450 Ben J. C. Gruenherg 



In 1878 von Cyon rejected both the static and the dynamic 

 theories of the workings of the semicircular canals. After draw- 

 ing off the endolymph and replacing it with gelatin, and after the 

 introduction of pieces of laminaria into the canals, thus producing 

 great changes in pressure, there were none of the disturbances of 

 equilibrium that had been observed by Flourens as resulting from 

 divisions ot the canals. Without advancing any other explana- 

 tion of how these peripheral organs are excited, von Cyon main- 

 tained that the canals assist but indirectly in giving the organism 

 a knowledge of space relations; the sensations in the canals set 

 up reflexes in the eye muscles, and it is from the sensations of the 

 eye muscles and the retinal images that the notion of spatial rela- 

 tions of the head and of the body are obtained. 



In 1883 Sewall ('83) from experiments on skates and sharks 

 concluded that the results were not sufficient to warrant the opin- 

 ion that the semicircular canals are the organs of equilibration 



3 THEORETICAL OBJECTIONS TO THE SEMICIRCULAR CANAL 



HYPOTHESIS 



Whatever the real manner of operation of the semicircular canals 

 may be, there have appeared certain theoretical objections to 

 Goltz's static theory as well as to the various dynamic theories; 

 these explanations seem to be out of harmony with the observed 

 fact that the responses of the frog's head to rotation are not coordi- 

 nated w^ith the position of the animal in relation to the axis of rota- 

 tion. Thus, in Fig. i, a frog in anv one of the four positions on 

 the turntable, will always turn his head to the left if the table is 

 turned to the right (clockwise), and vice versa, as indicated by the 

 dotted outlines and the peripheral arrows. The action of gravity, 

 or acceleration, in relation to the frog, or whatever dynamic prin- 

 ciple it may be that does act, seems to work in a different direction 

 in each of the four cases. The special sense of the action in each 

 case is indicated in Fig. i by a small arrow. In other words, the 

 animal responds uniformly t© what is apparently a variety of stim- 

 uli; the stimuli in these cases are the same in kind and in degree, 

 but differ in sense or direction, or incidence in the animal's body.. 



