130 OTOLITH ORGANS AND SEMICIRCULAR CANALS 



produced by loss of the ampullae. It is especially noticeable that 

 there is the same apparent shght slowing of the reactions and the 

 same indication of lowering of muscle tonus in general. In one im- 

 portant respect, however, the result of this operation differs from 

 that of removal of the ampullae; namely, the compensatory move- 

 ment to rotation about the dorsoventral axis is retained. It should 

 be stated that in these observations due care was taken to ehminate 

 retinal and contact reactions. 



Parker^ removed the saccular otoHth by way of an opening in the 

 roof of the mouth. He found that the loss of this otoHth alone pro- 

 duced no noticeable effect on the equihbrium or the righting reactions 

 of the dogfish, nor did there appear to be any loss of tonus. I have 

 removed this otohth many times by the method I have described 

 above. Its loss does not alter or weaken any of the compensatory 

 movements; it does not disturb the equihbrium or the righting reac- 

 tion, nor is the muscle tonus affected to any noticeable degree. 



Removal of Both Ampulla and Otoliths. 



I may say at once that in accordance with the findings stated in 

 the last section the presence or absence of the large otolith of the 

 saccule is without influence on the equihbrium reactions and it may 

 be disregarded. If, however, the utricular otohth has been success- 

 fully removed and the condition described in a previous section has 

 been attained, namely the retention of compensatory movements to 

 rotations in all planes, the righting reaction, and the maintenance 

 of equihbrium, the consequent removal of the six ampullae produces 

 at once a profound alteration. The condition of a dogfish deprived 

 of the utricular otohth and the six ampullae may be stated in the 

 following way. (1) No compensatory movements are made on rota- 

 tion around any axis whatever. This statement may be modified by 

 saying that in some cases a slow and slight tendency to compensation, 

 requiring many seconds or even minutes for its completion, may be 

 seen. No one famihar with the reactions of the animal would ever 

 confuse this with a labyrinthine reflex. (2) The animal shows no 

 tendency to maintain bodily equihbrium; it swims indifferently back 

 or belly upward. A weak specimen may also come to rest on its 



