354 



THE PERIPHERAL NERVOUS SYSTEM 



the cord as the dorsal root fibers (Fig 358). These fibers course in the 

 dorsal funiculi and eventually form the greater part of them. Peripheral 

 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 ganglion crest between the 

 spinal ganglia have begun to disappear. In transverse sections at this 



Ophthal. din. 



Sup. max. div. 

 M. masticatorius 



Inf. max. div. 



I X-X- XI gang, crest 



S.I. 



D.I. 



FIG. 358.- 



L. I. 



-Reconstruction of a 6.9 mm. embryo, showing the development of the dorsal root 

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



stage (Fig. 325 and 360) the different parts of a spinal nerve may be seen. 

 The trunk of the nerve, just ventral to the union of the dorsal and 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 



