M. Flourens' Experiments on the Ears of Birds, 353 



3. Experiments on the effects produced by dividing the semicircular canals 



in the Ears of Birds. By M. Flourens. 

 At the meeting of the Academy of Sciences of Paris on the 15th Sep- 

 tember last, an interesting report was presented by MM. Portal, Guvier, 

 p-nd Dumeril, on the experiments of M. Flourens, relative to the effects 

 produced by dividing the semicircular canals of the ear in birds. This 

 physiologist had already ascertained that the membrane of the tympanum 

 might be removed without affecting hearing ; that taking the stapes out 

 of the groove which forms the fenestra ovalis weakens sensation ; and that 

 the destruction of the pulp of the interior of the vestibule annihilates it. 

 These results might to a certain extent have been anticipated ; but expe- 

 riments on the semicircular canals produced effects altogether unexpected. 

 Their section did not appear to weaken the sensibility to sounds, but only 

 to render it painful ; while the movements of the animal occasioned by the 

 separation of the parts struck M. Flourens with surprise. He had for- 

 merly, in November 1824, announced this fact with regard to the horizon- 

 tal canals, and subsequent experiments on the others have led to new re- 

 sults. The semicircular canals in the ear of birds, being protected merely 

 by a thin osseous plate, are surrounded by a slight covering of cellular sub- 

 stance, or by openings which communicate with the cavity of the tympa- 

 num. One of the three adheres to the internal wall of the cranium ; the 

 two others approach more to the external wall, and, crossing one another, 

 one goes in a horizontal plane from right to left, the other in a vertical di- 

 rection forwards and backwards. The experiments of M. Flourens were 

 upon these three canals. The section of the horizontal canal constantly 

 produces a motion of the head from right to left, and vice versa; and when 

 the two horizontal canals are divided, this motion becomes so rapid and 

 impetuous, that the animal loses its balance, and rolls over and over with- 

 out the power of raising itself. If the semicircular vertical external canals 

 be cut, a violent motion upwards and downwards takes place ; the animal 

 does not turn round, or roll ov€:;r and over, but falls, often in spite of exer- 

 tions to the contrary, on its back ; and lastly, the section of the semicircu- 

 lar vertical internal canals^roduces violent motions upwards and down- 

 wards, but the animal in this case always falls forward on its bill and tum- 

 bles round in that direction. These motions cease when the bird re- 

 mains at rest ; but as soon as it attempts to change its place they are re- 

 newed, and flight or walking is rendered totally impracticable. - The sec- 

 tion of all these canals induces violent and surprising motions of the head 

 in every direction. These phenomena do not take place on simple destruc- 

 tion of the osseous envelope of the canals, unless the membranous canal 

 and the pulp with which it is filled be also divided. 



An extraordinary circumstance attending these experiments is, that the 

 involuntary motions do not prevent the healing up of the wound, the ani- 

 mal from feeding as usual, and even getting fat. Still however the mo- 

 tions are continued, and M. Flourens has seen pigeons upon which he had 

 operated, and afterwards fed with care, for many months, and even up- 

 wards of a year, fall into the peculiar motions and tumblings corresponding 

 to the divided canal, whenever they attempted to change their position. 

 VOL. X. NO. II. APRIL 1829- Z 



