186 MYOLOGY. 



Relation. Externally with the levator humeri, cervical trape- 

 zius, serratus magnus, and rhomboideus muscles ; internally with 

 the complexus major, trachelo-mastoideus, and obliquus capitis 

 muscles. 



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

 the head to one side. 



TRACHELO-MASTOIDEUS.* 



(Dorso-mastoideus. ) 



(Fio. 73. b.) 



Situated under and along the 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 spinahs dorsi. 



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

 draws it to one side. 



COMPLEXUS MAJOR. 



( Dorso-occipitalis. ) 



(Fie. 73. a.) 



Situated on the 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 

 vertebra?. 



Insertion. To the side of the occipital tuberosity. 



Relation. Externally with the splenius and trachelo- 

 mastoideus ; internally with the complexus minor, ligamentum 

 nuchaB, and oblique muscles ; posteriorly with the longissimus 



* This is the complexus minor of M. Chauveau. 



