Bauhaus-Universität Weimar

gives rise to phenomena which seem to indicate a disturbance in the 
equilibrium between forces opposed to each other in the two sides of 
the brain. These phenomena form a class of a quite peculiar character. 
A certain part of the brain being divided, the action of the correspond¬ 
ing part of the other side becomes exaggerated. A vertical section of 
the pons Varolii on one side causes the animal to make a number of 
revolutions towards the same side; and this motion is arrested by di¬ 
viding the pons on the other side. M. Hertwig confirms the result of 
M. Magendie’s experiments, as to the rolling motion of the animal ex¬ 
cited by division of the pons on one side; and states, moreover, that the 
eyes were turned from their ordinary position, one upwards, the other 
downwards. A transverse section of the pons being made, the dog 
could stand, but could not advance a step without falling; voluntary 
movements could still be performed, and sensation was perfect. 
Division of the crura cerebelli (processus ad pont cm) likewise in M. 
Magendie’s experiments caused the animal to roll upon its axis towards 
the side on which the wound was inflicted; performing sometimes as 
many as sixty revolutions in a minute; and M. Magendie states that he 
has known them continue for a week without intermission. 
After the removal of both corpora striata, the animals manifested an 
irresistible impulse to dart forwards, even when vision was lost. 
Magendie has likewise observed that injuries of the cerebellum in 
Mammalia and birds cause a tendency to the performance of retrograde 
movements. He observed the same phenomenon after wounds had 
been inflicted on the medulla oblongata: pigeons, in which he had 
thrust a needle into that part of the encephalon, were observed by him 
for more than a month to walk backwards, never forwards; and he 
states that they actually flew backwards. 
M. Magendie has observed, lastly, that certain kinds of injury to the 
medulla oblongata are followed by the animals moving in a circle, as on 
a riding course. He performed the experiment in a rabbit three or four 
months old; he exposed the fourth ventricle, raised the cerebellum, and 
then made a perpendicular section into the floor of the ventricle at the 
distance of H to If of a line from the mesial line: when the section 
was made on the right side, the animal turned towards the right; when 
on the left, it turned towards the left. 
From the above important facts M. Magendie infers the existence in 
the brain of certain impulses by which the animal is necessitated to 
move in certain directions; by one forwards, by another backwards, by 
a third to the right, and by a fourth to the left: the detail of these move¬ 
ments he supposed to be directed by volition; and he imagines that in 
the normal state of the body the different impulses balance each other. 
Whether this explanation of the phenomena be the correct one, cannot 
in the present state of our knowledge be determined. It may easily be 
conceived that an animal might be impelled to such movements, if from 
the nature of the injury to the brain a certain motion of the nervous 
principle in one direction should take place in it, giving him the sensa¬ 
tion of giddiness,—that is to say, of surrounding objects, or of his own 
body, moving round,—when he would endeavour to resist this apparent 
movement, or would follow it.


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