352 MUSCLES OF THE BACK. 



backwards laterally : and, when both act, to pull the head 

 directly backwards. 



N. B. Albinus divides this muscle into two, viz. That por- 

 tion which arises from the five inferior spinous processes of the 

 neck, and is inserted, into the mastoid process and os occipitis, 

 he calls splenius capitis ; and that portion which arises from 

 the third and fourth of the ttack, and is inserted into the five 

 superior transverse processes of the neck, is called by him 

 splenius collL 



The single pair, 



Serratus Superior Posticus, 



Arises , by a broad thin tendon, from the spinous processes 

 of the three last vertebrae of the neck, and the two uppermost 

 of the back. 



Inserted into the second, third, fourth, and fifth ribs, by as 

 many fleshy slips. 



Use. To elevate the ribs, and dilate the thorax. 



The third layer consists of three pair on the back, and three 

 on the neck. 



Those on the back are, 



1. Spinalis Dorsi, 



Arises from the spinous processes of the two uppermost ver- 

 tebrae of the loins, and the three inferior of the back, by as 

 many tendons. 



Inserted into the spinous processes of the nine uppermost 

 vertebrae of the back, except the first, by as many tendons. 



Use. To erect and fix the vertebrae, and to assist in raising 

 the spine. 



2. Longissimus Dorsi, 



Arises, tendinous without, and fleshy within, from the side, 

 and all the spinous processes of the os sacrum ; from the poste- 

 rior spine of the os ilium ; from all the spinous processes, and 

 from the roots of the transverse processes of the vertebrae of the 

 loins. 



