NERVOUS CENTRES, (Human Anatomy, Tue Encepnatoy.) 
ment of physiology, that a distinct series of 
nervous fibres is directed to each class of 
actions, those, namely, of sensation and volition, 
and those which are independent of the brain. 
Mr. Grainger was the first who offered a distinct 
solution to the anatomical problem which arose 
out of this hypothesis. Probable as his expla- 
nation appears to be, a candid review of the 
observations which have been hitherto made 
obliges me to state my opinion that the question 
is still sub judice, and that further research is 
“necessary to prove unequivocally that of the 
fibres composing the roots of the nerves, some 
“pass upwards and enter the brain, and others 
do not pass beyond the grey matter of the 
inal cord. And this inquiry demands more 
an ordinary care, for the mind of an observer 
“would be easily biased by so attractive an hy- 
pothesis as that above referred to. 
__ It is not from physiological experiment nor 
from coarse dissections that we can expect a 
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is figure displays well the subdivision of 
the encephalon adopted in this article, 
(After Mayo. ) 
1.—Medulla oblongata. 
Pp, anterior pyramids, 
0, Olivary bodies. 
F r, restiform bodies. 
3 
re proceeding, 
fo however, to the description of 
these portions, 
ie } it will be necessary to take a 
ief review of some general points connected 
vith the entire encephalic mass. 
The size of the encephalon by no means 
661 
solution of this difficult but most important 
problem. We must look to the mrroscopical 
analysis of the anatomical elements of the 
spinal cord, as well as of the encephalon, for 
the most exact results upon all questions con- 
nected with the working of these centres. In 
a subsequent part of the article I shall give an 
account of the present state of our knowledge 
of this most interesting subject, having first 
examined the coarser anatomy of the several 
parts of the encephalon. 
2. Or THe Encepuaton. Gr. eyxePadov or 
syneDaros (ev tn xePaan); Fr. l’ Encephale, le 
cerveau; Germ. das Gehirn ; The Brain.—This 
term is used here in its strictly etymological 
sense to denote that part of the cerebro-spinal 
centre which is contained within the cavity of 
the cranium. Although it forms a great mass, 
continuous throughout, it offers certain very 
obvious subdivisions, which may be more con- 
veniently described separately (fig. 379). Be- 
379. 
2.—Mesocephale— 
¥Y» pons Varolii. 
¢, corpora quadrigemina. 
3.—Cerebellum. 
4,—Cerebrum— 
a, anterior lobe. 
m, middle lobe. 
J, fissura Sylvii. 
5, posterior lobe. 
keeps pace with that of the body. In com- 
paring that of the four classes _ of vertebrate 
animals, we observe a manifest increase of its 
size as compared with the body in the follow- 
ing order, fishes (minimum), reptiles, birds, 
