0 The American Naturalist. [December, 
the posterior white columns, and a portion into the grey matter of the 
posterior horn. Of the former, Singer’s view is supported by others, 
and seems correct, viz.: That these fibres form long paths direct to 
the medulla oblongata, where they end in the nuclei of the posterior 
columns. From here continuing fibres go to the cerebellum an 
elsewhere ; but the work of Edinger, Flechsig, and Meynert has proved 
that a great number of the continuing fibres cross to the opposite side, 
and as a part of the fillet go anteriorly, and end in the corpora quad- 
rigemina. ‘The latter portion of the posterior root fibres mentioned 
above, those entering the posterior cornu, disappear in its grey mat- 
ter, but the connections of this are difficult to follow. Beyond the 
fact that fibres may be traced laterally from Clarke’s column through 
the lateral white columns to the direct cerebellar tract, and thence 
anteriorly, much confusion exists as to the fate of the other posterior 
cornu fibres. 
Edinger’ has employed embryological combined with comparative 
anatomical methods, beginning with Anguis fragilis, and confirming 
his results on other reptiles, fishes, amphibians, and mammals, From 
the nucleus of each sensory cranial nerve (V., IX., X.) he traces 
a bundle of fibres across in the medulla and anteriorly as a part of the 
fillet to the corpora quadrigemina. The strie acustice, from the 
nucleus of the eighth, take the same course (Monakow). Edinger 
calls this connection the ‘‘central sensory path” of the cranial 
nerves, and searches for an analogous tract in connection with the 
spinal nerves. In various forms he finds this in bundles of fibres 
emerging from the grey matter of the posterior cornu, crossing in the 
anterior commissure to the antero-lateral white columns, thence 
ascending, joining the fillet, and ending in the mid-brain. The 
existence of such a ‘central sensory path” of the spinal nerves is 
confirmed by physiological experiment, by embryology, e.g., His, and 
by pathological anatomy, e.g., Auerbach and Rossolymo have found 
this path degenerated after destruction of the posterior horns. Hence 
we seem to be in a fair way to understand the central connections of 
the posterior root fibres. Leaving out of account those going to the 
cerebellum, and some few others not well understood, there are two 
groups. In one the fibres enter the posterior columns, ascend, pass 
through the ganglia of those columns, cross, and as a part of the fillet 
go to the corpora quadrigemina. In the other the fibres join the grey 
matter of the posterior cornu, cross in the anterior commissure, 
ascend in the antero-lateral white columns, and as another part of 
the fillet go also to the corpora quadrigemina. 
1 Deutsche Med. Wochenschrift, May, 189o, No. 20, P- 421. 
