Coi/ipx'ii.uitory MrAiofis 453 



ing. "Galvanic dizziness * * * is caused by irritation of the 

 vestibular nerve endings, as galvanic phosphorescence is pro- 

 duced by irritation of the retina." Lee ('93, '94, '98) found the 

 responses to stimulation ot the canals and ampullae such as to 

 lead to the conclusion that the canals are directly concerned in 

 equilibration. Mach's theory that compensating movements are 

 set up by variations in the pressure of the endolymph seems to 

 be disproved by the experiments of Cyon ('88, pp. 294-297), 

 Spamer ('80) and Ewald ('90, Experiment 42), who secured 

 normal reactions after producing permanent changes in the pre?.- 

 sure of the endolymph by removing the liquid entirely, by 

 replacing it with gelatine or with amalgam, and by inserting into 

 the canals dry bits of laminaria, which swelled up on absorbing 

 moisture, and so mcreased the pressure. 



On the one hand Ayers ('92) draws from his morphological 

 studies the conclusion that the canals are specially modified lateral- 

 canal organs, that have no relation whatever to equilibration. 

 On the other hand SchaefFer ('94) tells us that whirling produces 

 no effect upon tadpoles until after the semicircular canals become 

 developed. But Streeter ('06) has succeeded in separating the 

 action oi the canals from that of the rest of the ear vesicle and 

 concludes that while the ear vesicles are essential to the develop- 

 ment of the power of equilibrium in tadpoles, the canals are not. 



Schafer ('87) succeeded in demonstrating to his own satis- 

 faction that the responses to rotation are due solely to the inertia 

 of the loosely jointed head; he made a wooden model that behaved 

 on the turntable just like a frog or a pigeon, with a few exceptions 

 to be noticed later. 



Other minor experiments have been reported by various inves- 

 tigators, with equally definite but conflicting and inconclusive 

 results. 



5 ANALYSIS AND NEW EXPERIMENTS 



This then appears to be the situation : 



I From the structure of the semicircular canals it was inferred 

 that they were somehow related to the perception of space or direc- 

 tion. 



