SEMICIRCULAR CANALS AND THE VESTIBULE. 



405 



Flourens's Experiments upon the Semicircular Canals. 



Modern experiments and theories concerning the functions of the 

 semicircular canal date from the classical researches of Flourens* 

 (1824). This investigator laid bare the canals in birds and mam- 

 mals and studied the effects of sections of one or more of them. 

 The experiments have since been repeated by numerous observers, 



Fig. 180. Dissection to show the position of the three semicircular canals in the pigeon 

 and the relations of their ampullary ends (from preparation made by Dr. Esther Rosen- 

 crantz). 



and the results obtained have been described in great detail, for an 

 account of which reference must be made to original sources.f In 

 general, it may be said that injuries to the canals are followed by 

 certain more or less definite movements of the head, eyes, and body, 

 and by a disturbance in the power of the animal to co-ordinate nor- 

 mally the muscles used in standing, locomotion, or flying. The 

 character and extent of these results vary with the number of 

 canals injured, and, indeed, show a more or less definite relationship 



* Flourens, " Recherches experimentales sur les propriety et les fonctiona 

 du systeme nerveux," second edition, 1842. 



t The literature of the semicircular canals and the vestibule is very ex- 

 tensive. The complete bibliography may be obtained from the following 

 sources : " Die Lehren von den Funktionen der einzelnen Theile des Ohrlaby- 

 rinths," by von Stein, 1894; Richet's " Dictionnaire de Physiologic," article 

 by Cyon, on "Espace," 1900. Ewald, "Physiolog. Untersuchungen u. d 

 Endorgan des nervus octavus," 1892. 



