CHAP, ii.] THE BRAIN. 731 



die away, whereas these phenomena may last for at least a very 

 considerable time. The movements are not occasioned by any 

 partial paralysis, by any want of power in particular muscles or 

 group of muscles ; though removal of the canals of one side has 

 been described as leading to diminished muscular tone, especially 

 on the same side of the body, the mere diminution of force is 

 insufficient to explain the phenomena. Nor on the other hand 

 are the movements due to any uncontrollable impulse ; a very 

 gentle pressure of the hand suffices to stop the movements of 

 the head, and the hand in doing so experiences no strain. The 

 assistance of a very slight support enables movements otherwise 

 impossible or most difficult, to be easily executed. Thus, though 

 when left alone the bird lias great difficulty in drinking or pick- 

 ing up corn, it will continue to drink or eat with ease if its beak 

 be plunged into water, or into a heap of barley ; the slight sup- 

 port of the water or of the grain seems sufficient to steady its 

 movements. In the same way it can, even without assistance, 

 clean its feathers and scratch its head, its beak and foot being 

 in these operations guided by contact with its own body. 



The amount of disorder thus induced differs in different 

 birds ; and some movements are more affected than others. As 

 a general rule it may be said that the more complex and intri- 

 cate a movement, the fuller and more delicate the coordination 

 needed to carry it out successfully, the more markedly is it dis- 

 ordered by the operation ; thus after injury to the canals, while 

 a pigeon cannot fly, a goose is still able to swim. 



Similar phenomena have been observed in other classes of 

 animals than birds, in mammals, in frogs and in fishes. The 

 results, which are more striking in some species of animals than 

 in others, may be described by the following general statements. 

 When one canal is severed the head or the eyes, and, in certain 

 cases, parts of the body, in a fish for instance the fins, make 

 certain definite movements, or take up certain definite positions, 

 or tend to do so, the exact characters of the movement or of 

 the position taken up depending upon which of the canals is 

 the one operated on. After the operation, a certain deficiency, 

 a certain want of coordination, in the movements of the animal 

 may be observed, the exact nature of the loss differing with the 

 different canals ; but this is generally slight and after a while is 

 overcome by accommodation. Section of all three canals on 

 one side is followed by effects in the way of movements and the 

 like which may be regarded as the sum of the effects of the 

 severance of each canal ; the in coordination is made more pro- 

 nounced, but may in time apparently disappear. When all 

 canals on both sides are severed, the resulting special movements 

 are not so striking or may be absent, but the loss of coordination 

 is still more pronounced and may be permanent. The like 

 results have been obtained, at least by some observers, by 



