ANIMAL MECHANICS. 



389 



Muscles of Extension. 



Muscles of Extension. 



1. Biceps coracoradialis, . 



2. Biceps glenoideus, . . 



3. Brachiseus, 



4. Coracobrachialis capsularis, 



Biceps femoris. 

 Semitendinosus. 

 Semimembranosus. 

 Quadratus femoris. 



Muscles of Adduction. 



Muscles of Adduction. 



1. Coracobrachialis, .... Adductor primus. 



f Adductor secundus. 



Adductor tertius. 



2. Pectoralis major, . . . . <{ , 



Adductor quartus. 



I Adductor quintus. 



3. Pectoralis minor, .... Obturator externus. 



4. Pectoralis quartus, .... Gracilis. 



The similarity in the muscles of the shoulder and hip 

 is a necessary consequence of the idea which is common to 

 both joints ; viz., a single long bone revolving round a centre, 

 and acted on by muscles terminating in that bone, and taking 

 their origin from a girdle, either absolutely or relatively at 

 rest. There are some twenty or twenty-five actions necessary 

 in such a system, and, therefore, a muscle is " told off" to 

 perform to maximum advantage each proper action. In the 

 order of nature, the following method is observed in all the 

 mechanisms of the body, of every animal : — 



i°. A contriving Mind. 



2°. The Idea of the mechanism and its actions. 



3 0 . A perfect muscle to perform each action. 



4 0 . Bones of form, magnitude, and position, which can be 

 predicted from the condition of maximum work imposed on 

 each muscle employed. 



Here we obtain a solid and permanent foundation for the 

 Science of Comparative Osteology, founded on Geometry and 



