624
THE CEREBELLUM.
lesion does not abolish the motion of the iris,—on the contrary, that
these motions sometimes continue; 3. that by removing a larger portion
of the optic lobe, or completely extirpating it, vision, as well as the con¬
tractile power of the iris, is completely destroyed; 4. that mutilation of
the optic lobe has nearly the same effect on the eye as injury to the
optic nerve; 5. that the muscular weakness of the opposite side of the
body, produced by the mutilation of one optic lobe, is only temporary;
6. that the infliction of this injury on one side of the body, causes the
animal to move round on its axis, as if giddy; 7. that no other effect
than those mentioned follow the mutilation of the corpora quadri-
gemina,—thus, for example, that no disturbance of memory or con¬
sciousness is produced.
The only point in which the observations of this experimenter differ
from those of M. Flourens, has reference to the convulsions produced
by injury to the optic lobes, which, in M. Hertwig’s experiments, never
ensued. The opposite result obtained by M. Flourens was perhaps due
to his incision being carried too deeply.
V. Of the Cerebellum.
The functions of the cerebellum have been made the subject of in¬
teresting experiments by Rolando, Flourens, Magendie, Schoeps, and
Hertwig.
M. Rolando constantly observed that the diminution of the move¬
ments was in a direct ratio with the lesion of the cerebellum; that stupor
was never produced, nor the sensibility of any part of the body im¬
paired; but that the power of the muscular movements was lost. The
animals kept their eyes open, and regarded surrounding objects, but in
vain endeavoured to execute any of the movement necessary for loco¬
motion. An animal in which one side of the cerebellum had been re¬
moved, fell upon the same side, not being able to support itself upon the
leg of that side. These results induced Rolando to adopt a supposition
quite incapable of proof, namely, that the cerebellum is the organ
destined for the generation of the nervous principle, which he compared
with electricity; and that the alternate layers of white and grey sub¬
stance of the cerebellum act, as Reil also imagined, in the way of a
galvanic pile.
The experiments of M. Flourens (Loc. citât, pp. 18 and 36,) are
more lucid and more decisive in their results. He found that the ani¬
mals evinced no signs of sensibility in the cerebellum while it was being
removed. He extirpated the cerebellum in birds by successive layers;
feebleness and want of harmony of the movements were the conse¬
quence. When he had reached the middle layers, the animals became
restless without being convulsed; their movements were violent and
irregular, but their sight and hearing were perfect. By the time that
the last portion of the organ was cut away, the animals had entirely
lost the powers of springing, flying, walking, standing, and preserving
their equilibrium. When an animal in this state was laid upon the
back, it could not recover its former posture; but it fluttered its wings,
and did not lie in a state of stupor; it saw the blow which threatened
it, and endeavoured to avoid it. Volition, sensation, and memory,