250 Mr. R. Moon on the Functions of the Membranous 



hind forwards, while the inferior canal takes the opposite di- 

 rection. 



All the canals are enveloped in a thin bony coating (tunique 

 osseuse mince). 



When the horizontal canal on the left side of a pigeon was 

 cut, a slight movement of the head from right to left and from 

 left to right exhibited itself. This motion continued only for a 

 short time, after which the animal recovered its usual demeanour 

 (allure). Its senses, its intelligence, and the equilibrium of its 

 movements remained perfect. 



When the horizontal canal of the right side of the same bird 

 was cut, the horizontal motion of the head suddenly reappeared, 

 but with a rapidity and impetuosity such that the animal, entirely 

 losing its equilibrium, fell, and for a long time rolled upon itself 

 without being able to stand erect. 



The violent motion of the head ceased after a time, and so 

 long as the animal continued in repose its head continued in re- 

 pose also ; but the moment the animal moved, the motion of the 

 head recommenced, and that motion always became stronger 

 in proportion to the rapidity with which the animal attempted 

 to move itself. 



Thus, when standing still, the animal preserved its equilibrium; 

 it lost it when it tried to walk ; it lost it still more when it tried 

 to walk quickly; it lost it entirely when it tried to fly. The 

 animal feared to move : it saw well ; it could still hear ; it pre- 

 served all its instincts and all its intelligence ; it ate and drank 

 spontaneously, though with great pain. 



M. Flourens observed this bird for a whole year. The wound 

 in the head healed completely ; the bird became very fat ; but 

 the motion of the head, the rolling upon itself, and the loss of 

 equilibrium upon any sudden movement, however slight, always 

 exhibited themselves. 



When the inferior vertical canal on the left side of another 

 pigeon was cut, there immediately ensued a slight but rapid 

 movement of the head from below upwards and vice versa; but 

 this only continued an instant. The animal, when left to itself, 

 could hold itself erect : it walked and flew regularly, except that 

 it experienced from time to time a sharp and sudden motion of 

 the head backwards, which for the moment disturbed its equili- 

 brium and went sometimes almost to the point of throwing it 

 over on its back ; at the end of some moments, however, this 

 movement dissipated itself, or only reappeared after longer in- 

 tervals. 



When the inferior vertical canal on the right side of the 

 same bird was cut, the vertical movement of the head reappeared 

 with a violence and impetuosity in all respects similar to those 



