MUSCLES OF THE BACK. 407 



The Trachelo-Mastoideus, 



Is at the inner side of the last muscle, in contact with it. 



It arises by distinct tendinous heads, from the transverse 

 processes of the three superior vertebrae of the back, and of the 

 five inferior of the neck ; and is inserted, by a thin tendon, into 

 the posterior edge of the mastoid process. 



The dorsal origins are frequently deficient or irregular. 



It draws the head backwards. 



The Complexus, 



A fine large muscle, is situated at the inner face of the tra- 

 chelo-mastoideus, and is readily recognised by showing itself 

 between the bellies of the two splenii capitis, just below the 

 occiput. A quantity of tendinous matter exists in its middle, 

 which gives it the complicated appearance from whence its 

 name is derived. 



It arises, by tendinous heads, from the seven superior dorsal, 

 and the four inferior cervical vertebrae, by their transverse pro- 

 cesses; also, by a fleshy slip from the spinous process of the 

 first dorsal. It is inserted into the inferior part of the os occi- 

 pitis, by the surface between the upper and lower semicircular 

 ridges, on the outside of the vertical ridge which exists in the 

 middle of the bone. 



It draws the head backwards. 



The Semi- spinatis Cervicis, 



Is a muscle which passes obliquely from transverse to spi- 

 nous processes, and is situated between the complexus and the 

 multifidus spinae; the course of its fibres renders it difficult to 

 be distinguished from the latter. 



It arises from the transverse processes of the six upper ver- 

 tebrae of the back, by tendons which adhere to those of the ad- 

 jacent muscles; and passes up to the neck, to be inserted into 

 the sides of the spinous processes of the five middle cervical 

 vertebrae. 



It extends the neck obliquely backwards. 



