xvii THE SENSE ORGANS 337 



The ear is not only concerned in the perception of sound, 

 but it has a very important function in the relation to the 

 maintenance of equilibrium. Removal of the labyrinth on 

 both sides of the body is followed by loss of ability to main- 

 tain an upright position. Frogs upon which this operation 

 is performed no longer balance themselves on a tilted board 

 so readily as a normal frog will, and when thrown upon the 

 back, they lie there for a long time, and finally right them- 

 selves, if at all, only with the greatest difficulty (Goltz). 

 They are able to swim through the water in a tolerably 

 straight course, but very frequently with the ventral side up, 

 which a normal frog does not do (Breuer). When stimu- 

 lated, they jump about irregularly and move the fore and 

 hind legs in a disconnected and uncoordinated manner 

 (Girard, Ewald). According to Girard and Schrader there 

 is a complete loss of compensatory motions, but this is dis- 

 puted by Steiner. If the labyrinth is destroyed only on one 

 side, the frog takes an asymmetrical attitude. If the opera- 

 tion is performed on the left side, the head is slightly inclined 

 to the left, the right fore limb is held straighter than the left 

 (Girard), the body is bent toward the operated side, and 

 the right hind foot is more extended than the left and sel- 

 dom drawn up to the body (Ewald). The same attitudes 

 are assumed, according to Ewald, for a year after the 

 operation. 



After injury to one of the horizontal canals, the frog tends 

 to move in a circle ; injury to the vertical canals causes 

 abnormal movements in a vertical direction (Hensen). 



If the otoliths are removed from both of the auditory organs, 

 the behavior of the frog, according to Ach, differs from that 

 of a normal individual in several particulars. If the brow 

 of the injured animal is rubbed with the finger, the creature 

 will close its eyes, bow down its head, elevate its back, and 



