f 
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course of an irritation producing a reflex-movement is therefore for 
this reason alone not maintainable. 
Before we enter into the inquiry of how a combination between 
the nerve-tubes is produced, we will examine if there is any mor- 
phological difference to be observed between motoric nerve-tubes 
and sensitive nerve-tubes. 
As is above stated the nerve-tubes of the dorsal (posterior) 
nerve-roots of the spinal cord of Myxine subdivide, immediately 
after their entrance into the nerve-cord and thus lose their individu- 
ality, whilst the nerve-tubes of the ventral (anterior) nerve-roots 
retain their individuality and seem to spring directly from ganglion 
cells, whilst giving off slender side-branches. 
I have also observed similar conditions in the spinal cord of 
higher vertebrata. I have even been able to obtain here more 
complete observations on the subdivisions of the nerve-tubes of the 
posterior nerve-roots. 
My observations fully agree therefore with those of Prof C. 
GoLGI in this respect; and as GOLGI says, I think we are entided 
to assume that, in the spinal nerve-cord, the sensitive nerve-tuhes 
arise from a junction of slender nervous fibrillæ, whilst the motoric 
nerve-tuhes are direct continuations of nervous processes (from gang- 
lion cells) which hoivever give off slender side-hranches. If this is 
correct the opposite conclusion seems, also, to be admissible, at 
all events to a certain extent, viz, that nerve-tubes arising from a 
junction of nervous fibrillæ are sensitive nerve-tubes, whilst nerve- 
tubes springing directly from ganglion cells are motoric nerve-tuhes. 
In the brain of the vertebrata, we lind nerve-tubes originating in 
both ways, and hence, I think, there, is every reason to believe 
that the same morphological differences between motoric and sensi- 
tive nerve-tubes are there present. 
Having now settled what morphological difterence there appears 
between the origin of sensitive and motoric nerve-tubes in verte- 
brata, and seeing that in invertebrata quite a similar difference is 
present in the modes of origin of two kinds of nerve-tubes, I think 
we are entitled to conclude further: that in the nervous system of 
the invertebrated bilaterata there is the same morphological diffe- 
rence between the origin of the sensitive and the motoric nerve- 
tubes, as is found in vertebrata; viz. the sensitive nerve-tubes arise 
from a junction of nervous fibrillæ, whilst the motoric nerve-tubes 
spring directly from ganglion cells. 
Arrived at this conclusion, we will now consider the question, 
