CEREBRAL CORTEX AND VESTIBULAR NYSTAGMUS 



A true vestibular nystagmus is present in all species of turtles 

 and terrapins received at our laboratory (Chrysemys elegans, 

 Chrysemys concinia, Chelydra serpentina et al.). From two to 

 six quick movements of the eye occur while rotating the turtle 

 through ninety degrees at a rate of one turn in two seconds. 

 From three to twelve postrotatory quick movements occur when 

 rotated ten times at a rate of one turn in two seconds. There is a 

 latent period of from one to four seconds before postrotatory 

 nystagmus appears. Prince ('17) reports such a latent period 

 in very young animals, which I have confirmed. (This, I have 

 found, is also the case in new-born babies.) 



TABLE 1 



Showing the effect of temperature upon the quick component of nystagmus in the 



turtle 



Deviation occurs at 2°C. Temperature was not reduced lower. Deviation 

 disappears at 39° to 40°C. Head nystagmus appears simultaneous with or 

 shortly after the eye nystagmus. Both head and eye movements occur synchron- 

 ously and simultaneously. 



Hemi-decerebration and total decerebration without injury to 

 the optic lobes, midbrain, and underlying nerves have no effect 

 upon nystagmus in the turtle. If the turtle is depressed as a 

 result of the operation, the number of nystagmic movements is 

 diminished or entirely absent. A decided increase in the number 

 of nystagmic movements has been seen not infrequently. (This 

 increase and the effect of lesions of the optic lobe, reported at 

 the meetings of the American Physiological Society, spring, 1919, 

 will be discussed in a later paper.) 



Pigeon. Ewald ('10) reported the presence of true vestibular 

 nystagmus in pigeons. According to Wilson and Pike ('15), it 



