78 



ANATOMY OP THE CENTEAL NERTOUS SYSTEM. 



Here the gray matter is constmcted almost exclusively of that heaping- 

 up of neuroblasts of which mention was made while discussing the em- 

 bryonic development. In section A of the figure one recognizes the anterior 

 and posterior columns of the spinal cord; but, since the section is from 

 the cervical region, it is noticeable that the dorsal columns touch a much 

 greater part of the periphery than is true at a lower level. 



In section B the posterior horns diverge from each other and the dorsal 

 epithelium of the central canal is used to form the Tela chorioidea. 



Fig. 40. — Four sections through the medulla, of a four- centimeter larva 

 of Salamandra maculata. 



Fow, on either side of the ventricle lie gray masses, destined, like the 

 posterior horns {col. dors.), to receive sensory nerves. In figure C such a 

 nerve — -the Vagus, which enters here — ^is represented. 



Note, at the same time, the increase of the posterior gray column (col. 

 dors.) as the point of entrance of the Vagus. Still farther above, at D, the 

 great Acusticus enters with one of its roots; and now one sees the relations 

 of the spinal cord quite changed; but a single glance backward of the figures 



