924 
posterior root-fibres end in the nuclei of Gor and Burpacn, and 
the fibres originating in these nuclei have continued their course 
therein through the decussatio lemnisci — from this is determined 
the intactness of deep sensibility (stereognosia, sense of space, per- 
ception of passive and active motion of the right half of the body). 
It is generally taken for granted that the thin fibres in the marginal 
zone of Lissaugr conduct their impulses into the fibres of the spongiosa 
of the formatio RorLaNpo, and after passing through the substantia 
gelatinosa and the cells of Gierkr are absorbed by the terminal cells, 
adjacent to the substantia gelatinosa. 
The axones of the cells are then thought to cross one another in 
the anterior (and posterior) commissure, and to continue their course 
as tractus spino-thalamicus in the lateral column of the medulla. 
It is just because of experiences similar to the case here described 
that the tractus spinothalamicus has been assumed to be invested 
with the function of conducting the thermal and pain-impulses. 
It is different for the tactile sense. Tactile impulses enter likewise 
into the thin fibres of the zone of Lissaver, but they may pass 
thence immediately into the marginal cells of the spongiosa of the 
formatio RoraNpo, — the zonal cells. Their axones may ascend as 
well through the posterior as through the lateral cords of the uni- 
lateral and the controlateral side, it is even most probable that these 
prolongations are so diffused in the tegmentum of the spinal cord, 
that the conduct of these impulses remains possible as long as even 
a small part of it has been preserved. In the left half of the 
Fig. IV. Scheme of the LissAvER marginal zone and of the substantia RoLanpo 
with the origin of the tractus spino-thalamicus. 
oblongata there is a sufficient number of fibres, both in the lemniscus 
medialis and in the median portions of the formatio reticularis grisea 
