l6o BIOLOGICAL LECTURES. 



conscious of this fact the moment liis eyes I'est upon some- 

 thing which enables liim to orient himself, and yet tliis normal 

 individual has six organs in his head which are there for 

 the special jnu-pose of controlling of his mox'ements in s}xice, 

 so say the physiologists. His two eyes are of more service to 

 him than are his six canals.^ 



It may be objected that the canals are not intended to take 

 cognizance of such minute changes in position in space as are 

 involved in swimming around in a circle; but if they cannot 

 perceive such changes of position when swimming, how can 

 they perceive them when on a rotating table {e.g., Crum. 

 Brown's experiment). It would be a great service to determine 

 the minimum amount of angular motion of which the canals 

 can take cognizance, in order that we may know liow much to 

 expect of our ear canals in this wa)'. 



It may be objected that the man in tlie water on his back is 

 in an unusual position and consequently his canals do not work 

 with sufficient delicacy on account of the unaccustomed 

 pressure, etc. But it is a necessary consequence of the 

 assumption that the canals are special organs of equilibrium, 

 that they should work in any position; otherwise wliat were 

 the use of them } Otiier organs of specific function work in 

 all positions of the body. The eyes see, tlie nose smells, tlie 

 ears hear, the brain thinks, the heart beats, and so on ad 

 infijiituDi, all except the ear canals, whose special work is to 

 cognize just such unusual si)atial conditions, and according to 

 the hypothesis, the only organs iu the bod\' having this 

 function, — they fail of their function when most needed. In 

 the experiment with the rotating table the canals are subject 

 to even a severer test of \ery small angular motion and are 

 supposed to be able to operate very precisely, in some cases. 



' Kxperimental rides on the great Ferris wheel at Chicago during the Columbian 

 Exposition proved that a perception of the direction of the motion of one's body 

 in space was impossil)le unless one made use of the eyes. I found that the 

 upward motion could not be detected by the ears alone. Without the evidence 

 of one's eyes one seemed to be standing still upon a trembling platform, and the 

 while was really making a great circle through the air in a geotropically oriented 

 position. It is notorious that balloonists have difficulty in determining whether 

 they are moving upward or in any other direction when sight is hindered, and 

 that it is impossible to detect motion in the midst of a cloud. 



