210 VERTEBRATE ZOOLOGY 



Observe the position of the fore and hind legs with reference 

 to the trunk and to each other. The elbow and the knee will 

 be seen to project in opposite directions, the elbow being directed 

 backward and the knee forward. The primitive positions of the 

 vertebrate leg, as illustrated in some of the lower amphibians, have 

 already been spoken of (see page 65). In most of the land verte- 

 brates a further important change in the position of the limbs 

 takes place, which consists in the rotation of the whole limb 

 about 90 degrees. The fore limb rotates backward and the hind 

 limb forward, so that the elbow and the knee come to point toward 

 each other instead of in the same direction. 



In the hind limb the preaxial, or anterior, side, on which is the 

 big toe, is turned inward toward the body by this movement, and 

 the foot comes to be directed forward. 



The fore limb, in the cat and in most other mammals, under- 

 goes a further change. By the rotation just mentioned, the pre- 

 axial side of it, with the thumb, would be turned outward, away 

 from the body ; and the fore foot, as well as the proximal division 

 of the leg, would be directed backward. The lower end of the pre- 

 axial side, however, rotates again around to the inner side of the 

 leg ; so that in its final position it is on the side toward the body, 

 and the foot is directed forward. 



It is in this way that the big toe and the thumb both come to 

 be on the side of the leg toward the body, and both feet to be 

 directed forward, notwithstanding the fact that the knee and the 

 elbow point in opposite directions. 



Exercise 1. Draw an outline of a side view of the cat, and label the 

 various parts of the body. 



Exercise 2. Draw a dorsal view of the head. 



Exercise 3. Draw a front view of the head, showing the nostrils and 

 mouth. 



Exercise 4. Draw a semidiagrammatic sketch of the inner surface 

 of the fore foot and the hind foot, showing the toes, claws, and 

 walking-pads. Label all. 



The Internal Organs. Place the animal on its back on a dis- 

 secting board and fasten each foot firmly to the board by means 



