SEMICIRCULAL CANALS AND THE VESTIBULE. 407 



extent. Flourens states that his pigeons, with two or more canals 

 cut, continued to show the effects of the operation almost with the 

 same intensity for nearly a year. Some unpublished experiments 

 made in the author's laboratory have given different results.* 

 Pigeons with only one canal cut recover practically completely 

 within ten or more days. Those with two canals cut recover nearly 

 completely within a month, so far as walking is concerned, although 

 they exhibit an unwillingness to fly. Those with three or more 

 canals cut never recover completely, but their final condition is very 

 different from that exhibited shortly after the operation. Even 

 when all six canals have been cut the animal, if well cared for in the 

 beginning, is able finally to stand and walk and feed itself. It 

 is not able, however, to fly, and in walking its progress is uncertain; 

 there is a tendency to walk zigzag or in circles, first to one side, then 

 to the other. If hurried or excited some return of the violent 

 movements of the head and inco-ordination of the movements of 

 locomotion may be seen. If, instead of cutting the canals, the 

 ampullae are destroyed, the initial effects of the operation seem 

 to be less violent, owing possibly to the fact that in the former 

 case the irritative effects of the lesion still have the end organs 

 in the ampullae to act upon. Pigeons with all six ampullae 

 destroyed may make eventually an excellent recovery. Within 

 a few months they walk and perch with little difficulty when 

 not frightened. In the matter of flying they do not recover 

 their former skill, but this may be due to lack of practice, since 

 in the experiments quoted (Rosencrantz) no provision was 

 made for exercise in flying. The very marked degree of recovery 

 noted, even after loss of all six ampullae, seems to be due to the 

 fact that the animal learns to use his other sensory data in 

 co-ordinating his muscles. If after a nearly complete degree of 

 recovery has taken place a new operation is performed in which 

 the canals are cut, the resulting disturbance to motion is relatively 

 small and soon passes off. That there is any effect at all from 

 the second operation may be due to the emptying of the endo- 

 lymph and the consequent effect upon the remaining ampullae, 

 or, if these had all been previously destroyed, to the effect upon 

 the sense organs of the vestibular sacs. 



Direct Stimulation of the Canals. The membranous canals or 

 their ampullary enlargements have been stimulated by many 

 observers and by many different methods electrical, chemical, 

 and mechanical. The results of electrical stimulation are not 

 constant nor striking, but chemical and especially mechanical 

 stimulation in the hands of many observers has called forth definite 

 movements of head or eyes similar in a general way to those caused 

 by section of the canal, but lasting, of course, for a short time only. 



* Experiments lasting over two years made by Dr. E. Rosencrantz. 



