272 



There are two muscles, ac- 

 cessory to this great caudal ex- 

 tensor in their action, which are 

 as follows : — 



12. II. extensori femoris caudali 



accessorius, . . O01 oz. 



Origin ; from the fascia co- 

 vering the great caudal 

 extensor, and hy a ten- 

 dinous head from the 

 quadratus femoris, which 

 is also an accessory to 

 the great caudal. 



Insertion ; into the looped 

 tendon of the semimem- 

 branosus, already de- 

 scribed . 



13. 31. quadratus femoris, 



0-05 oz. 



Origin; posterior, superior, 

 and inner surface of the 

 pubis, near its symphy- 

 sis. 



Insertion ; into the hack of 

 the femur, with the ac- 

 tion and position of the " 

 quadratics femoris in § 

 mammal quadrupeds, I" 

 and into the tendon of § 

 the great caudal exten- |- 

 sor. 



The effect of the interlacing 

 of the tendons of the various 

 muscles already described must - 0 * 

 be to produce simultaneity of & 

 action among them, such as I g 

 have already endeavoured to S 

 describe in my account of the 1 

 leg of the Ostrich ; and in the 8. 

 present instance of the Croco- g 

 dile there seems to be a similar ft 

 principle involved. The Croco- IT 

 dile, resting on mud, progresses 

 chiefly by using his hind feet as 

 paddles ; and in this use of 

 them the great caudal exten- 

 sor of the thigh is the most 



