374 THE SPECIAL SENSES. 



are more pronounced in some animals than in others, varying 

 apparently with the delicacy of the co-ordination necessary to the 

 movements (Ewald). Thus, the movements of walking or flying 

 in the pigeon may be assumed to require a nicer adjustment of the 

 muscles used than is necessary in the swimming movements of the 

 fish, and in correspondence with this idea it is found that opera- 

 tions on the canals of fishes are not followed by conspicuous effects 

 upon the movements of the animals. 



Temporary and Permanent Effects of the Operation. The 

 general effects of operations on the semicircular canals, so far as 

 disturbances of equilibrium and occurrence of forced movements 

 are concerned, resemble those resulting from operations upon the 

 cerebellum, and, as in the case of the last mentioned organ, it is 

 found by most observers that if the animal is properly cared 

 for the severity of the first effects passes off to a greater or less 

 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 Some unpublished experiments 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 ihco-ordination of the movements of 

 locomotion may be seen. The partial recovery from the operations 

 upon the canals may be due, however, to a more or less complete 

 restoration of the canals to their former functional activity, owing 

 to a regeneration, partial or complete, since a new section of the 

 canals, after a year or more, again brings on the violent and dis- 

 orderly movements of the head and the body. 



Effect of Direct Stimulation of the Canals. The mem- 

 branous canals or their ampullary enlargements have been stimu- 

 lated 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 

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



