482 University of California Puhlicatians in Zoology [Vol. 13 



10 Omohyoideus 



lie Pectoralis tertius 



12 Subclavlus 



13 Serratus anterior 



The remainder of the muscles of the anterior limb may be 

 divided into two main classes: (A) muscles from the body to the 

 humerus (group 2), and (B) muscles of the arm proper (groups 3 

 to 8, inclusive). In considering the latter class, the muscles of the 

 arm, it is convenient to think of the arm as consisting of three 

 parts, the upper arm, the forearm, and the hand. Each of these 

 parts has a system of extensor muscles, or those which tend to 

 straighten it with relation to the bone situated next proximad, and 

 a system of flexor muscles, or those which tend to flex the given 

 part in relation to the bone next above it. It is of course obvious 

 that the extensors and flexors of a given part are located in the 

 part next proximad; thus the flexors and extensors of the upper 

 arm are grouped around the scapula, the flexors and extensors of 

 the forearm around the humerus, and the flexors and extensors of 

 the hand around the radius and ulna. Six groups of muscles of 

 the limb proper will therefore be considered. 



The only muscles which do not fall into any of the above eight 

 groups are the supinator and the pronator quadratus. These two 

 muscles have not been taken into account in the volumetric work. 



In the groups given below the individual muscles are listed in 

 the order of their size in the gopher, the largest being placed first. 



Group 2. Muscles from the body to the humerus; these muscles 

 pull the arm downward and backward: ^ . 





6 



Latissimiis dorsi 





116 



Pectoralis secundus 





lie? 



Pectoralis quartus 





11a 



Pectoralis primus 





1 



Cutaneus maximus 



Group 



3. 



Extensors of the upper arm 





16 



Supraspinatus 





14a 



Acromiodeltoideus 





14& 



Spinodeltoideus 





26 



Coracobrachialis 



Group 



4. 



Flexors of the upper arm : 





20 



Subscapularis 





17 



Infraspinatus 





15 



Abductor bracMi inferior 





18 



Teres major 





19 



Teres minor 



