ae OLIVER S. STRONG 
In the region of the inferior colliculus (fig. 18) the most strik- 
ing feature is the great inequality in the fibers of the pes on the 
two sides. The sectional area of these fibers on the left is just 
about three times the area of those on the right. The fibers 
present on the left but not on the right are, of course, the 
pallio-pontile fibers which terminate in the pontile nuclei. The 
fibers of the right pes would be composed almost entirely of py- 
ramidal fibers and as a matter of fact the area of the right pes is 
not far from that of one of the pyramids below the pons. 
An interesting fact, very apparent in the sections, is that the 
substantia nigra varies pari passu with the pes. The dispro- 
portion between the right and left substantia nigra is nearly, 
though not quite as great as that between the right and left 
pes. This would seem to indicate a close connection, probably 
by collaterals, between the two. This connection, however, 
would not necessarily be only between the pallio-pontile and 
pyramidal fibers and the substantia nigra. At a higher level 
(fig. 19) the discrepancy in size between the right and left pes 
and between the right and left substantia nigra, especially the 
latter, is apparently much less. This would rather point to 
descending fibers which entirely end in the substantia nigra. 
The above-mentioned facts about the right pes, its diminution 
from subthalamic to prepontine region and its practical equality 
in size with the pyramid not only favor the pes containing, at 
the former level, fibers which terminate in the nigra but militate 
against descending fibers in the pes which originate in the nigra. 
In figure 18 the decussation of the superior cerebellar peduncle 
is shown, or rather the crossing of the right peduncular fibers to 
the left side. The portion of the left peduncle here distinguish- 
able is represented by a few uncrossed straggling fibers dorsal to 
the left central tegmental tract. The rest is crossing or has 
already crossed to the right. 
Dorsal to the iter is seen another tangle of fibers in the central 
gray similar in character to that already noted. 
The principal point to be noted in the sections at hand of higher 
levels is the absence, as far could be ascertained, of the right 
nucleus ruber. Owing to a serious gap in the series it could not 
