PRENTISS, Weurofibrillar Structures. 159 
other noted neurologists and with his own recent work on the 
regeneration of peripheral nerves. It is at least clear that as 
far as the evidence of histogenesis goes the neurone theory is 
still open to dispute. It is grounded on certain recognized facts, 
but these facts relate only to the early stages of development. 
Neither His nor Harrison says anything as to the origin of the 
neurofibrillae, structures upon which the opponents of the reu- 
rone theory put much weight. 
2. Neuropathology. GUDDEN (’89) was the first to demon- 
strate the fact that the cutting of a motor axis-cylinder caused 
the degeneration not only of the peripheral fiber, thus isolated 
from its cell, but also of the cell and its dendrites. In new-born 
animals the entire nerve element atrophied and was resorbed, 
but never in any case were the pathological changes observed 
beyond the dendrites of the injured neurone. According to 
Niss_, Foret (’86) first coupled these facts with the evidence 
of GoLGi’s preparations and formulated the idea of the nerve- 
cell individual, to which WALDEYER later gave the name of neu- 
rone. The two facts of neuropathology which have been used 
as arguments in support of the neurone theory are: (1) that 
nerve fibers separated from their ganglion cells degenerate and 
(2) that the phenomena of degeneration never have been ob- 
served to pass beyond the processes of the injured elements. 
The experiments of GupDEN show that it is not merely 
their isolation from their cells which causes nerve fibers to degen- 
erate, for the cells themselves often atrophy in young animals. 
BETHE ('98) by isolating the neuropil of a nerve center in the 
brain of the crab found that the nerve elements may remain 
actively functional for several days, proving that the nerve ele- 
ments are physiologically independent of their cells. His re- 
cent experiments in neuropathology, of which he has given 
only a preliminary account (: 02), show that peripheral nerves 
will degenerate some time after isolation from their nerve cells; 
furthermore, that in the young dog such degenerate nerve fibers 
will, in the course of 6 to g months, regenerate all the structures 
of anormal nerve fiber—primitive fibrillae, perifibrillar substance and 
Schwann's sheath. Not only are the regenerated fibers normal 
