428 



CLASS REPTILIA. 



The thigh of the frog is rounded like that of man. The 

 muscles of the leg are strongly marked. They exhibit some 

 peculiarities. Among others, the triceps femoralis is formed 

 only of two very distinct portions. The anterior rectus is 

 wanting. The triceps cruvis has but one belly. It comes 

 from the interior under part of the ilium, and descends in 

 front and externally. 



The semi-tendinosus is formed of two bellies, one of which 

 is attached to the symphysis of the pubis, and the other to 

 that of the ischium. 



The semi-aponeurosis is the same as in man. The sar- 

 torius is couched directly in front of the thigh, and is not 

 contorted. There is no popliteus. 



The gastrocnemius has but one belly ; but it is inserted 

 by a little isolated tendon to the external edge of the crest of 

 the tibia, or, more properly speaking, of the bone which fol- 

 lows the femur. Its terminating tendon spreads under the 

 foot to form the aponeurosis plantse. 



The general sensibility of the frogs appears to be toler- 

 ably obtuse. They are killed with difficulty, even by the 

 severest wounds. The heart and entrails may be plucked 

 out without destroying them immediately ; but their power of 

 apparent organic contractility is very great. The heart con- 

 tracts and dilates a long time after the death of the animal, 

 and even when it has been extracted from the body, and se- 

 parated from the other organs. 



The bones of the nose and the intermaxillaries are very 

 short, and, being broader than they are long, give a round- 

 ness to the face of the frog. The cavity of the cranium is 

 very narrow, and the encephalon of very small volume. The 

 cerebral hemispheres are elongated and narrow ; the optic 

 beds are large and hollowed with a very marked ventricle. 

 Their volume exceeds that of the cerebral hemispheres. There 

 is no pons Varolii. 



