THE MUSCLES. 79 
communis digitorum muscle signifies by its name that it is 
the common extensor of the digits. 
DISSECTION OF THE MUSCLES. 
Since the other systems are of more importance from the 
standpoint of comparative anatomy and physiology than the 
muscular, only the more important muscles will be described. 
Great care should be exercised in removing the skin of the 
cat, in order that such superficial muscles as the platysma 
myoides on the neck and side of the face, and occipito- 
frontalis, may not be cut away. The skin is attached to 
the underlying muscles by the superficial fascia, a fibrous 
areolar tissue, which contains the subcutaneous fat more or 
less abundant in all specimens. The deep fascia is the 
fibrous and membranous layer of dense tissue lying close 
against the muscles and dipping down between them. The 
stronger parts of this fascia are called aponcuroses. 
Directions for Dissection.—Dissection does not mean 
the cutting up, but the intelligent separation of one organ 
from another and the removing of known portions to study 
the deeper structures more carefully, The muscles should 
not be cut loose from their origin or insertion, but merely 
separated from each other by cutting the deep fascia in 
the longitudinal direction of the muscle. If it is neces- 
sary to remove a muscle for displaying those beneath, it 
should be cut transversely in the middle and the two parts 
reflected. No portion of a muscle or other tissue should be 
removed without knowing what it is and noticing carefully 
its relation to the surrounding parts. The specimen under 
dissection should be securely nailed to the tray so that the 
muscles are made tense. When the parts become dry, they 
should be thoroughly wet with water. If the formalin in 
which the specimen has been preserved is irritating to the 
mucous membrane of the dissector, a half liter of 5% 
ammonium hydrate should be poured over the specimen. 
