Part 37

The sense of taste is located in the mouth-cavity, especially in the mucosa of the tongue and the soft palate. The proper organs of taste are the so-called taste-buds, found on the papillæ of the tongue, the soft palate, etc. Their exact distribution in the cat has apparently not been worked out.

V. THE INTEGUMENT. INTEGUMENTUM COMMUNE.

The skin of the cat consists of the usual two layers, the outer =epidermis= and the inner fibrous =corium=. The skin is particularly thick and tough about the sides of the neck and face.

The skin is covered almost completely with fine soft hairs. Only the end of the nose, the pads on the soles of the feet, and the nipples are without hair. A number of long stiff sensory hairs (vibrissæ) are found on the upper lip, the cheek, and above the upper eyelid.

The pads on the soles of the feet are cushion-like projections of skin, composed largely of connective and elastic tissue and fat. There is one large pad for each foot, and in addition a small pad for each digit. The fore limb has besides a small conical pad which is situated almost exactly over the pisiform bone.

The =nails= are horny outgrowths of the epidermis, covering the distal phalanges.

The =muscles= of the skin are the cutaneus maximus and platysma; these have been described (page 93). The superficial facial muscles are differentiations of the skin-muscles.

APPENDIX.

PRACTICAL DIRECTIONS.

The following appendix on the dissection and study of the cat is not intended as a general treatise on methods of preservation and dissection, but attempts only to give the application of well-known methods to the dissection and study of the particular animal with which the book deals. General methods which are referred to but not described must be looked up, if unfamiliar, in the manuals of general methods.

_Aids to Dissection and Study of the Cat._--A copy of Jayne’s “Mammalian Anatomy” should be in the laboratory for reference. Only the volume on the Bones of the Cat has been issued thus far.

Wilder and Gage’s “Anatomical Technology” will be found very useful for methods of work.

The plates of Strauss-Durckheim’s “Anatomie du Chat” are exceedingly valuable for the bones and muscles, and should be in the laboratory if possible. Outline reproductions of these plates have been published by H. S. Williams (G. P. Putnam’s Sons, New York, 1875). The use of both the original plates and the reproductions is made difficult by the antiquated nomenclature used for the structures figured.

_Method of Use of the Present Directions._--Except in the case of the Bones, the order of study of the structures is usually not the same as the order in which they are described. This is of course due to practical difficulties in dissection. The present directions give the _order of study_, or at least the order of dissection; of course after dissection the structures can be reviewed in the logical order given in the descriptions. But in the first study and dissection, the student is to use these directions for the _order of work_, while using the body of the book for the descriptions. It will be necessary therefore to keep the book opened in two places,--one in the appendix, for the directions; one in the body of the book, for descriptions. In studying the muscles, for example, the student will follow the order of dissection given in the appendix, but as every muscle is dissected he will find, confirm, and study the description of that muscle given in the body of the book. Other organs are studied in a similar manner.

Before commencing the study, read that portion of the preface which explains the use of _terms of direction_ (page VII).

Note that the page on which any figure is found may be determined by consulting the list of figures given in the Table of Contents.

THE BONES.

The bones will of course be studied from dried specimens. These may be prepared once for all and kept in the laboratory from year to year. A number of mounted skeletons of the cat should be at hand; these must be prepared by some one who has skill in such work.

_Preparation of Separate Bones._--For preparing the separate bones the liquid-soap process recommended by Wilder and Gage (“Anatomical Technology,” p. 107) will be found most convenient. This is as follows: The skin and soft parts are removed as far as possible without injury to the bones.

Make the following “liquid-soap” mixture:

Soft water 2000 cc. Strong ammonia 150 cc. Nitrate of potash (saltpetre) 12 grams. Hard soap 75 grams.

Heat these together till a homogeneous mixture is formed. Now immerse the bone or bones to be cleaned in a liquid composed of four parts water to one part of the above liquid-soap mixture. Boil forty minutes; pour off the liquid and renew it. Boil about half an hour longer; then remove soft parts with fingers, scalpel, and brush. The bones may be boiled as much longer in the mixture as is necessary to make the soft parts come away easily. If they are boiled too long, however, the epiphyses will separate from the bones. This is especially likely to occur in young skeletons, which must therefore not be boiled so long as the bones of an old cat.

