there is a nearly continuous sheet of muscle in close relation with the skin ; this enables the horse, for instance, to shake off a fly, while the attachment to the arm increases the efficiency of that limb in ordinary locomotion or climbing. In man the skin muscles are present only on the neck and head, mainly as organs of expression.

§ II. At about the middle of the left side of the thorax, as indicated on Fig. I, make two incisions crossing one another at right angles and about 5 cm. (2 in.) long. Together they constitute a crucial incision,

a. These first incisions should divide only the skin, an apparently single, tough layer.

§ 12. There are thus established four triangular flaps of skin. With the forceps grasp the corner of one of these flaps, lift it and with the scalpel dissect it from the subjacent parts. Even if the incisions have divided more than the skin the latter may be isolated by taking care to lift only a single layer of tissue, the ental surface of which is white or dark, but not red or pink.

Practicum I. The Skin Muscles.

Fig. I. Diagram of a Cat as prepared for practicum purposes. The hair was removed by immersion in water at about So'' C. (,176'' F.). The skin and most of the flesh have been cut from the legs and hips, and the tail abbreviated. At the right heel is seen a part of the TENDO ACHILLIS, the large tendon by which the muscles of the **calf of the leg" were inserted. The special object of the figure is to indicate the crucial incision by means of which the skin muscle is to be exposed.

a. When the four flaps of skin have been lifted they may be cut off with the scissors. There will then be exposed a quadrangular area of the SKIN-MUSCLE, recognizable by its pale red color and from the sparseness of its fascicles (bundles of fibers). Even if it has been divided by the crucial incision it may be cut out as a thin sheet, separated b.y FAT and CONNECTIVE TISSUE from an ental, thicker muscle, the latissimus, whose fascicles run in nearly the same direction ; see PI. II, just dorsad of the word abdomen.

b. If the foregoing operations fail on the left side, repeat on the right with additional precautions.

c. On the neck, from a point about midway of its length and dorso-ventral diameter (on PI. II coinciding nearly with the dorsal end of the line between the E and the c of neck), cut caudad along the middle of the left side to the root of the tail, or to the cut margin of the skin in case it

j and the flesh have been removed from the hips and legs. This incision

I should divide both the skin and the skin-muscles. On the neck and

I shoulder no great harm would result from cutting too deeply, but on the

thorax care should be taken not to cut the latissimus, and on the abdomen there is danger of opening that cavity prematurely.

d. Grasp the cut edge of skin and skin-muscle, at the dorsal side of area exposed in (a), and dissect them up from the latissimus, remembering that the latter has a free margin extending obliquely toward the arm in continuation of the line shown in PI. II. On the neck and shoulders some irregularities and adhesions will be encountered, but no serious difficulties. In this way *^skin" the left side dorsad as far as the meson.

§ 13. Do the same for the ventral half of the left side, noting three features : (2) The mammary gland, a whitish, lobulated organ, quite large in nursing females, and extending the whole length of the abdomen and upon the thorax ; (2) the series of nipples connected therewith ; (3) the narrowing and thickening of the latissimus near the arm ; (4) the pectoral muscles, thicker and darker than the skin-muscles and having a direction from the meson latero-cephalad (PI. III).

8 Praciicum I. The Pectoral Muscles.

a. Taking care not to cut the pectorals, divide the skin and skin-muscles around the arm just proximad of the elbow. Do the same for the right arm and then, if necessary, for the legs, at about the middle of the thighs. Finally cut the skin just caudad of the ears.

b. If preferred the skin may now be divided with the scissors along both mesons (dorsal and ventral median lines) ; or it may be removed from the right side by dissecting it up from either or both mesons. The skin of the head should be left until that region is dissected.

c. Examine the ental aspect of the skin and note the pale sheet of skin-muscle, with close adhesions, especially caudad ; it narrows and thickens cephalad and is connected with muscles attached to the arm.

§ 14. Place the cat on its back and tie the arms outstretched to the loops at the side of the tray. Compare PI. III. Recognize the convex shoulders and the axillas (arm-pits).

The MESON (middle line) may not be perfectly straight on account of the twisting of the body. At the meson may be recognized the epigastrium (pit of the stomach), and the sternum (breast-bone) extending thence to the root of the neck PI. II, /.

§ 15. The Pectoral Muscles. — These form, as in man, a considerable mass covering the ventral aspect of the thorax and extending thence to the brachium. Read the description on PI. Ill, and note the differences from the human.

