186 MYOLOGY. 



Relation, — Externally with the levator humeri, cervical trape- 

 zius, serratus magnus, and rhomboideus muscles ; internally with 

 the complexus major, trachelo-magtoideus, and obliquus capitis 

 tnuscles. 



Action. — With its fellow it elevates the head; alone it draws 

 the head to one side. 



TRA.CHELO-MASTOIDEUS.* 



{Dorso-mastoideus.) 



(Fig. 73.6.) 



Situated under and along tbe inferior border of the splenius,, 

 it is elongated and fleshy, its fibres passing forwards and 

 upwards; the belly is divided into two portions, which run 

 parallel, each terminating by a tendon anteriorly. 



Origin. — From the transverse processes of the first two dorsal 

 and the oblique processes of the last five cervical vertebrae. 



Insertion. — By two tendons; one to the wing of the atlas, 

 common also to the splenius and levator humeri; the other, 

 continuous with that of the splenius, to the mastoid ridge. 



Relation. — Externally with the splenius ; internally with the 

 spinalis colli ; posteriorly with the longissimus and spinalis dorsi. 



Action. — With its fellow to erect the head ; acting alone, it 

 draws it to one side. 



COMPLEXUS MAJOR. 



(Dorso-occipitalis.) 



(Fig. 73. a.) 



Situated on tbe inside of the splenius, this muscle resembles 

 an elongated triangle, with the base backwards .; it is fleshy, with 

 tendinous intersections. The posterior part is aponeurotic at its 

 origin, the anterior terminating in a single tendon. 



Origin. — From the transverse and spinous processes of the 

 first five dorsal, and the oblique processes of all the cervical 

 vertebrae. 



Insertion. — To the side of the occipital tuberosity. 



Relation. — Externally with the splenius and trachelo- 

 mastoideus; internally with the complexus minor, ligamentum 

 nuchae, and oblique muscles ; posteriorly with the longissimus 



* This is the complexus minor of M. Chauveau. 



