THE NEURON 



45 



from the cell body; it may arise from the base of one of the den- 

 drites or, rarely, from the apex of the chief dendrite (Fig. 11). 



Neurons differ in internal structure, as well as in form, from 

 the other cells of the body. The most important of these pecu- 



Fig. 10. A collection of cells from the ganglion of the trigeminus of the 

 embryonic guinea-pig, to illustrate various stages in the transformation of 

 bipolar neuroblasts into unipolar ganglion cells. (After Van Gehuchten.) 



liarities are, first, the fibrillar structure of their cytoplasm, 

 and, second, the presence in the cytoplasm of a highly complex 

 protein substance chemically allied to the chromatin, which is 



Fig. 11. A neuron from the primary gustatory center in the medulla 

 oblongata of the carp. (Figure 136 (2), p. 303, illustrates the enormous 

 enlargement of the medulla oblongata of this fish which is produced by this 

 gustatory center.) The peripheral gustatory nerves end among the 

 dendrites, d. The axis of the main dendrite is directly prolonged to form 

 the axon, a. The heavy line at the right marks the external surface of the 

 brain. (From the Journal of Comparative Neurology, vol. xv, p. 395.) 



the best known and probably the most important constituent of 

 the cell nucleus. This is the chromophilic substance, which in 

 nerve-cells as seen under the microscope is ordinarily arranged 

 in more or less definite flake-like masses scattered throughout 