Skeletons prepared in the following rough way are useful for many purposes. The entire body of the cat, or a single limb, is placed in the liquid-soap mixture (after partial removal of soft parts), and boiled till the muscles may be removed, but the ligaments, holding the bones together, remain. Clean thoroughly without removing the ligaments, and allow to dry. The bones are thus held together in their natural positions. Skeletons so prepared are not elegant, but are frequently useful.

_Disarticulation of Skulls._--The bones of the skull may be separated as follows: Clean the skull in the liquid-soap mixture, as above described. Then fill the cranial cavity with dry rice, beans, corn, or some other seeds that swell much on imbibition of water. Cork up the foramen magnum, and place the skull for twelve to twenty-four hours in water. The swelling of the grain will partially separate the bones at the sutures. The bones may then usually be separated completely by hand.

Entire skulls, and longitudinal sections, as represented in Fig. 43, p. 60, should be at hand.

_Study of the Bones._--The bones should be studied in the order in which they are described. No further special directions for their study are necessary.

_Study of Ligaments._--It will usually not be practicable for each student to make the dissections and preparations necessary for studying the ligaments. Rather should these be examined on demonstration preparations preserved in the laboratory. Such preparations may most easily be made by using _fresh_ material, and dissecting away muscles and other tissues, leaving only the ligaments connecting the bones. The preparations are then preserved in one or two per cent. formalin. It is difficult to prepare the ligaments satisfactorily on preserved material, because they do not stand out clearly from other tissues in such material, so that they are not easily distinguishable.

MUSCLES.

_Preparation and Preservation of Material._--Formalin forms by far the most satisfactory preservative for anatomical material. It is much better in almost every respect than alcohol, and has the additional advantage of being much cheaper.

After injecting with formalin, the cat may be preserved either immersed in a weaker solution of the same substance, or may be kept for a long time simply wrapped in a cloth dampened with formalin. The details of preparation differ according to which method is to be used.

In either case, the cat should be killed with chloroform, by placing it in a tight jar or box with a cloth or bit of cotton saturated with chloroform. It is not necessary to bleed the specimen. When the cat is dead, remove it to a tray, place it on its back, and tie the limbs loosely so that they will remain outspread.

Expose the femoral artery in the thigh, as follows: Make a median longitudinal incision through the skin of the abdomen, from a point an inch or two caudad of the xiphoid process to the pubis. Make an incision passing from near the middle of this obliquely laterad onto the thigh, for about three inches. Reflect the two flaps in the angles between these cuts, then with forceps and tracer isolate the femoral artery just as it passes into the thigh (Fig. 127, _a_). Make with scissors an oblique incision in one side of the artery, one-half to one inch from the point where it leaves the abdominal cavity. Introduce a canula directed toward the body, and tie it in place.

1. If the cat is to be preserved immersed in a solution of formalin, it should now be injected with a five per cent. solution of commercial formalin in ordinary water (commercial formalin 5 parts; water 95 parts). Into an adult cat 300 to 400 cubic centimeters of the five per cent. formalin should be injected.

The cat may now be preserved in a one per cent. solution of formalin. Before immersing it in the formalin it is well to remove the hair in some way, otherwise this will hold much water and be very inconvenient in dissection. The neatest method is to cut off the hair with scissors; this takes some time, however. If the skin-muscles (p. 93) are not to be dissected, the skin may be removed. It is well in this case to leave the skin on the sides of the head and on the feet.

It is not necessary to open the abdominal cavity, after injecting with the five per cent. formalin. If there is at any time reason to suspect that the viscera are not keeping well, the abdominal and thoracic cavities should be filled with five per cent. formalin by making a small hole through the body wall into the cavity, introducing a canula, and injecting till the cavity is full.

