456 Beuj. C. Gruenherg 



It may accordingly be safe to conclude that while the turnings 

 of the head on rotation may be responses to visual impressions, 

 they may also be quite independent of visual impressions. One 

 is therefore driven back to a reexamination of the semicircular 

 canal theory, or to search for some other means of perceiving 

 movement or acceleration. 



It had already been found that there is not complete loss of 

 the compensatory movements on cutting the acoustic nerves,'^ or 

 on destroying the semicircular canals. This is comprehensible, 

 since the eyes are also capable of leading to similar results. If a 

 frog that has been operated upon is rotated with the eyes covered, 

 or surrounded by some opake medium that rotates with him, there 

 is no response. This excluding of visual impressions is not, as 

 Cyon supposed, eliminating the determining factor, since the nor- 

 mal frog under the same conditions will continue to react, though 

 Cyon failed to observe this. The results referred to in this para- 

 graph I have verified experimentally. 



The following is the record of one frog whose semicircular canals 

 had been destroyed by piercing into the capsule from the dorsal 

 side. The animal was etherized; there was no bleeding. 



1 Immediately after the operation (the animal recovered con- 

 sciousness and began to move about sluggishly within two or 

 three minutes after the operation): 



a Animal lies on back quietly over one-half minute at a time 

 without making efforts to right itself. 



b Rights itself only with great difficulty and after making 

 many awkward movements. 



c Limbs not correlated in crawling about; does not hop. 



(1 On turntable, no response. 



e In swimming, rolls from side to side. 



2 After thirty mmutes: 



a Lies on back for short intervals, but not quietly. 

 b Rights itself with difficulty, but more quickly than at first. 

 c Moves about awkwardly, but better than at first; can hop, 

 but in jumping frequently lands on back. 



^Vide supra. 



