THE LUMBAR ENLARGEMENT OF THE SPINAL CORD. 339 
the only difference between these authors being one of degree; Stilling maintaining 
that some only of the fibres constituting the anterior roots arise from cells within the 
cord, the remainder being direct continuations of the posterior roots; on the other 
| hand, Bidder and Schróder van der Kolk consider the cells of the anterior cornua the 
sole origin of the anterior roots. Clarke in his more recent papers acknowledges the 
cells as a partial source of origin for the roots; he says, *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 them."* He also describes and figures this as occur- 
ring very frequently in the lumbar and cervical region of the tortoise. That the ante- 
rior roots are derived partly at least from nerve-cells, is beyond doubt; the principal 
groups of cells in the anterior cornua are however usually situated at some distance 
from the border of the gray substance, so that it is often quite difficult to trace these 
connections; but I have sometimes (though I must admit very rarely) succeeded in 
tracing, in the cords of small animals, fibres derived from cell processes, not only into 
the bundle of anterior roots, buf quite to their exit from the cord. This is shown as 
seen in the cord of the rabbit (Fig. 1, a’). Fig. 4 shows a group of cells sending 
their processes into the anterior roots at A; the four cells marked 5 are connected with 
the bundle of anterior roots by very long, slender processes, and are also connected 
with each other and with neighboring cells. This is a very interesting group, though, 
owing to its lying at some distance within the boundary of the cornu, comparatively 
few of the processes could be traced out into the bundle of roots. Fig. 5 is from a 
longitudinal section through the anterior cornu; the group of cells is situated quite 
near the white substance, and a number of cell processes can be traced out into the 
bundles of fibres forming the anterior roots (Fig. 5, b, b). Schröder van der Kolk, 
Bidder, and others, (as stated above,) consider the anterior roots as arising without 
' exception from the cells of the anterior cornua. With this view I cannot agree, for, 
as it must be acknowledged that at present the fibres we are able to trace with any 
certainty from cells to the anterior roots are rather the exceptions than the rule, this 
theory is evidently more the result of inference than of direct observation. On the 
other hand, we have the fact, the evidence of which I shall discuss further on, that 
part of the anterior roots are direct continuations of the posterior roots without the 
intervention in the cord of any cells. + | 
* Philos. Trans., 1859, p. 457; also *J. L. Clarke on the Anatomy of the Spinal Cord," Beale's Archives, 
1858, Pt. III. p. 207. 
f Schilling maintains that “fibres from the posterior roots never enter the anterior cornu.” This is entirely 
opposed to the observations of Stilling and Clarke, as well as my own. 
