Abstract
It is of some interest, in view of the tendency in some quarters to insist upon the essential similarity of the effects of lesions of the labyrinth and of the cerebellum, to ascertain whether this supposed constancy of relationship obtains in animals with a relatively small cerebellum. It may be mentioned that, anatomically, the floor of the mid brain (the pons) and that portion of the roof represented by the vermis cerebelli are phylogenetically old. The lateral lobes of the cerebellum are new developments. The cerebellum of turtles is represented by the vermis. The cerebellum in the genera of turtles used for experiment—–Nanemys and Chrysemys—–is smaller than in the sea turtles.
We have already pointed out the fact that there is a great uniformity in the effects of labyrinthine lesions in all animals so far studied 1 and that the effects in the turtle are much the same as in other animals. 2
Ablation of the cerebellum in the turtle does not give rise to the same train of symptoms that is observed after labyrinthine extirpation. We find, in agreement with Fano, 3 that the righting reaction is not abolished by ablation of the cerebellum. There was a small, scarcely noticeable, disturbance of coördination in swimming, manifested most clearly in a slight awkardness in approaching the side of the tank. Occasionally, lack of precision of limb movements on the injured side was observed after unilateral operations. One other symptom was that the animal was rarely or never seen to swim deep in the water after cerebellar removal. Our observations substantiate those of Fano, Bickel 4 and Sergi, 5 whose experiments were done on different genera of turtles.
The results on turtles are in substantial agreement also with those of Steiner, 6 Loeb, 7 Bethe 8 and Corso, 9 who report no noticeable motor disturbances in sharks (Scyllium) after cerebellar ablation.
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