MYOLOGY 45 



tion is largely scrotal. In reality it is a development from 

 the internal oblique, and its fibers are to be found between 

 the laminae ectalis and entalis of the tunica vaginalis. 



The innervation of the cremaster is by means of the genito- 

 femoral nerve, and of the remaining abdominal muscles, 

 by branches of the lower thoracic nerves; but these were 

 not followed in the present instance. 



C. Lu7nhar muscle 



Under this heading there is but a single muscle — the 

 M. quadratus lumborum (figs. 12, 33), which occurs in 

 four separate bundles. The first arises from the ninth 

 thoracic vertebra and is inserted upon the diapophysis 

 of the second lumbar vertebra. The others occur similarly 

 save that the last has insertion upon the cranio-ventral 

 border of the spine of the ilium. 



This muscle is served by branches from the lumbar nerves. 



D. Muscles of the hack 



The muscles of the back are placed in two divisions — the 



1. Superficial, secondary back muscles 



2. Deep, intrinsic back muscles 



1. SUPEEFICIAL, SECONDARY BACK MUSCLES 



This more superficial group is further divisible into three 

 layers. 



First layer consists of four muscles, which are 



Mm. clavotrapezius spinotrapezius 



acromiotrapezius latissimus dorsi 



M. clavotrapezius (figs. 6, 7, 23, 24, 28, 29) has origin 

 which is continuous with that of the acromiotrapezius 

 along the occipital angle of the cranium extending from 

 just dorsad of the mastoid to the middorsal Hne, and 



