200 



THE FROG— THE PLATANA 



(b) The tibialis posticus, lying between the gastrocnemius and the tibio- 



fibula and running along the whole length of the tibio-fibula. 



(c) The tibialis anticus, on the outer side of the leg. 



(d) The extensor cruris, lying between the tibialis anticus and the tibio- 



fibula. 



3. Muscles of the Thigh (dorsal surface) : 



(a) The rectus anticus femoris, occupying the outer dorsal surface of the 



thigh, arising from the ilium in front of the acetabulum and covering 

 the vastus internus. 



(b) The vastus externus, occupying the median dorsal part of the thigh and 



arising from the posterior dorsal edge of the ilium. These two muscles 

 (a) and (b), along with the vastus internus of the ventral surface, join 

 together to form the triceps extensor cruris, the great extensor muscle 

 of the thigh, which is inserted into the tibia just below the head of 

 that bone. 



(c) The semimembranosus, a stout muscle occupying the inner surface of 



the thigh, and arising from the dorsal part of the ischium. It is 

 inserted into the back of the head of the tibia. 



(d) The biceps, a long slender muscle almost completely covered by the 



vastus externus and the semimembranosus. 



4. Muscles of the Shank (dorsal surface) : 



(a) The gastrocnemius. 



(b) The peroneus, a stout muscle occupying the outside of the leg between 



the tibialis anticus and the gastrocnemius. 

 \The muscles of the hind-limbs of the Platana are very similar to thosj of the 

 Frog, except that the rectus anticus femoris extends on to the ventro-lateral surface 

 of the thigh so as to cover almost the whole of the vastus internus. In the shank, the 

 tibialis posticus is much enlarged and covers the tibio-fibula completely.] 



Vastus externus Semimembranosus 



Gluteus 

 Rectus anticus femoris \ Biceps 



Triceps extensor {emoris 



Sea)imembranosus 

 Vastus externus ;' Rectus internus minor 



Gastrocnemius 



Rectus anticus femoris 



Per6neus 



Tibialis anticus 



Biceps 



Fig. 69. — A. Muscles of the Left Hind-limb of Rana ; and B. of Xeiwpus, from the 



dorsal surface. 



