OF THE PONS VAROLII,
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therefore, were not lost, but merely the faculty of combining the actions
of the muscles in groups; and the endeavours of the animal to maintain
its equilibrium were like those of a drunken man. The experiments
afforded the same results when repeated on all classes of animals, and
from them Flourens infers that the cerebellum belongs neither to the
sensitive nor to the intellectual apparatus; and that it is not the source
of voluntary movements, although it belongs to the motor apparatus:
the infliction of wounds on it does not, however, he says, excite convul¬
sions, as when other motor apparatus, such as the spinal cord and me¬
dulla oblongata, are wounded; —but the removal of it destroys the force
of the movements, and the faculty of combining them for the purposes
of locomotion,—the faculty of the co-ordination of the movements. If
this view be correct, the cerebellum must contain a certain mechanism
adapted to the excitement of the combined action of muscles, so that
every disturbance of its structure must destroy the harmony between
this central organ of combined motions, and the groups of muscles with
their nerves. It is also to be remarked, that injury to the cerebellum
always produces its effects on the opposite side of the body.
These observations of Flourens have been confirmed by Hertwig,
who found that the cerebellum itself was insensible; that irritation of
it excited no convulsions; and that though lesion of it interfered with
the combination of movements, the senses and all the other functions
were not thereby affected. Hertwig, however, remarked, that if the
mutilation of the cerebellum had been partial only, its function was
restored. He also found that removal of one side of the cerebellum
affected the-movements of the opposite side of the body.
M. Magendie states that hedgehogs and guinea-pigs, in which he had
extirpated both cerebrum and cerebellum, rubbed their nose with their
paws when vinegar was held to it. He asserts, also, that, when the
wound was inflicted on the cerebellum, the animal made an effort to
advance, but was compelled by an inward force to retrograde. Injury
to the crus cerebelli or processus adpontem, and of the pons itself, upon
one side, always caused the animals to roll over towards that side. The
same effect was produced by every vertical section which involved the
medullary mass lying over the fourth ventricle, but it was seen in the
most marked degree as the result of injury of the crus. Sometimes,
M. Magendie says, the animals made sixty revolutions in a minute, and
he has seen this movement continued for a week without cessation.
These are not convulsive movements, but are voluntarily performed,
as if under the influence of an internal impelling force, or as if the
animals were attacked with vertigo. Division of the second crus cere¬
belli is stated by M. Magendie to restore the equilibrium. Hertwig
also observed in a dog in which the pons Varolii was wounded on the
right side, that similar revolutions of the body towards the same side
were performed, and one eye was turned upwards while the other was
turned downwards. Superficial wounds of the pons were, in Hertwig’s
experiments, attended with moderate pain; he believes each half of the
pons to influence the opposite half of the body. No convulsions were
caused by irritating it.
The restiform bodies belong to the medulla oblongata; injury inflicted
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