Abstract
The peculiar method of progression in serpents 1 and the widely different modes of progression in lizards, snakes and turtles 2 have attracted attention to the relation of the semi-circular canals to the processes of progression and maintenance of equilibrium in these forms.
The general results of labyrinthine extirpation in all these forms are similar to the results observed in other vertebrate types. There is, in the turtle, torsion of the head to the injured side, permanent deviation of the eyes and a tendency to crawl or swim toward the injured side, when the lesion is unilateral. The body on the uninjured side may be raised higher than on the injured side.
After bilateral operation, there are coarse wide tremors of the head which seriously interfere with grasping food. The gait on land is not markedly affected permanently, and there is no permanent torsion of the head to either side. The head may, however, be displaced directly upward and backwards in the first few days following extirpation. Swimming is a matter of great difficulty. When the turtle moves slowly, progress is fairly good, but agitation or hurry upset coördination and extreme disorientation results. The animal's reactions are not biologically adequate (Edinger).
It may be shown in turtles and snakes particularly that the otic labyrinth is a great proprioceptive organ for the head segment (Sherrington). The rô1e of the labyrinth in the maintenance of equilibrium rests primarily upon its relation to the head, and only secondarily upon its relation to the body. It may be shown that under certain conditions, the head is the only part affected.
Get full access to this article
View all access options for this article.