504 ON THE BRAIN OF ATELES PANISCUS 
its termination); and it is,as in Mar, separated from the dentate 
sulcus by the narrow prolongation of the callosal gyrus downwards 
into the temporal lobe, + Lastly, the collateral sulcus, 2 2 x, is 
traceable—though interrupted at intervals—through the same extent, 
as in Man; and of the three parts into which it is broken, the 
posterior is continued back even further than in him, and passes a 
little on to the outer and posterior face of the hemisphere. The 
greater proportional width of the uncinate gyrus, contained between 
the calcarine and dentate sulci above, and the collateral sulcus below, 
is marked in A‘¢eles. The transverse sections (fig. 1. A’, B’, &c.) are 
no less strictly comparable to those yielded by the human brain, the 
chief differences being that, throughout the greater part of its length, 
the calcarine sulcus possesses the bifurcated outer extremity which its 
posterior part only presents in Man; and that the collateral sulcus is 
smaller and further out in proportion, and hence the uncinate gyrus 
is larger. 
As tothe hippocampus minor, the transverse sections (fig. 1) 
clearly show how much larger it is, proportionally, in Aze/es than in 
Man; while the horizontal section (Pl. XXIX. [Plate 36] fig. 5) 
exhibits its exact correspondence with the definition quoted above— 
viz. “an elevation of the inner wall of the posterior cornu of the 
jJateral ventricle, which is convex outwards and forwards ;” and, as 
might be expected from the transverse section, it shows the larger 
proportional size and greater outward convexity of the Monkey’s 
hippocampus minor. 
The eminentia collateralis, on the other hand, is far less developed 
in Azefes than in the particular human brain whence the sections are 
taken; but it is quite distinctly visible at the junction of the 
posterior and descending cornua. The floors of both these cornua, 
however, are so narrow, that the eminentia can hardly be said to be 
continued into them, as it sometimes is into the posterior cornu, and 
almost always is into the descending cornu, in the human brain. 
Thus, in exact contradiction of what has been affirmed, it is the 
hippocampus minor which zs developed, and the continuation of the 
eminentia collateralis backwards which is ot developed in the 
Monkey. 
The sulci and gyri of the outer surface of the cerebral hemispheres 
present in Adeles paniscus the same essential arrangement as in the 
Ateles belzebuth, described and figured by M. Gratiolet. Dividing the 
hemisphere into five lobes (frontal, parietal, median, temporal and 
occipital) the median (insula—Island of Reil) hidden between the lips 
of the Sylvian fissure, is a mere smooth convex projection, wider 