The specimen should be kept in a jar or other vessel and should be completely immersed beneath the one per cent. formalin. Any parts projecting above the fluid may be attacked by mould. If a part is found to be moulded, it should be submerged, when the mould will be killed. The mould injures the specimen if allowed to grow for a long time, but if discovered soon, no very serious harm results.

During dissection, exposed parts of the body should be kept from drying by covering with a damp cloth. Specimens preserved in formalin dry out much less quickly than those preserved in alcohol.

2. For some purposes it is much more convenient to preserve the material without immersing it in a vessel of formalin. Specimens injected with five per cent. formalin, as above directed, would usually keep perfectly without further treatment, but for two difficulties: (1) the specimen may _dry_; (2) it may be attacked by mould.

The drying may be prevented as follows: Use for injecting a mixture of the five per cent. formalin with one-sixth its volume of glycerine. This will dry only very slowly, and if pains are taken to keep exposed parts covered with cloths dampened with the mixture of formalin and glycerine, there will be no trouble from this source. The skin should not be removed from such specimens except as necessary in the course of dissection. The hair will give little trouble, because dry.

The specimens should be kept in a tight box, that the fluid may not evaporate rapidly from the cloths used for wrapping.

The attacks of the mould present a difficulty not so easily overcome. As long as the specimens are in daily use for dissection, and exposed parts kept covered with cloths saturated with the glycerine and formalin mixture, little or no trouble is to be anticipated. But if the specimens are left untouched for some days, and particularly if exposed surfaces are not kept covered in the manner above recommended, mould is almost sure to attack them. Material neglected for a week may thus be ruined.

If mould is found at any time to be attacking the material, the attacked part should be cleaned and well wrapped in cloths saturated in the formalin-glycerine mixture. If such means are unavailing, the specimen should be immersed in a vessel of one per cent. formalin and preserved for the future in this. Recourse should be had at once also to this method of preservation if the specimen shows signs of decomposition by having a strong odor.

It seems probable that the attacks of the mould might be prevented by mixing some fungicide with the injecting fluid; experiments should be made in this direction.

There are many advantages in preserving the material if possible without immersing it. All parts retain their color and pliability much more completely, so that the different structures are much more easily distinguishable. The method above described, by the use of formalin and glycerine, is to be recommended when the material is to be worked on every day or so and is not to be kept longer than a few weeks. It is usually not very satisfactory in warm weather, however. If some method can be devised of entirely preventing the attacks of the mould, this will be an excellent method of preserving anatomical material.

The same specimens used for the study of the muscles will serve also for the spinal cord and brain if prepared by one of the methods above described. (For the viscera, blood-vessels, and nerves, other specimens will have to be prepared; for these, directions are given later.)

_Muscles to be Dissected._--It will probably usually be impossible in a given course of study to dissect all the muscles of the cat. The instructor will of course select such as seem most advisable to him. The following may perhaps be recommended as a good selection for a fairly extensive course: Muscles of the Fore Limbs (pp. 436-439); Muscles of the Neck and the Deep Muscles of the Head (pp. 439-441); Muscles of the Wall of the Thorax and of the Abdomen (pp. 441-442); Muscles on the Ventral Side of the Neck (p. 442). If the superficial facial muscles (excluding those of the ear) can be studied from a preparation, this will be a valuable addition to a course (pp. 434-435).

DISSECTION OF MUSCLES.

_General._--In dissecting muscles a prime requisite of successful dissection is to keep the muscles _clean_. Fat, connective tissue, etc., is to be carefully but thoroughly cleared away from the surface of muscles and from between them. Frequently when it seems impossible to distinguish the structures described, all difficulty will vanish as soon as the dissection is thoroughly cleaned.

In transecting a muscle, work under it completely from one edge to the other (except in case of very wide muscles), then introduce the scissors or scalpel, and cut it by a smooth clean cut. Always leave the entire origin with one-half of the muscle, the entire insertion with the other half.

The student must be prepared to find in some cases considerable variations from the conditions described. The descriptions attempt to give an account of the _usual_ structures, but specimens showing no variations whatever are undoubtedly rare.

