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.