58 ANATOMY OF THE WOOD RAT 



origin for about 4 mm. from the caudal border of the ischium, 

 with insertion upon the latero-distal portion of the body of 

 the urethra. It invests a part of the corpus cavernosum. 



M. bulbocavernosus (fig. 21). The homology of this 

 with the muscle of the same name in the cat is uncertain 

 because of the fact that what are herein termed the bulbs 

 of the corpora cavernosa urethrae or corpora spongiosa, 

 may be a separate organ with special function. At any 

 rate, the fibers of this muscle, which are defined with some 

 difficulty in animals which are sexually inactive, run 

 obliquely laterad as they pass forward, investing the 

 medial portion of each bulb. 



M. compressor urethrae (fig. 21) is an unpaired muscle 

 in the male, its fibers running in a circular course about 

 the body of the urethra. 



MUSCLES OF THE ANTERIOR LIMB 



The muscles of the anterior hmb fall naturally under the 

 following headings: 



A. Muscles of the shoulder girdle 



B. Muscles of the upper arm 



C. Muscles of the forearm 



D. Muscles of the hand 



A. MUSCLES OF THE SHOULDER GIRDLE 



The muscles of the shoulder girdle number seven, as 

 follows : 



Mm. supraspinatus teres minor 



infraspinatus teres major 



clavo-acromiodeltoideus subscapularis 

 spinodeltoideus 



M. supraspinatus (figs. 6, 13, 28, 29) occurs in two 

 parts which are separable with fair ease. The more super- 

 ficial one, whose ectal belly is invested with an aponeurosis, 

 arises from the entire dorsal border of the spine of the 