The cephalic margin of the pectoral mass overlaps the muscles on the ventral aspect of the neck ; it extends nearly transversely to the convexity of the shoulder. The cephalic margin is sometimes distinct, but sometimes quite thin and so closely adherent to the cervical muscles as to separate with some difficulty. The caudal margin is thinner and extends obliquely from the axilla to the epigastrium.

§ 16. Transecting the Pectorals. — Compare Plates III and IV.

a. At a point on the cephalic margin about (not more than) one-fourth of the distance from the meson to the convexity of the shoulder, begin an incision which is to be carried caudad parallel with the meson to the caudal margin ; it should be not more than 3 mm. (one-eighth inch) deep ; the division of the ectal layers will expose ental layers not quite parallel therewith.

A. Divide the ental layers by a second incision of about the same depth, so as to reach a muscle, the rectus, whose direction is parallel with the meson instead of at an angle with it.

c. Just ental of the pectorals are some nerves and blood-vessels which are not to be cut at this time.

§ 17. The Axillary Parts, — Lift the lateral portion of the pectoral mass and partly tear, partly cut it toward the arm. In the interval between it and the arm and the thorax may be seen :

a. Web-like connective tissue, composed of delicate fibers.

b. In well-nourished animals, masses of firm white FAT.

c. Several nerves, white and solid.

d. A smaller number of blood-vessels, elastic, hollow, and sometimes containing blood. The main artery usually lies a little cephalad of the vein (PI. 4), is more elastic and probably more nearly empty.

e. The axillary parts should be exposed with the tracer rather than the scalpel.

§ 18. The Clavicle (collar-bone).— Note its location on PI. I. Feel for it among the transected muscles at the shoulder ; it is usually laterad s

Practicum I. The Clavicle. 9

of the cut as in PI. IV. To expose it more fully evert the muscles, tearing the connective tissue. When the clavicle is found tear and cut it from the muscles. Scrape clean with a dull e6^e. Note the slight curvature of its ends in opposite directions, an'l that the lateral or scapular end is the wider.

a. In man and some other animals the clavicle is firmly connected with the sternum at one end and at the other with the scapula (shoulder-blade), and thus serves to brace the arm away from the trunk. In the cat the attachments are loose ; in the dog it is an insignificant ossicle ; in the horse, cow, sheep, etc., it is altogether absent.

d. The cleaned and dried clavicle of the cat is entirely inoffensive and may be preserved or even carried in the vest pocket as a good example of the organs which are apparently functionless and are hence called atelic,

§ 19. Transect the other pectorals and axillary parts Cut the cords that hold the arms to the tray. Turn the cat so that it rests on the ventrum. Note the wide muscle converginjj from the ribs to the vertebral margin of the scapula. Together these muscles support the trunk between the arms somewhat as would a broad sling.

§ 20. Divide these muscles and any other parts and detach the arms. Tie them and the right leg together with a tag bearing the name of the student, the number of his Practicum Section (I, II, III or IV) and the number of his seat (i, 2, 3 etc.).

4 •

PRACTICUM II. DISSECTION OF THE CAT'S ARM.

PIRATES RRQUIRBD : I, II, III, IV, V.

A ligamentous skeleton of the arm should be available for examina-^ tion if possible. If all are supplied contiguous students should have a right and a left. A leg was saved from Pr. I.

§ I. Review the Segments^ Joints and Larger Bones of the Arm from Plates I and II ; the scapula now appears to constitute a segment of the limb instead of a part of the trunk.

§ 2. Learn the Technical Names of the Five Digits { fingers) ; poi,- LEX (thumb); INDEX (forefinger); mkdius (middle-finger); annularis (ring-finger) ; minimus (little-finger). On PI. V all are visible and named excepting the minimus. The pollex is the shortest, its attachment is most proximal and in the cat it is not opposable to the other digits like the human thumb.

§ 3. Determine whether the Arm be Right or I^ft as follows : Hold it in front of you, the hand downward and the elbow toward you ; if the pollex is toward your right the arm is the left ; if toward your left the arm is the right.

