NEUROLOGY 281 



THE SPINAL NERVES 



The first pair of spinal nerves come out between the atlas and -the 

 occipital bone. Each nerve divides into three branches. The first 

 is the anterior branch which innervates the dorsalis, the biventer 

 cervicis, the cervicales, and the caput posticus muscles. The sec- 

 ond is the recurrent ventralis which passes mesially and downward 

 from the recurrent communicans. It innervates the rectus capitis 

 anticus muscle and joins a branch of the hypoglossal nerve. There 

 is given off a white ramus communicans to the sympathetic nerve. 



The second spinal nerve emerges from the opening between the 

 first and the second cervical vertebrae and is similarly disposed as 

 the first cervical. It gives off a branch called the recurrent ventralis 

 which fuses with branches of the first cervical and the hypoglossal 

 nerve. This nerve innervates the complexus muscle. 



The succeeding cervical nerves emerge in a similar manner down 

 the neck and are distributed to the muscles and other structures of 

 the cervical region. The second, the third, and the fourth cervical 

 nerve gives off branches which form anastomosing loops with the 

 facial nerve. 



According to Gadow the last cervical nerve passes between the 

 last cervical and the first dorsal segment. There are thus fifteen 

 pair of cervical nerves. 



The first pair of dorsal nerves pass out between the first two dorsal 

 vertebrae. The first few dorsal nerve branches innervate only the 

 trunk muscles. Other branches supply the skin and the other 

 adjacent integument. The ventral branches of the cervical nerves 

 often communicate with the ventral branches of the first dorsal 

 nerves. These branches are larger than the superior branches and 

 aid in the formation of the bracial plexus. Smaller inferior branches 

 are distributed to the scalenus and other muscles, and extend as far 

 posterior as the intestines. 



The dorsal branches of the spinal nerves in the lumbo-sacral 

 region are very small, on account of the lack of extensive develop- 

 ment of the muscles of this region. The elements entering into these 

 nerve trunks are largely vasomotor nerves. In addition to the 

 upper twigs supplying the skin and the other integument of the 

 region, other branches descend into the abdominal cavity. 



The caudal spinal nerves are not well developed and disappear 

 in the region of the caudal vertebrae. The dorsal branches inner- 



