340 THE LUMBAR ENLARGEMENT OF THE SPINAL CORD. 
The connection of the posterior roots with the cells of the posterior cornu has never 
been determined so satisfactorily; and, as considerable difference of opinion exists 
among authors, I shall compare somewhat at length the. principal views which have . 
been maintained. 
R. Wagner* divides the posterior roots into three classes, of which the first pass 
directly upwards to the brain, without entering the gray substance; the second enter 
the gray substance and unite with nerve-cells, either collected in groups or strewn sin- 
gly through the posterior cornua; the third class of fibres, very considerable in number, 
do not contribute to sensation, but pass to the large cells in the anterior cornua from 
which the anterior roots arise. Schröder van der Kolk agrees with Wagner, that the 
true sensitive fibres ascend directly to the brain without entering the gray substance, 
the only fibres from the posterior roots which enter the gray substance being, according 
to him, the reflex, i. e. transverse, and these he infers may enter cells. Stilling 
states that he has “never yet succeeded in observing the direct communication of a 
primitive nerve-fibre of the posterior roots with a nerve-cell of the gray substance, 
although he maintains this relation between them." Clarke§ describes and figures 
(Pl XIX. Fig. 1) cells of the gelatinous substance as continuous by their processes 
with the posterior roots; of the cells constituting the posterior vesicular columns he 
says, * When the posterior roots of the nerves are traced inwards, they are found to be 
most intimately connected with all parts of the posterior vesicular columns." (p. 445.) 
He also states, that “the processes of these cells (of the posterior vesicular columns) 
are prolonged in every direction, — transversely they are continuous on the one hand 
with the posterior roots of the nerves, and on the other hand with the posterior com- 
missure."| These statements are illustrated in the Philosophical Transactions for 1859 
by very accurate figures, Pl. XIX. being certainly the only correct delineation of the pos- 
terior cornu hitherto published. Figs. 6 and 7 of my own drawings illustrate the con- 
nections which are seen to exist between cells of the posterior cornu and the nerve roots. 
In the longitudinal section (Fig. 6), fibres from the cells will be seen to be continuous 
with the transverse bundles b, b, and the ascending bundles c, c, which are direct con- 
tinuations of the posterior roots, being shown in the figure soon after their passage 
through the substantia gelatinosa, the line d d marking very nearly the boundary 
between the more opaque portion of the caput and the cervix cornu. Fig. 7, from a 
transverse section, represents the manner in which the cells are connected with the 
* Neurolog. Untersuch., (Góttingen, 1854,) p. 66. T Op. cit., p. 47. 
i Neue Untersuch., p. 929. $ Philos. Trans., Pt. L, 1859. 
|| J. L. Clarke on the Anatomy of the Spinal Cord, Beale's Archives, No. III. 
