112 J. B. JOHNSTON, 
right ganglion are not impregnated in my preparations, the large 
dendrites are often impregnated and the origin of the fine fibres 
from these dendrites is very clearly visible. The coarser fibres seem 
to comport themselves as do those on the left side. I conclude, 
therefore, that the coarser and finer fibres are all of the same 
character, all arising from one kind of cells in the ganglia. I see 
no explanation for the peculiar arrangement of fibres in the right 
_ ganglion except its larger size. 
The tracts which come from the fore brain to the ganglia hab- 
enulae have been described in my previous paper under the name 
of the tractus olfacto- and cortico-habenularis. For reasons stated 
elsewhere (page 235), I now drop the name _ tractus cortico-ha- 
benularis. According to my previous description (98a, p. 235) these 
tracts enter the ganglia habenulae, cross to the opposite side and 
end in relation with the cells described above. There is reason for 
thinking, however, that not all these fibres cross to the opposite 
side. The fibre layer in the right ganglion is much larger than in 
the left, and in haematoxylin sections the right tractus olfacto-ha- 
benularis appears larger than the left. It seems necessary to sup- 
pose that more than than half of the fibres of the two tracts end 
in the right ganglion. GOLGI preparations give little help on this 
point, but in two series the right tract seems to divide as it enters 
the ganglion, one bundle going to the commissure while the other 
runs directly into the central part of the right ganglion. This 
would explain the larger size of the right ganglion and of the right 
bundle of MEYNERT. 
b) Thalamus. 
1. Dorso-cephalic Part of Thalamus (Fig. K). 
The dorsal part of the thalamus cephalad from the ganglia 
habenulae has proved one of the most complicated and difficult 
regions in the whole brain. It consists of a mass of cells among 
which run the tractus olfacto-habenularis and another tract which I 
shall call the common longitudinal bundle of this region. In frontal 
sections stained with haematoxylin the mass of cells appears as a 
cap surmounting the thalamus. This cell mass extends cephalad on 
the outer surface beneath the caudal part of the epistriatum. Caudad 
it extends on the inner. surface to become continuous with the 
central grey matter. The cells of the whole region present great 
