732 
P. L. B. formation bifurcate, one limb ascending to the oculomotor 
nuclei and the nue. of the posterior commissure, the other passing 
down to the cord. 
The descending bundle has its origin exclusively, so it appears, 
in the nuc. commissurae posterioris (VAN GEHUCHTEN, PRosst) and 
can be traced as far as the homolateral abducens nucleus. The oral and 
distal final stations of both coordinating bundles are therefore found 
in the same level, a detail with seems particularly inviting to study 
here the physiology of the bundle as a common final path (SHER- 
RINGTON). For the study of the mechanism of the circus and rolling- 
movements undoubtedly labyrinth- and neck-reflexes described by 
Macnus and Dr. Kinyn’') as well as Baranyi’s experiments ®) have 
to be considered. 
As to the function it can be hardly considered accidental, that 
in my experiments the animals with ascending degeneration in the 
P. L. B., on one side (eg. on the right side) performed circus- 
movement to the other side, to the left; whereas the animals with 
a (from the Nuc. comm. post) descending degeneration e.g. on the 
right side, did their manege-movements to the diseased side. Progst’s 
law *) that “a hemisection of the brainstem anterior to the red 
nue. caused maneze-movements to the diseased side; a hemisection 
caudal to the red nucleus to the healthy side’, seems therefore, 
“well founded, but with this important restriction, that the nue. com- 
missurae posterioris and not the red nue. is the origin of the commis- 
suro-medullary bundle, and that not hemisection, but a simple lesion 
of one longitudinal bundle will suffice, to cause the circusmovements. 
By comparison with a number of other series and subtraction 
of the phenomena during life, it can be proved, that lesion of the 
great descending tracts (pyramidal, rubro-spinal, tecto-bulbar, vesti- 
bulospinal, and ponto-spinal tracts), of the most important ascending 
systems (Gowers’s and Fecusie’s tract) the lemniscus and cerehello- 
rubral tracts have nothing to do with this function. [ am not in a 
condition to deny nor to affirm CraRrKE and Horsny’s supposition *), 
that the ponto-cerebellar connections should have to do with the 
“mouvement de manege” but I do think as long as there is no proof 
forthcoming, regarding a centre for equilibration in the temporal 
lobes, that after these experiments there is no need to fall back upon 
any such conjecture. 
1) Archiv. f. d. gesammte physologie, 1912. Bd. 145. S. 455. 
2) Neurologischer Centrallblatt. 1912. 
8) Loc. cit. p. 41. 
+) Brain 1905 
