NERVE-CELLS IN THE MAMMALIAN SPINAL-CORD. 
45 
directly connected with fibres of the posterior roots, and named by him “ Hinter- 
zellen.” It is conceivable that the out-lying cells are really equivalent to cells of the 
dorsal root-ganglion, although placed in an intra-spinal position. If so, they may help 
to explain the observation of Joseph'"' that not all the nerve-fibres of the dorsal root 
degenerate on being cut off from the root-ganglion. Joseph’s observations were, 
however, made on an upper cervical nerve-root. 
If, as according to the view of HENSENf and of Schenk, | the cells of the dorsal 
root-ganglia are nothing else than nerve-cells that originally were a part of the 
cord itself, then the out-lying cells in the root-zone suggest that the posterior vesicular 
column of Clarke may be composed of cells equivalent to those composing the root- 
ganglia, that have, however, retained their original position as a constituent of the 
cord.§ The occurrence of Clarke’s column in the thoracic region would then well 
agree with other features which show that region to present more primitive characters 
than, for instance, the regions of the enlargements. 
group. Freud’s papers on the subject appeared in 1877 and 1878. He designated the large cells into 
which he traced the posterior root-fibres innere Einterzellen. The name aussere Tli'iiterzellen he reserved 
for certain cells, similar, he considered, to the innere Hinterzellen, which he found placed upon fibres of 
the posterior root, between the root-ganglion and the posteinor horn of grey matter of the cord. 
According to Freud, some of the aussere Einterzellen lie at the surface of the cord, upon fibres of the 
posterior rootlets which run for a distance upward along the surface of the spinal cord. Other indi¬ 
viduals of the aussere Einterzellen lie within the cord, upon nerve-fibres of the posterior roots in their 
intra-spinal course. If this nomenclature be transferred to the Mammalian cord, then the cells of the 
posterior vesicular column are the innere Einterzellen of Fetromyzon, and the out-lying cells of the 
posterior root-zone are the intra-spinal set of the aussere Einterzellen. As judged of from Freud’s 
figures of Ammocaetes' cord, the innere Einterzellen do certainly in their position, and fairly in their form 
also, justify Stilling’s view of their identity with Clarke’s vesicular column of the Mammalian cord_ 
The appearance of them in some sections of Ammocoetes' cord, which I have been permitted to examine 
through the kindness of Dr. Gaskell, also bears out in this respect the impression obtained from the 
figures given bjr Freud. That the cells of Clarke’s column are connected on their proximal side with 
the fibres of the cerebellar tract admits of little doubt; as to their distal connections, it may be said that 
two views are current. The one, which has recently been ably supported by Mott (Joe. cR.), is that the 
cells are connected with afferent fibres, fibres of the posterior I’oot. The other (Gaskell, Hill) is that 
Clarke’s column is connected with the efferent fibres of anterior roots. Of these views, the former, I 
think, derives support fi'om the facts observed with regard to out-lying cells in the posterior root-zone 
of the cord; but it is difficult to believe that these out-lying cells, although they appear equivalent to 
members of Clarke’s column, can be at all closely connected with any fibres in the anterior root. Indeed, 
it appears more likely that not only the vesicular group of Clarke, and the out-lying cells of the external 
posterior column, but also the cells described above (p. 43) as occurring in and near the gelatinosa, all 
belong to the afferent system entering by the posterior root.—June 12, 1890.] 
* ‘ Archiv fur Physiologic,’ Du Bois-Reymond, 1888. 
t “Beob. fiber d. Befruchtung u. Entwick. des Kaninch. u. Meerschw.” ‘ Ztschr. f. Anat. u. 
Entw'ickl., vol. I, 1876. 
f “Die Entwick. der Gangl. u. des Lobus olectricus.” ‘Sitz. d. Kais. Akad. zu Wien,’ vol. 74. 
§ Interesting in this connection are the small ganglia intercalaria which, as Htrtl was the first to note, 
occasionally occur on the posterior roots of the human cord, between the main root-ganglia and the cord 
itself. Cf. Hyrtl. 
