160 JOURNAL OF COMPARATIVE NEUROLOGY. 
in structure, but stimulation of the distal stump of the nerve 
(Ischiadicus) causes contraction of the muscles which it sup- 
plies. Upon dividing the regenerated nerve a second time, 
degeneration ensued in the distal portion only. By this evi- 
dence of BETHE’s the phenomena of degeneration, in themselves, 
are rendered worthless as arguments in support of the neurone 
theory, while his observation of the regeneration of peripheral 
nerves is incompatible with the assumption that each nerve 
fiber develops in its entirety as a process of a single ganglion 
cell. 
That the phenomena of degeneration have not been ob- 
served to pass beyond the dendrites of the injured nerve ele- 
ments is most easily accounted for by assuming the non-exist- 
ence of continuity between the dendrites of the nervous ele- 
ments. But, as Nisst argues, the opponents of the neurone 
theory may, with equal right, assume the presence of connecting 
fibrillar structures in the central organ, of whose peculiar qual- 
ities we as yet know nothing, at least in vertebrates. These 
structures (the ‘‘nervose Grau” of Nissx) are differentiated cell 
products, and as they are independent of the ganglion cells, 
they are immune from the pathological changes which affect the 
processes of the latter. What are the histological facts in sup- 
port of these assumptions ? 
3.  Astology. We have seen that the neurone theory 
was based by Foret and WaLDEYER mainly upon the discov- 
eries of His, and the silver impregnations of GoLai and Ramon 
y CajaL. It is now known that the methods of GOLGI are ex- 
tremely unreliable, that the impregnations are rarely complete 
and often extend to non-nervous structures. When, therefore, 
ApATuHy ('97) demonstrated by new methods the finer structure 
of the nervous system, many neurologists maintained that 
the neurone theory had received its death blow. The 
value of ApATHY’s work, however, has been in throwing into 
doubt the evidence of GoLG! preparations, and showing the 
importance of more certain and refined methods for the study 
of the nerve elements. APATHY proved that the supposed 
nervous units of GoLGi preparations are themselves composed 
