THEORIES OF NERVE STRUCTURE 155 



tions which divide up the longitudinal cavities, and not threads 

 merely, yet this seems to follow with great probability from the 

 indubitable fact that the apparent longitudinal fibrillse represent 

 a honeycombed structure. When we then further see that the 

 structure of the nerve fibre corresponds entirely to the structure 

 of ordinary fibrous protoplasm, and at the same time are able to 

 render probable, from a whole series of reasons, the fact of 

 alveolar structure of protoplasm, it seems to me that the inter- 

 pretation of the cross threads as partitions is proved to be the 

 only plausible one. If we further take into consideration the 

 great agreement between the structure of the processes of 

 ganglion cells and that of the axis-cylinder, and also the fact 

 that axis-cylinders may pass directly, in their entire mass, into 

 ganglion cells, it seems to me certain that the axis-cylinder is 

 nothing but a strand of protoplasm, the structure of which has 

 become modified into a fibre-like meshwork in correspondence 

 with the modification which tracts of protoplasm generally 

 undergo when stretched out lengthways, and which is, as a rule, 

 distinguished from ordinary protoplasm, including that of the 

 ganglion cells, by its feeble staining powers in the usual colour- 

 ing media. The latter circumstance may, however, depend 

 principally on the small number arid the fineness cf the granules 

 deposited in it, which are generally the cause of intense tingi- 

 bility in protoplasm. 



Although Joseph (1888), as has been remarked above, reached 

 a step farther in observation, he remained, to my mind, far 

 behind Nansen in the interpretation of what had been seen. In 

 his view the reticulation observed both in transverse and longi- 

 tudinal section of the axis-cylinder is a framework which is a 

 direct continuation of that of the medullary sheath. We are 

 thus concerned with a supporting framework to the axis- 

 cylinder ; the true nervous substance would be the intervening 

 substance, just as Nansen also supposed. Now, although 

 Joseph naturally found this substance always homogeneous and 

 structureless, he yet thinks it possible to maintain the unten- 

 able view that it is in reality fibrillar. On this view the fibrilla- 

 tion in the axis-cylinder observed by M. Schultze and so many 

 others would belong to this intervening substance ; treatment 

 with osmic acid is supposed to be unsuitable for rendering the 

 real nerve fibrillse visible. I think, however, that every one will 

 allow that the longitudinal fibrillse seen by Joseph are the same 

 that M. Schultze and his successors termed the fibrilla? of the 

 axis-cylinder, the more so as osmic acid was just the reagent 

 most in favour for demonstrating these fibrillae. I therefore 

 consider Joseph's assumption of a special kind of nervous fibrillse, 



