190 
ME. W. H. ELOWER ON THE POSTERIOR LOBES 
Order QUADRUMANA. 
Family 1. CatarrMna. 
Orang-Utang {Pithecus satyrus ). — The brain of a young female of this species, which 
died in the Gardens of the Zoological Society, May 1850, is preserved in the Museum of 
the Middlesex Hospital. Although this specimen has retained its form and general 
characters unusually well, I do not propose to give any detailed account of it, being 
unwilling to multiply the too numerous imperfect descriptions which akeady exist of 
the cerebral anatomy of this animal — imperfect inasmuch as they are mostly taken 
from specimens the form of which has been more or less altered by preservation in 
spirit. A general flattening of the cerebral mass, contraction of the hemispheres, with 
loss of characteristic outline, obliteration of distinction between white and grey sub- 
stance, and adherence of contiguous walls of sulci and cavities, render such brains iU 
adapted for the successful study either of the external characters or internal structure. 
The following points relating to the posterior lobes of the cerebrum are, however, to 
be noted in this specimen. On looking directly down upon the centre of the upper 
surface of the brain, no part of the cerebellum is visible, either laterally or posteriorly. 
When wewed from one side, the posterior lobes are seen to project exactly as far back- 
wards as completely to cover the cerebellum, but not to extend beyond it. But an 
examination of the interior of the cranium from which the brain was taken, shows that 
the shrinking of the hemispheres has reduced their dimensions in this dkection. It is 
therefore perfectly evident that the posterior lobes of the cerebrum, according to any 
deflnition taken from external characters, exist in a very well-developed condition, 
although not prolonged backwards to quite so great an extent as they usually are ui 
the human brain. 
To examine the interior, the upper portions of the hemispheres were removed to the 
level of the inferior surface of the corpus callosum, and then further portions were care- 
fully dissected away so as to expose the lateral ventricles with their three cornua. The 
general form of the cavity presents almost the exact counterpart of that in the human 
subject. The posterior cornu extends as far backwards as an average example in Man, 
being -fths of an inch long, and its apex being but fths of an inch ( = |^th of the entire 
length of the hemisphere) from the surface of the posterior lobe. The projection of the 
hippocampus minor bears comparison with a very well-developed specimen of this 
structure as met with in the human brain. Its length is fths of an inch, its breadth at 
the base -^ths of an inch. The eminentia collateralis is more prominent than in many 
human brains. The hippocampus major has no distinct digital marks, but the convex 
border of its expanded termination has a slightly nodulated appearance. There is a 
complete correspondence of form in the ventricles of the two hemispheres, the posterior 
cornu extending backwards to a similar extent in both. 
As it seemed desirable to possess an exact means of estimating the length of the 
posterior lobes in different animals by a criterion derived from internal structure, I have 
