460 THE AMERICAN NATURALIST.  [Vor. XXXIV. 
had previously presented. In both vertebrates and inverte- 
brates it was early recognized that this finely fibrous material 
was directly continuous with the living substance of both nerve 
fibres and ganglion cells, and therefore formed an integral part 
of the nervous organs. To this substance, whether it be from 
vertebrates or invertebrates, His gave the convenient name of 
* neuropile." 
As no other material aside from the three his far Me 
ered has been found to be necessarily connected with nervous 
organs, we may regard such organs as made up of a combina- 
tion of nerve fibres, ganglion, or, as they are often called, nerve 
cells, and neuropile. The mutual relations of these three 
materials must next be considered. 
The problem of the relation of these nervous materials has 
been discussed chiefly from the standpoint of the anatomical 
origin of nerve fibres. When a nerve fibre is traced into a 
central nervous organ, from what is it found to take its origin ? 
Does it pass out from a ganglion cell, does it originate from 
the neuropile, or does it come from some other source? This 
is what is meant by the anatomical origin of nerve fibres, and, 
on this question the earlier neurologists were divided into three 
schools. First, there were investigators, like Buchholz, who 
attempted to maintain that all nerve fibres arose directly from 
ganglion cells. Next, there were those who, with Leydig at 
their head, believed that nerve fibres were formed by a drawing 
together of many fibrils in the neuropile, whereby the transmit- 
ting core of a fibre was established. The advocates of this 
view also believed that the fibrils of the neuropile were derived 
from the finely divided processes of ganglion cells, and that, 
therefore, nerve fibres were connected with gangliom cells 
through the neuropile. Hence they rightly designated their 
view as that of the indirect origin of nerve fibres as contrasted 
with the origin of these structures directly from ganglion cells. 
Finally there were those who, like Gerlach, maintained that 
both methods of origin occurred, ż.e., that some fibres arose 
directly from cells and others indirectly through the neuropile. 
In support of this opinion Gerlach instanced the condition of 
the spinal nerves in vertebrates (Fig. 1), in which the dorsal 
