3IR. J. L. CLAEKE ON THE GEET SHBST^iNCE OF THE SPINAL COED. 457 
tion of some hundreds of preparations, I have never been able to perceive that the 
epithelial-processes are connected vrith any other than the small cells or nuclei which I 
have akeady described. I have sometimes seen the process of a large werw-cell extend 
close up to the epithelium, but I have generally succeeded in tracing it round the 
canal to the opposite side of the cord*. If the processes of the epithelial-cells were 
dkectly continuous with, and formed elementary parts of, nerve-ce]ls, and nerve-fihxes,, 
we might reasonably expect to find the number of the former always in proportion to 
that of the latter ; but the very reverse is the case ; for, as we have just seen, in the 
filuni terminate^ where both nerve-ce\h and nerve-^hxes, have entirely disappeared, the 
canal is much larger, and the epithelial-cells are consequently much more numerous than 
in any other region; while, as I have akeady shown, their processes may be traced 
through the surrounding white substance as far as the surface of the cord. 
I have nothing to add to the description which I formerly gave of the anterior joots 
of the spinal nerves, except that in the conus medullaris I constantly find that some of 
the fibres of these roots terminate in loops round the group of cells in the anterior cornu ; 
but whether they be really nerve-Qbre^ I have not quite satisfied myself. Sometimes 
they form loops between two difierent bundles of roots, and sometimes a fibre from one 
bundle returns in a loop to the inner or outer side of the anterior column. But in the 
same region of the cord I have seen the processes of the nerve-cells extend so frequently 
into the anterior roots, that there can be no doubt that some of the latter arise from 
themf. In the cervical and lumbar regions of the Tortoise, but especially in the lumbar 
enlargement, the course and connexions of the processes proceeding from the cells of 
the anterior cornua are extremely interesting. Fig. 44, Plate XXV. represents a trans- 
verse section of one lateral half of the grey substance, through the middle of the lumbar 
enlargement. From the whole of its lateral border numerous large bundles of fibres 
proceed outwards and form with each other a beautiful network between fasciculi of 
the antero-lateral column. Some of these fibres converge from the central parts of the 
grey substance ; the rest proceed from the roots of the nerves, and from the cells of both 
the posterior and anterior cornua, but particularly from the latter. The large cells of 
each anterior cornu form a considerable group ; they are angular, sigmoid, crescentic 
and fusiform, and elongated to an extraordinary degree in a direction obliquely back- 
wards. The processes from thek anterior extremities are continuous with the anterior 
Entferuung yora Mittelstiick mit einander verschmelzen, mid in eine Nervenzelle iibergelien, reap., den 
Fortsatz einer Nei’venzelle sich dichotomisch oft tridiotomisch theilen und in zwei oder drei Epithelial- 
cylindern endigen.” “ Es ist mir abev sehr wabrscheinlicb, dass diese Auslaufer oder peripheriscben Enden 
der Epitbelialzellen als Elementarrbrchen der betreffenden Primitivnervenfaser oder Nervenzelle, in w6lehe 
sie eintreten, bestebeu.” — Neue TJntersuchnngen, Erste Lieferung, p. 11 (1857). 
In the coccygeal region of the cord, processes from the nerve-cells in the anterior cornu may be very 
distinctly seen to cross both va. front and ieTiind the canal to the opposite side. 
t I never, as Schuoder van dee Kolk asserts, denied the connexion of nerve-fibres with processes of 
cells, hut simply maintained that the occasional extension of these processes into nerve-roots was not a 
sufficient proof of such a connexion, for they might be distributed to blood-vessels. 
