354 



THE PERIPHERAL NERVOUS SYSTEM 



eventually form the greater part of them. Perpiheral processes of the ganglion 

 cells join the ventral root fibers in the trunk of the nerve (Fig. 360). At 10 mm. 

 (Fig. 359) the dorsal root fibers have elongated and the cellular bridges of the 

 ganghon crest between the spinal gangha have begun to disappear. In transverse 

 sections at this stage (Fig. 325 and 350) the different parts of a spinal nerve may 

 be seen. The trunk of the nerve just ventral to the union of the dorsal and 



IX-X-XI gang, crest 



Ophthal. div. 



Sup. max. div. 



M. masticatorius 



Inf. max. div. 



S.I. 



Fig. 358. — Reconstruction of a 6.9 mm. embryo, showing tlie development of the dorsal root fibers from 

 the spinal and cerebral ganglia (Streeter). X 16.7. 



ventral roots gives off laterally the dorsal, or posterior ramus, the fibers of which 

 supply the dorsal muscles. The ventral ramus continuing gives off mesially the 

 ramus communicans to the sympathetic ganglion and divides into the lateral and 

 ventral (anterior) terminal rami. The efferent fibers of these rami supply the 

 muscles of the lateral and ventral body wall, and the afferent fibers end in the 

 integument of the same regions. 



