90 Journal of Comparative Neurology. 



nests, he thinks their presence is due to an accidental arrangement 

 of the dendrites. The fact that these pericellular nests are al- 

 ways extra-capsular, and that therefore the several dendritic 

 processes which participate in their formation are not in con- 

 tiguity with the cell bodies of the neurons which they surround 

 argues very strongly against Cajal's hypothesis. 



The statement has just been made that the dendrites 

 break up into branches which terminate in the respective gan- 

 glia. Dogiel (25) has however shown that a few of the dendrites 

 of some of the neurons in a ganglion pass beyond the bounds 

 of said ganglion, enter a nerve trunk coming to, or leaving the 

 ganglion and thus reach a neighboring ganglion, where, after 

 undergoing division, they terminate. Such branches, he states, 

 resemble very closely non-meduUated nerve fibers, and only 

 when they can be traced to the cell from which they spring, 

 and when it can be made out that from the same cell there 

 arises an axis-cylinder, can the true nature of these protoplasmic 

 branches be ascertained. 



Ncuraxes of sympatJictic neurons. — S}'mpathctic neurons are 

 no exception to the very general rule, that a weuron has only 

 one neuraxis. The neuraxis may spring directly from the cell 

 body, as is commonly the case, or from one of the dendrites. 

 In the former case the neuraxis has its beginning in a cone- 

 shaped extension of the cell body. In the latter case it may 

 arise from any portion of a dendrite. In some cases, as for in- 

 stance in the larger cells of the sympathetic ganglia of reptilia, 

 all processes — neuraxis and dendrites — have their origin in a 

 single large process, which in turn arises from the depth of a 

 depression seen on one side of the cell body. Even in such 

 cells the neuraxis may arise from a dendrite, at a variable dis- 

 tance from the cell body. The fact that a neuraxis may be 

 given off from a dendrite, is only another proof of the opinion 

 now very prevalent, that the dendrites are only extensions of 

 the cell protoplasm, and will therefore receive no further dis- 

 cussion. 



In describing the structure of the neuraxes of sympathetic 

 neurons I shall follow very closely a summary by KoUiker (32), 