DIRECTIONS FOR DISSECTING THE MUSCLES OF THE CAT.

I. THE SKIN-MUSCLES (pp. 93-96, and Fig. 62).

These will perhaps not usually be dissected. If they are to be dissected, proceed as follows: Make a ventral median longitudinal incision of the skin from the cranial end of the manubrium to a point opposite the crest of the ilium. Connect the cranial end of this incision with the middle of the lambdoidal ridge by a similar incision through the skin. Make another incision from the manubrium to the spinous process of the thirteenth thoracic vertebra. Connect the caudal end of the first incision by an oblique cut with the root of the tail. Make another incision from the convexity of the knee-joint along the fold of skin which connects the hind limb and body, as far as the incision which leads to the root of the tail. Make an incision surrounding the base of the forelimb. Now reflect these flaps one at a time, working in general from the ventral side toward the dorsal middle line. Take great pains not to take up the thin skin-muscle with the skin. In this way all of one side of the body will be uncovered. The cutaneus maximus (Fig. 62, _b_) and a part of the platysma (Fig. 62, _a_) will be thus exposed. Read and verify the descriptions of these muscles (pp. 93-96). The cranial portion of the platysma cannot be seen at this stage, but should be dissected in connection with the muscles of the face.

II. SUPERFICIAL MUSCLES OF THE FACE AND HEAD (pp. 96-107, and Figs. 63 and 64).

These will perhaps not usually be dissected by the student. They should be studied on a well-dissected laboratory preparation, if possible. If they are to be dissected, this should be done if possible on a fresh specimen, as it is very difficult to dissect them on preserved material. Proceed as follows:

The skin should be removed with care from the sides and top of the face and head, without injury to the external ear.

1. The platysma (p. 95, and Fig. 62, _a_). Determine its cranial attachments.

2. The intermedius scutulorum (p. 96, and Fig. 63, _a_).

3. The corrugator supercilii medialis (Fig. 63, _b_).

4. The orbicularis oculi (Fig. 63, _c_; Fig. 64, _s_).

5. The corrugator supercilii lateralis (Fig. 64, _k_).

6. Notice the frontoauricularis if it exists.

7. The levator auris longus (Fig. 63, _g_, _g′_). Transect and reflect.

8. The auricularis superior (Fig. 63, _k_). Transect.

9. The abductor auris longus (Fig. 63, _m_). Transect.

10. The abductor auris brevis (Fig. 63, _l_). Transect.

11. The epicranius (Fig. 63, _h_, _h′_). In dissecting this muscle the intermedius scutulorum and corrugator supercilii medialis may be cut by an incision parallel to the middle line but a short distance to one side of it.

12. The zygomaticus (Fig. 64, _d_). This and the two following muscles may usually be best seen running beneath the fibres of the platysma, without reflecting the latter. If necessary, however, the platysma may be transected and reflected, though this can be done only with great difficulty.

13. The submentalis (Fig. 64, _c_).

14. The depressor conchæ (Fig. 64, _b_).

The zygomaticus, submentalis, and depressor conchæ should now be transected one or two centimeters from the external ear. The corrugatores supercilii lateralis and medialis may be cut across between the eye and the ear, and reflected. There is thus exposed:

15. The frontoscutularis. Transect near the scutiform cartilage.

16. The adductor auris inferior (Fig. 64, _o_). Transect near its insertion.

The external ear is now attached to the head only by the external auditory meatus and the tragicus lateralis muscle. Read the description of the latter (p. 418, and Fig. 67, _a_), find it beneath the fat which surrounds the proximal portion of the external ear, and cut it as far ventrad as possible. Now cut across the cartilaginous auditory meatus as near to the tympanic bone as possible, and remove the external ear, preserving it for future study. (The remainder of the muscles of the external ear may be studied in connection with the study of the auditory organ.)

17. The orbicularis oris (p. 105 and Fig. 64, _i_).

18. The zygomaticus minor, if it exists (p. 105, and Fig. 64, _e_).

19. The quadratus labii superioris (p. 105).

_a._ The levator labii superioris proprius (Fig. 64, _f_).

