52 NEBVOUS SYSTEM. 



single and sometimes bifurcated, and which pass, in by far 

 the greatest number if not in all instances, to the periphery. 



The multipolar cells, with three or more prolongations, 

 are found in all of the ganglia, but they predominate largely 

 in the gray matter of the cerebro-spinal centres. It is the 

 question of the exact mode of connection between these cells 

 and the fibres of origin of the cerebro-spinal nerves and the 

 union of the cells with each other by commissural prolonga- 

 tions, that presents the greatest difficulty and uncertainty. 

 One point, which has been raised within a few years, is with 

 regard to the character of the different poles connected with 

 the same cell. In ordinary preparations of the central ner- 

 vous system, it is impossible, even with the highest available 

 magnifying powers, to distinguish any one pole which, in its 

 general characters and connections, is different from the 

 others ; yet, some of the anatomists to whose researches we 

 have alluded describe a single pole, more distinct in its out- 

 lines than the others, which does not branch and is to be re- 

 garded as an axis-cylinder. The other poles are supposed to 

 be of a different character, not connected with the nerve- 

 fibres, and always presenting a greater or less number of 

 branches. These views are accepted by Schultze, who gives a 

 figure, after Deiters, in which the contrast between the poles 

 is represented as very marked ; 1 but although this opinion 

 is accepted by other high authorities, 8 it is not easy to un- 

 derstand how it can be received without reserve, when it 

 is 'so difficult, if not impossible, to follow out the poles, ex- 

 cept for a very short distance. 



"With our present means of investigation, there seems to 

 be no doubt with regard to the following facts : Tracing 

 the nerve-fibres toward their origin, they are seen to lose 

 their investing membrane as soon as they pass into the 

 white portion of the centres, being here composed only 



1 STRICKER, Manual of Human and Comparative Histology, London, 1870, 

 vol. i., p. 1T7. 



2 KOLLIKER, fitiments (Phistologie humaine, Paris, 1868, p. 362 