§4. Determine the Aspects of the Arm. — That which bears the pollex is next the thorax, and is the 'inner" or ulnar; the other is the '*outer" or radial.

a. There is liability to some confusion here since the pollex is in line with the radius ; but in the cat the radius is crossed upon the ulna so as to rotate (pronate) the hand and bring the pollex upon the ulnar side.

b. The student may illustrate the two conditions upon his own arm as follows : If the hand be placed upon the table with the palm upward the pollex is ''outer" and the two bones of the antibrachium (ulna and radius) are parallel, the radius as a whole lying upon the ''outer" side. But if the palm be turned down the distal end of the radius crosses to the "inner" side of the ulna and the pollex likewise comes to be on the ulnar or "inner" side of the limb, as in the cat

§5. Remove the Skin from the Arm, — In Pract. I, §4, A, the skin was cut around the arm between the elbow and shoulder. It may be "stripped" to the wrist, everted as a closely-fitting glove-finger may be turned inside out. Cut it at or distad of the wrist. Its complete removal may require slitting along the dorsum of each digit.

§6. With the Scissors Trim off the ^w^^:/^^ remaining attached to the dorsal or vertebral border of the scapula. Since the dorsal border of the scapula is convex the concavity of the curved scissors should be applied to it. The ragged remnants of the skin-muscle attached to the latissmus should also be cut off.

§ 7. With young cats the border of the scapula consists of a strip of cartilage which later is converted into bone. With the arthrotome or a pocket-knife cut a notch' through the cartilage into the bone ; the former Snav^bfe broken from the latter along their line of junction.

Ppacticum II. The Shoulder Mtiscles. 11

§ 8. Note the Remnant of the Pectoral Mass mostly on the cephalic and **outer" aspect of the brachium ; on the caudal and '"inner" side is another mass consisting of the latissinius and the TERES, a shorter muscle extending from the caudal margin of the scapula to the humerus. If the latissrimus and teres be drawn entad from the brachium there will appear, passing from them to beyond the elbow a wide and strong fascia, almost a tendon ; between it and the brachium is connective tissue which may be cut or torn.

a. On the ental side of the shoulder, in a ragged mass between the pectoral and lalissimus are a nerve, a blood-vessel, and connective tissue. Into the space loosely filled by them crowd the thumb or a scalpel handle. The space will be found bounded by a musculo-fibrous arch.

9. Cut the Arch at its Highest Pointy between the pectoral and latissimus masses. Turn these in opposite directions. Note that they covered a fusiform, slender muscle, the biceps, PI. V, and that along its inner side, near the humerus, passes a nerve, the musculo-cutaneous ; see § 18.

% 10. On the Ectal Surface of the Scapula is a thin sheet of muscle and fascia attached to the bony ridge (spine) which projects from it. Cut along the line of this attachment and remove.

§ II. Removal of Other Muscles, — Keeping the biceps constantly in mind, the muscles about the shoulder may be removed as follows :

a. Transect the mass covering the ental aspect of the scapula at about the middle of its length, i, e,^ at the word muscle in PL V; after dividing the muscle with the scalpel use the arthrotome and cut down to the bone. Peel the proximal (dorsal) part of the muscle off, noting that :

1. The fibers diverge toward the vertebral border.

2. They arise not by ordinary tendons but directly from the periosteum. The periosteum may be lifted on the point of the scalpel.

b. On the lateral aspect is a bony ridge, the '*spine" of the scapula, shown but not named on PI. I. Avoiding that, the muscles at either side of it are to be transected at about one-third the way from the dorsal border. Note that they arise from the '*spine," as well as from the general surface of the scapula.

§12. Relation of the Muscles to the Shoulder Joint. — Cut between the distal portions of the three muscles along the margins of the scapula and peel them off to the shoulder. Their attachments cover the shoulder joint so as to lessen the liability to dislocation of the head of the humerus from the shallow glenoid cavity. Note that pulling upon them moves the arm in corresponding directions : also that various combinations of the three muscles enable the arm to be rotated in intermediate directions.

§ 13. The Capsule of the Shoulder. — Transect all the muscles at the head of the humerus so as to expose in some degree the fibrous capsule of the joint, comparable with what was seen at the hip ; Pract. I, § 5, b.

§ 14. The Triceps. — The '*elbow" side (dorsum) of the brachium presents a thick mass of mucles which may here be designated under the general name triceps.

§ 15. The Brachial Plexus. — On the ental side of the arm arc several white, thick, firm NERVES. These are part of the Brachial Plexus, Pr. I, § 17, c^ PL IV, and were cut in removing the arm.

