i 7 2 COMPARATIVE PHYSIOLOGY OF THE BRAIN 



great force ; if the crura cerebelli ad medullam ob- 

 longatam be severed the animal goes backwards or 

 shows a tendency to turn somersaults backwards. 

 " La direction des mouvements produits par la section 

 des fibres de 1'encephale est done toujours determinee 

 par la direction de ces fibres" (Flourens). 



Flourens called attention to the analogy of these 

 phenomena with those he observed after lesion of the 

 semicircular canals. This analogy, however, does not 

 exist just as he states it. He compares the effect of 

 the one-sided division of the pons with the division 

 of a horizontal canal. This is not correct. So far 

 as I know, such a lesion does not produce rolling mo- 

 tions about the longitudinal axis in any animal. On 

 the other hand, destruction of a whole ear, probably 

 in most cases, causes rolling motions. Flourens 

 states further that after destruction of the anterior 

 canals an animal turns somersaults forwards, after de- 

 struction of the posterior canals backwards. Flourens 

 assumes that the nerves of the three canals continue 

 into the corresponding peduncles of the cerebellum, 

 and that this origin of the nerves is the cause of the 



o 



phenomena that we observe after lesion of the single 

 semicircular canals (3). But this is probably not cor- 

 rect, since the auditory nerve ends in the medulla. It 

 is possible, however, that the cerebellum is connected 

 with the same motor elements in the medulla with 

 which the acoustic nerve is connected. The cerebel- 

 lum might thus appear as an appendage of the acous- 

 tic segments. 



