THE CENTRAL NERVOUS SYSTEM 



665 



scattered, but probably 

 they are as widely dif- 

 fused as the large nerve- 

 cells proper, and no ex- 

 tensive area of the grey 

 matter is wholly without 

 them. 



Although there are 

 several varieties of gran- 

 ules (Hill), they all agree 

 in this, that their axons 

 run a comparatively 

 short course, and never, 

 or rarely, pass beyond 

 the grey matter. Another 

 kind of neuron which is 

 also confined to the grey 

 matter, and is typically 

 seen in the cortex of 

 the cerebrum and cere- 

 bellum, presents the 

 peculiarity of an axon 

 which branches into an 

 intricate network im- 

 mediately after coming 

 off from the cell (cell 

 of Golgi's second type). 

 Unlike the long axon 

 of the typical large 

 nerve-cell, the axis-cylin- 

 der process of this Golgi 

 cell remains unmedul- 

 lated. 



The sympathetic gan- 

 glion cells, which are 

 developed from imma- 

 ture neuroblasts that 

 migrate, in the coutse 

 of development, from 

 the spinal ganglia, and 

 gathering in clumps form 

 the ganglia of the sym- 

 pathetic chain (His), 

 agree in general with the 

 cells of the cerebro spinal 

 axis in possessing an 

 axon and one or more 

 dendrites, although a few 

 of them are devoid of 

 dendrites. 



The epithelium lining 



FIG. 231. SCHEME OF LOWER MOTOR NEURON 

 (BARKER). 



a. h, axon-hillock (the portion of the cell from which 

 the axon comes off), containing no Nissl bodies, and 

 showing fibrillation ; ax, axis-cylinder or axon ; 

 tn, medullary sheath, outside of which is the neuri- 

 lemma ; c, cell-substance (cytoplasm), showing Nissl 

 bodies in a lighter ground substance ; d, protoplasmic 

 processes or dendrites containing Nissl bodies ; 

 n, nucleus ; n', nucleolus ; n. R t node of Ranvier ; 

 s. f, side fibril ; n of , nucleus of the neurilemma ; 

 tel. t motor end plate; m', striped muscle fibre; 

 j. L, incisure. 



