THE NERVE CELL 



111 



FIG. 109. INTRACELLULAR 

 NETWORK WITHIN A PlJR- 

 KINJE CELL OF THE CERE- 

 BELLUM or " STRIX FLAM- 



MEA." 



Golgi's stain. (After Golgi.) 



separates them from the surrounding tissue. This is presumably 

 a lymphatic or tissue juice space. Holmgren has recently demon- 

 strated, also, the presence, within the cytoplasm of the nerve cell, 

 of minute canaliculi which form an intra- 

 cellular network, more abundant near the 

 surface of the cell, and which he has termed 

 juice canaliculi (Saftkancilchen). These 

 canaliculi may possibly account for the pe- 

 culiar intracellular network which Golgi 

 has recently demonstrated in the periph- 

 ery of the nerve cell by a modification of 

 his rapid silver impregnation method. 



The processes of the nerve cell are of 

 two varieties : the one, broad, granular, 

 and rapidly dividing in the vicinity of the 

 cell body into a number of branching sub- 

 divisions, is the dendrite ; the other, long, 

 slender, and finely fibrillar, arises from 

 the cell body direct, or from the base of 

 a dendrite, and, passing for a consider- 

 able distance from the cell body, finally 

 enters the nerve fibre as its axis cylinder, or terminates in relation 

 to some distant nerve cell. This latter process is the neuraxis. 

 Each cell body usually possesses a single neuraxis and several den- 

 drites. Cells without a neuraxis are found in the retina and in 

 the olfactory bulb ; except for these, all nerve cells in the body of 

 man possess a neuraxis and usually but one such process. The 

 subdivision of nerve cells into uni-, bi-, and multi-polar cells is, 

 therefore, chiefly based upon the number of their dendrites. 



Dendrites (protoplasmic processes). The dendrites of a nerve 

 cell vary from one to a considerable number. They arise from 

 the cell body by a broad stem, and quickly break into branches 

 which can be traced for a considerable distance in fact, the arbor- 

 ization of the dendrites is usually so extensive that it can be fol- 

 lowed for only a short portion of its course. Occasionally dendrites 

 do not branch until they have arrived at a considerable distance 

 from their parent cell body. 



The structure of the dendrite is, to all appearances, similar to 

 that of the cell body. The stainable substance of Xissl is con- 

 tinued for some distance into the arborizing dendrites, which 

 often possess a finely fibrillar appearance. In Golgi-stained prepa- 



