The position of the head after experimental removal of the otic labyrinth

Abstract

In the vertebrates usually employed in the physiological laboratory, unilateral destruction of the otic labyrinth is immediately followed by a permanent torsion of the head to the injured side. 1 In a series of experiments on cats, I have found that this posture is associated with diminished tonus in the cervical musculature on the side of the lesion. Although this investigation is as yet incomplete, it is considered desirable to report the following facts.

As a means of determining the effect of impaired tonus on torsion of the head, apart from that arising from destruction of the labyrinth, the following procedure was adopted:

1. UNILATERAL SECTION OF THE DORSAL ROOTS OF THE CERVICAL NERVES.

Accompanying the impairment of muscular tonus occasioned by this procedure, there is torsion of the head to the side of the injury. This torsion can only be attributed to the unbalanced activity of the neck muscles on the intact side. It is to be noted that the character of torsion following section of the dorsal roots of the cervical nerves does not differ greatly from that seen after unilateral removal of the labyrinth. In a dog, which has not yet come to autopsy, section of the dorsal roots was followed by torsion of the head to the side away from the lesion.

The remaining series illustrate the torsional effect of various combined lesions.

As stated before, unilateral removal of the labyrinth is followed by torsion of the head to the side of the injury. Upon subsequent section of the dorsal roots of the cervical nerves on the opposite side this torsion is greatly reduced and in some cases entirely disappears. Reversal in the order of the experiment does not affect the end result; the torsion resulting from the first procedure is always decreased or abolished by the second.