I. the Horizontal Canals.* the Journal of General Physiology

It has long been known that the eye movements resulting from the stimulation of any ampulla correspond very closely to the compensatory movements brought about by rotation of the animal in the plane of the semicircular canal of which that ampulla forms a part. In the dogfish this correspondence has been shown by the work of Lee (1894) and of one of us (Maxwell, 1910) to be very exact. It seems desirable to determine just what part each of the six extrinsic muscles of the eyeball takes in the response to stimulation of a single ampulla. The methods of our experiments were as follows: The dogfish was tied down on the operating board and its respiratory needs were provided for in the usual way; namely, by bringing a stream of aerated sea water into its mouth through a rubber tube from an elevated receptacle. The desired muscles were isolated and the bulb of the eye enucleated by a method essentially similar to that of Bartels (1911). On account of the delicacy of the muscles we have not attempted to tie threads to them directly but instead we have in each case cut out that portion of the sdera which includes the insertion of the muscle, and have then with a small surgical needle passed the thread through this bit of sclera and tied it. The writing levers used were very light and were right-angled so that a horizontal pull caused * The expenses of this research were defrayed in part by a grant from the