MUSCLES OF THE SUPERIOR EXTREMITIES. 359 



MUSCLES OF THE SUPERIOR EXTREMITIES. 



THESE may be divided into the muscles that are situated on 

 the scapula, on the os humeri, on the cubit or forearm, and on 

 the hand. 



Muscles situated on the Scapula. 



These are called muscles of the os humeri ; and are three 

 behind, one along its inferior costa, two before, and one beneath 

 it. 



Behind are, 



1 . Supra-spinatus , 



Arises, fleshy, from all that part of the base of the scapula 

 that is above its spine ; also from the spine and superior costa ; 

 passes under the acromion, and adheres to the capsular ligament 

 of the os humeri. 



Inserted, tendinous, into that part of the large protuberance 

 on the head of the os humeri, that is next the groove for lodging 

 the tendon of the long head of the biceps. 



Use. To raise the arm upwards ; and, at the same time, to 

 pull the capsular ligament from between the bones, that it may 

 not be pinched. 



2. Infra-spinatus, 



Arises, fleshy, from all that part of the base of the scapula 

 that is between its spine and inferior angle ; and from the spine 

 as far as the cervix of the scapula. The fibres ascend and 

 descend obliquely towards a tendon in the middle of the mus- 

 cle, which runs forwards, and adheres to the capsular ligament. 



Inserted, by a thick and short tendon, into the upper and 

 middle part of the large protuberance on the head of the os 

 humeri. 



Use. To roll the humerus outwards : to assist in raising, and 

 in supporting it when raised ; and to pull the ligament from 

 between the bones. 



