408 THE SPECIAL SENSES. 



In experiments made upon dog-fish Lee* found that when the 

 animal is rotated in the planes of the several canals there are definite 

 movements of the eyes and fins for each plane of rotation. More- 

 over, since mechanical stimulation of an ampulla causes move- 

 ments of the eyes and fins identical with those resulting from 

 rotation of the animal in the plane of that canal, it follows as a 

 probable conclusion that the sense cells in each ampulla are 

 actually stimulated by movements in the plane of its canal. In 

 man also it may be shown that the sensory endings in the several 

 ampullae are probably stimulated by rotation of the head in the 

 corresponding planes, and that these stimulations set up definite 

 reactions that vary according to the ampulla most affected. Cer- 

 tain of these reactions have been found useful in otological prac- 

 tice, especially those designated as the "Barany tests." f If f r 

 example, a person is rotated in a turning chair for a number of 

 times in one direction, say, to the right, and then suddenly stopped, 

 the following reactions may be noted if the head has been so held 

 that the rotation is in the plane of the horizontal canals. There is a 

 nystagmus or jerking movement of the eyeballs, and a false sensa- 

 tion, vertigo, of movement to the left. In addition, there is a 

 certain inaccuracy in movements made with the eyes closed, which 

 is brought out in the "pointing error" test or "past pointing." To 

 make this test the hand is stretched out so that the finger points 

 to or touches some object, e. g., the finger of the observer. 

 With the eyes closed the individual raises his extended arm to a 

 Vertical position and then lowers it again to touch the same point. 

 Before rotation this movement is accurately made, but after rota- 

 tion he errs to one side or the other. If rotated horizontally to the 

 right he will err or "past point" to the right. The vertigo, nystag- 

 mus, and "past pointing" will continue for a number of seconds 

 (twenty to twenty-five) in a normal person with diminishing in- 

 tensity. By giving the head different positions it is possible to 

 rotate it in planes (sagittal, frontal) which involve the vertical 

 canals, and the character of the responses obtained may be used 

 to determine whether or not the sense-cells in these canals are 

 functioning normally. 



Effect of Section of the Ampullary or the Acoustic Nerve. 

 Many of the older and newer observers have cut one or both of the 

 acoustic nerves or destroyed the entire labyrinth on one or both 

 sides. The effects described vary somewhat with the animals used, 

 but, in general, section of the nerve on one side is followed by 



* Lee, "Journal of Physiology," 15, 328, 1903. 



t Barany, "British Medical Journal," 1910, 2, 1245; also "Transactions of 

 International Congress of Medicine," London, 1913; also Jones and Fisher, 

 "Annals of Otology, Rhinology, and Laryngology," March, 1917. 



