108 J. B. JOHNSTON, 
I have seen. They always run ventro-mesad, ventral to the fasci- 
culus, and cross the middle line in the commissura ansulata. They 
are lost to view in the ventral column of the opposite side. In its 
caudal part this nucleus seems to merge with those cells in the 
tuberculum acusticum which border on the cavity, the Acusticus- 
zellen of GORONOWITSCH. It is difficult or impossible to distinguish 
these from one another or either from the commissural cells of the 
medulla (cf. page 81, above). I have mentioned in a previous paper 
(98a) the fact that both the bundles of MEYNERT and a bundle 
which comes up from the medulla end in this nucleus. The detailed 
description of these bundles and their manner of ending appears 
below (page 130). 
Cells of the corpus interpedunculare. — Among the 
decussating fibres of MEYNERT’s bundles and caudal to the cephalic 
thick portion of the commissura ansulata there are a few very small 
cells with small and poorly branched dendrites. The neurites start 
from the cells in a dorsal direction. I have found only three or 
four cells in this region in two GOLGI series, and haematoxylin 
sections show but very few cells present here. 
2. Nuclei of the III and IV Nerves. 
The impregnation of these nuclei is so faulty in my preparations 
that it has not been possible to trace the neurites from the cells 
into the motor roots in any case. I have found a group of motor 
cells at about the cephalic border of the commissura ansulata to 
which I have traced the III nerve by means of its medullary sheaths. 
The nucleus of the IV nerve I have not recognized with certainty, 
probably, because it has few cells, the nerve itself being very small. 
C. The ’tween Brain. 
a) Epithalamus. 
1. The Epiphysis and Pineal Gland. 
Immediately cephalad from the posterior commissure the cavity 
of the ’tween brain is produced dorsally into the epiphysial sac and 
from this the pineal stalk extends upward and forward over the 
paraphysis. The dorsal decussation of the tectum has its cephalic 
limit at the epiphysial sac. However there continues forward from 
the dorsal decussation and apparently continuous with it, a thin 
