130 Journal of Comparative Neurology. 



cellular hypothesis not only regarding its origin but its persist- 

 ent existence, is described as being cellular in its origin but 

 consisting largely of fibers independent of cells in its later 

 stages. The neurones, or nervous substance in the narrower 

 sense of the word, used to be looked upon as a mass of fibers, 

 a few (the peripheral motor fibers at least) in distinct connection 

 with the cells from which they grow, others originating from the 

 network of the spongy substance and only indicating connec- 

 tion with cells and masses of cells. Now we wish to establish 

 for the nerve elements just that view which was held for the 

 neuroglia, and which was dethroned by Weigert. We tried 

 this notwithstanding certain difficulties concerning the monocel- 

 lular character of the peripheral nerve-fibers. The peripheral 

 nerve-fibers consist after all of more than one cell, unless we 

 have it strictly understood that the cell-unit consists only of the 

 nerve cell-body, dendrites and axis-cylinder process, and that 

 the sheath and its nuclei are an additional coat, not really be- 

 longing to the cell-unit, but formed by epiphytes. If we fol- 

 low Vignal and Ranvier, we assume that the myelin sheath 

 and the nuclei of the inter-nodes have nothing to do with the 

 neurone itself, but are mesoblastic epiphytes. If, however, we 

 follow other observers who consider the myelin sheath a pro- 

 duct of the axis-cylinder, the difficulty with the ' epiphytes ' 

 would be shifted ; especially the effect of secondary degen- 

 eration on the myelin would be free of serious contradic- 

 tion with the neurone-concept as a 'one-cell-concept.' How- 

 ever this be, we should make the mental reservation, when 

 speaking of a motor cell-unit or neurone, that we do not in- 

 clude the nuclei of the internodes, i. e. do not speak of all that 

 is usually included in the description of a ' fiber; ' further, that 

 there still is some uncertainty as to whether the myelin be- 

 longs to the neurone or the epiphytes. 



There are two points to be mentioned that will relieve our 

 fears of the analogy with the fate of the neuroglia. The first 

 one lies in the nature of Weigert's arguments. According to 

 him the neuroglia is a real intercellular substance, i. e. 'non- 

 nervous material belonging to the group of modified cell-sub- 