_b._ The levator labii superioris alæque nasi (Fig. 64, _g_).

20. The caninus (p. 106, and Fig. 64, _f′_).

21. The buccinator (p. 106).

22. The myrtiformis (p. 106, and Fig. 64, _h_).

23. The “moustachier” (p. 107).

24. The quadratus labii inferioris (p. 107).

III. MUSCLES OF THE FORE LIMB.

A. _Muscles connecting the Arm with the Body._--If the skin-muscles have been dissected, as above, cut the cutaneus maximus near its insertion, and reflect it toward the median dorsal line; in this way remove it completely. Remove the platysma in the same way. The first layer of body-muscles is thus exposed.

If the skin-muscles are not to be dissected, these may be removed with the skin. If the skin has not yet been removed, proceed as follows:

Beginning at the cranial end of the manubrium make two incisions in the skin, one passing to the lambdoidal ridge and the other to the spinous process of the thirteenth thoracic vertebra. Raise the triangular flap thus formed, taking up the skin-muscles with it.

1. The trapezius group of muscles (pp. 115-117, and Fig. 68, _d_, _h_, and _j_) is now exposed and may be dissected. Begin with the spinotrapezius (Fig. 68, _j_). Read the description of the muscle, then raise its caudal border and work under it until its cranial border is reached and the middle of its inner surface is free. Then transect it, and reflect the two halves of the muscle toward the origin and insertion, clearing the fat, etc., from the inner surface of the muscle and the parts covered by it. Determine origin and insertion.

2. The acromiotrapezius (Fig. 68, _h_). Dissect in the same manner, being careful not to injure the broad thin tendon which connects the two muscles across the middle line.

3. The clavotrapezius (Fig. 68, _d_). Separate it carefully, from the cleidomastoid (p. 120). Transect and reflect, as before.

4. The occipitoscapularis (Fig. 73, _a_, p. 149). Note the strong fascia which separates it from the deeper muscles of the neck. Be careful not to injure adjacent muscles in tracing this toward origin and insertion. Transect.

5. The rhomboideus. Transect.

Recognize the levator scapulæ ventralis (Fig. 68, _f_), the sternomastoid (Fig. 68, _c_; Fig. 65, _g_), and the cleidomastoid (Fig. 65, _h_). Then dissect--

6. The levator scapulæ ventralis (Fig. 68, _f_). Its origin (Fig. 72, _c_, _c′_) cannot be seen at this stage and should be left until the cervical muscles are dissected. Be careful in transecting this muscle to separate it well from the cleidomastoid. Transect.

7. The cleidomastoid (Fig. 65, _h_). Its origin cannot be fully seen at this stage. Transect.

Make a midventral incision of the skin from the cranial end of the manubrium to a point opposite the crest of the ilium. From the caudal end of this incision make an incision to the root of the tail. From the cranial end of the incision in the ventral middle line make a cut around the base of the fore limb on its caudal side, thus connecting the ventral incision with the incision which passes between the manubrium and the thirteenth thoracic vertebra.

Make another incision from the convexity of the knee at the joint along the fold of the skin which connects the hind limb and body, to the incision which leads to the root of the tail.

Reflect the flaps thus formed so as to expose the body and flank, removing the skin-muscle with the skin.

8. The latissimus dorsi (p. 121, and Fig. 68, _m_). Dissect it up and transect it. Work carefully toward its insertion and note the origin from its outer surface in the axilla of a part of the cutaneus maximus, and at about the same place of a thin muscle, the epitrochlearis (p. 164, and Fig. 65, _r_), _without_ determining the insertion of the latissimus.

9. Dissect the pectoralis group of muscles (Fig. 65, and p. 144), i.e., the pectoantibrachialis (Fig. 65, _m_), the pectoralis major (_l_), pectoralis minor (_o_), and xiphihumeralis (_p_).

Determine the border of each muscle before lifting it, then work it up at its middle, transect it, and work toward its ends, determining origin and insertion.

Refer constantly to the skeleton.