§ 16. The Ulnar Nerve. — In the interval between the biceps and the triceps, on the ulnar (**inner'') side, search with the tracer for a large

12 Ppactiurfi II. The Biceps and Brachialis.

white cord, the ulnar nerve. Trace it to the elbow, where it is lodged in a notch between the projecting olecranon process (PI. I) and the ulnar projection of the humerus.

a. It has the same location in man and, notwithstanding the protection from injury thus afforded, an unguarded blow upon this part of the elbow may so far press upon the nerve as to cause the tingling and more or less painful sensation known as '*crazy-bone."

h. Slit the fascia of the antibrachium and separate the muscles so as to follow the nerve distad. At about the middle of the length of the antibrachium it divides into two branches of which one is distributed to the palm and the other to the dorsal skin of the hand ; branches are given off to the pad at the wrist joint.

§ 17. Division of the Triceps, — Transect it at about the middle ; turn the distal half away from the bone, leaving it attached for later observation. Cut the proximal half from the humerus and scapula.

§ 18. The Musculo- Cutaneous Nerve, — Between the biceps and the bone push first a scalpel-handle and then a finger ; then draw the muscle gently from the bone and rotate it slightly. This will expose a nerve, the musculo-cutaneous, which emerges from the parts about the shoulder, sends several branches to the proximal part of the biceps and then continues to the elbow, passes to the radial side of the arm, and is distributed to the skin ; Anatomical Technology^ Fig. 103, N. Mct,^ and § 1022.

a. Like many other nerves it supplies, both muscle and skin, containing fibers derived from both the ventral (motor or ^'anterior") and dorsal (sensory or **posterior") spinal nerve roots ; it is a **mixed" nerve; see Practicum VI, the myel.

§ 19. Origin of the Biceps, — The tapering proximal end of the muscle terminates in a single, subcylindrical tendon (sinew) which enters a groove in the bone covered by a fibrous sheet ; PI. V, j, 4, Slit the sheet and follow the tendon to its attachment on a slight projection of the lip of the glenoid cavity of the scapula.

a. The second tendon of origin in man from the tip of the coracoid process (whence the name biceps) is absent in the cat ; PI. V.

§ 20. The Brachialis. — Partly covered by the biceps and lying closely against the '*outer'' side of the humerus is the brachialis (*rflrrAiii//j anticus). The distal ends of the two muscles may be followed together as directed in § 21.

§21. Insertion of the Biceps, — This is hidden by muscles of the antibrachium arising from both sides of the humerus but especially from the radial ("outer'') side. These must be cutaway, though not necessarily so far distad as in PI. V. Transect the muscles of the antibrachium covering the insertion of the biceps at about one-third of the way from the elbow to the wrist, and peel the proximal portions toward the wrist, but without cutting them away at their origins.

a. The fibrous sheath, fascia, covering them receives a slip of tendon from the biceps. This really constitutes a second and considerable insertion of the muscle, so that, especially in the absence of the second head one might well regard this muscle in the cat as a bipes rather than a biceps,

§ 22. Insertion of the Brachialis, — Use the tracer as much as possible, the scalpel sparingly, and ascertain that the brachialis is inserted upon the ulna, while the tendon of the biceps passes between the ulna and the

Practieum II. Flexors and Extensors. 13

radius ; if the hand be supinated vigorously and as far as possible, the attachment may be seen.

a. Carry the scalpel along the humerus between it and the brachialis so as to detach the muscle except at its origin.

§ 23. Actions of Certain Muscles upon the Antibrachium, — The antibrachium is a LEVER divided at the elbow joint into a long arm, and a

SHORT ARM, the OLECRANON, PL I.

a With either of the muscles to be experimented with, biceps, triceps and brachialis, the natural contraction may be imitated sufficiently by pulling proximad in the line of its length ; the effect is the same as if the muscle shortened itself like a piece of rubber that has been stretched.

§ 24. Flexion. — Grasp the humerus, the elbow down. Pull upon the brachialis. The hand rises and the arm is flexed just as when, in life, the muscle contracts.

The antibrachium constitutes a flexion LEVER, the power (brachialis) being applied between the weight (hand) and the fulcrum (elbow joint).

§ 25. Extension. — Grasp the humerus, the elbow up. Pull upon the triceps. The arm is extended just as when, in life, the triceps contracts. The antibrachium now constitutes an extension lever, the fulcnim (elbow joint) being between the weight (hand) and the power (triceps).

§26. Rising. — Grasp the humerus, the elbow down, it and the hand resting upon the table. Pull upon the triceps so as to straighten the arm at the elbow.

a. The condition is the same as when, upon all-fours, we rest the hand and antibrachium upon the floor and then raise the body by straightening the arm at the elbow. The weight (brachium, etc.,") is between the fulcrum (contact of the hand with the floor) and the power (triceps).