CEREBRAL CORTEX AND VESTIBULAR NYSTAGMUS / 



Observations upon the time of occurrence of nystagmus in 

 new-born kitens confirm those of Prince ('17). Well-defined ves- 

 tibular nystagmus does not appear until the end of the second 

 week and the after-nystagmus is preceded by a latent period in 

 kittens and pups. (Observations which will be published later, 

 have been made upon new-born babies.) 



Dogs. Rotatory vestibular nystagmus is present in the dog to 

 the same degree as it is in the rabbit. Postrotatory nystagmus, 

 however, is not so marked in the dog as in the rabbit. The av- 

 erage number of postrotatory movements for thirty dogs when 

 rotated ten times at a rate of one turn in two seconds was six, 

 the average time of duration being four seconds. One dog in 

 this series had to be rotated at a rate of one time per second in 

 order to elicit a postrotatory response of four movements. In 

 other words, individual variation occurs in dogs as in rabbits 

 and other animals studied, which necessitates the determination 

 of the normal of the dog before operating. 



Ablation of the eye-motor area of the cerebral cortex, also with 

 inclusion of the lateral and basal portions of the temporal lobe, 

 does not abolish the quick component of nystagmus. On the 

 contrary, there is an increase in the rotatory nystagmus when 

 rotated to the side of the lesion and a marked increase in the post- 

 rotatory nystagmus when rotated opposite to the side of the lesion. 

 This increase is more or less temporary, but persists as long as 

 six and eight months (dog V, table 3) in two animals permitted 

 to live that long. This increase consists in a five- to fifteen-fold 

 increase in the number of movements and a two- to four-fold 

 increase in the time of duration of the after-nystagmus. This 

 marked increase only lasts from one to three weeks, after which 

 it reduces gradually to only a two- or three-fold increase. The 

 magnitude of the quick component is decreased, that is the arc 

 through which the eye is moved during the quick component is 

 decreased as compared with the normal. 



There is also a tendency for the quick movements to occur with 

 the eye deviated, i.e., the quick movement does not bring the 

 eye back to the primary position, as normally occurs, but only 

 partially (from one- to two-thirds of the normal arc) . This tend- 



