550 
cerebrum, and uncovered by it. Tiedemann* has, however, made an 
exception in favour of the seal, in which animal he says posterior 
lobes occur, although shorter than in the Simise. Cuvier - !* also re- 
cognises the exceptional arrangement in the seal, and places along 
with it the otter and the dolphins. RetziusJ states, that in the 
mammalia lower than man, posterior lobes are found only in the 
apes, and that rudiments only are met with in the Cetacea and 
seals. 
In the course of a series of observations which I have been 
making for some time back, on the crania of different mammals, 
my attention has been especially directed to the relative positions of 
the cerebrum and cerebellum. These observations have led me to 
come to the conclusion, that considerable misconception exists as to 
the relations of the two chief divisions of the encephalon. 
If, relying on the published drawings, one may give an opinion of 
the method of examination of the brain which has been mostly 
adopted by anatomists, it would appear that the relation of the con- 
stituent parts of the brain has been determined after its removal 
from the cranial cavity, and with its base resting on a flat sur- 
face, such as a plate. By a procedure of this kind a very incorrect 
estimate is formed, for great displacement of parts ensues, especially in 
the lower mammals. The cerebrum slips forwards, the cerebellum 
backwards. The medulla, instead of being more or less oblique, is 
placed horizontally, and causes the cerebellum to be tilted upwards. 
The arched form of the base is almost entirely destroyed. The displace- 
ment is still greater if, at the same time, the membranes are re- 
moved^ The observations which I have conducted have been, for 
the most part, made without removing the brain from the cavity of 
the skull. My dissections have been performed chiefly after two 
methods : ls£, By making vertical sections through both skull and 
brain, immediately on one side of the middle line, so as to preserve 
uninjured the falx cerebri, and the whole of one lateral half of the 
organ ; 2d, By carefully removing with the bone-forceps the pos- 
* leones Cerebri Simiarum, p. 48. 
t Le 5 ons d’Anatomie Comparee, vol. iii., 1845. 
J Muller’s Archivs, 1846, p. 154. 
§ Mr Marshall, in his description of the brain of a young chimpanzee (Nat. 
Hist. Rev., vol. i. p. 298), has pointed out very clearly, in the brain of that 
animal, the changes which ensued after removal from the skull, and immersion 
for a time in spirit. 
