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



cut, there resulted rolling of the eyeball and a convulsive motion 

 of the eyelids. 



When the third pigeon was operated upon, it did not roll 

 sideways as in the case of the first, or tumble backwards as did 

 the second, but tumbled forwards. 



This bird was also preserved for a year. 



A fourth pigeon had all the canals cut in both ears. There 

 resulted immediately an impetuous (fougueux) and confused 

 motion of the head in every direction — from above downwards, 

 from below upwards, from right to left, and from left to right. 



" Ce mouvement etait d'une violence inouie." It so dis- 

 turbed the equilibrium of the animal that it could only obtain 

 some moments of repose by resting its head on the ground. 



M. Flourens tried the effect of removing the osseous covering 

 of the canals, leaving, I presume, in each case the lining mem- 

 brane untouched, so as to prevent the lymph contained in the 

 labyrinth from making its escape. None of the effects before 

 described occurred in this case ; but they exhibited themselves, 

 though in a less degree, when the membranous labyrinth of the 

 respective canals was pricked, the phenomena in each case being 

 the same in character as when the corresponding part of the ap- 

 paratus was cut through — thus showing that the phenomena 

 above described were owing entirely to the action upon the [so- 

 called] acoustic nerve expanded upon the membranous canals. 



The same experiments were repeated upon other pigeons, upon 

 pullets, sparrows, finches, yellow-hammers, linnets, tom-tits, &c. 

 The results, though varying in intensity, were always identical 

 in character. 



After adverting to the circumstance of the experiments having 

 been repeated in the presence of M. Dumeril and himself, M. 

 Cuvier gives his testimony concerning them in the following 

 terms : — 



" La section de chaque canal a produit effectivement les mouve- 

 mens bizarres qui sont annonces dans le memoire. Quelque sur- 

 prenans, quelque inexplicables que sont ces faits, nous ne pou- 

 vons les revoquer en doute." 



The semicircular canals in mammals are enclosed in the pe- 

 trous bone, the hardest and the most compact which their struc- 

 ture exhibits. In order that experiments similar to those prac- 

 tised upon birds might be extended to mammals, it was neces- 

 sary in part to remove this bone; and on this account M. Flou- 

 rens selected as the subject of his experiments young rabbits, 

 animals which possess from birth the faculty of locomotion, at 

 the same time that the bony envelope of their canals does not 

 attain at that early stage of their career its full hardness. 



For operating on the horizontal and posterior vertical canals, 



