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ANIMAL MECHANICS. 



Muscles of Flexion. 



1. Rectus femoris. 



2. Sartorius. 



3. Iliacus. 



4. Psoas, 



Muscles of Extension. 



1. Biceps femoris. 



2. Semitendinosus. 



3. Semimembranosus 



4. Gracilis. 



5. Quadratus femoris. 



Muscles of Adduction. 



1. Adductor primus, . ". \ 



2. Adductor secundus («), . > (Ad. magnus.) 



3. Adductor secundus (j3\ . / 



4. Adductor tertius, . . (Ad. brevis.) 



5. Adductor quartus, . . (Ad. longus.) 



6. Adductor quintus, . . (Pectinseus.) 



7. Obturator extemus. 



These muscles are not all present together in any animal, 

 but the greater number of them are to be found in all ani- 

 mals, and their constancy of occurrence and similarity of ac- 

 tion have justly attracted the attention of anatomists, and 

 several theories have been proposed to explain their simila- 

 rity, among which the most remarkable is the theory which 

 accounts for this similarity by the hypothesis of the descent 

 of the several animals from a supposed common ancestor. 



I shall choose the Lion as the animal, in the case of which 

 I shall attempt to find the position of the socket of the hip 



