6 A. C. IVY 



Complete decerebration in the rabbit does not abolish the 

 quick component of nystagmus. The entire thalamus can also 

 be destroyed (figs. 8 and 9) without abolishing the quick compo- 

 nent. In the decerebrate rabbit the quick component persists 

 until the animal becomes depressed because of degenerations in- 

 volving lower centers or because of inanition, it being very diffi- 

 cult to keep these animals in a good state of nutrition. In the 

 decerebrate rabbit with destruction of the thalamus the tempera- 

 ture becomes subnormal and the quick component disappears, 

 but will return again, if the animal is placed in an incubator and 

 its body temperature raised to normal. Deviation still persists 

 with subnormal temperature. In such a rabbit immediately 

 after the operation and for four to five hours later the quick com- 

 ponent is very manifest, but after this time it is irregular and sub- 

 ject to wide variations. Two such animals manifested no rota- 

 tory quick component when tied to a board, but when held in 

 the hands and rotated the quick component was present. With- 

 out taking into consideration these last two points, along with 

 body temperature, one might overlook the presence of the quick 

 component in rabbits without cerebrum and thalamus. 



The rabbit is a convenient animal in which to demonstrate the 

 presence or absence of the quick component following various 

 brain lesions. 



Cats. Six cats have been worked upon with the same results 

 as observed in the rabbit and the dog. 



Kittens and pups. The same observations hold true in young 

 animals as observed in the adult, except for a general rule that 

 the depression from the operation is less marked and the effects 

 produced are more temporary. However, one pup, which was 

 operated at the age of four months and is now one year old 

 (August 1, 1919), in which the left motor cortex, occipital cortex 

 and basal portion of the temporal lobe was extirpated, now shows 

 three postrotatory movements when rotated to the left, and 

 eight when rotated to the right. The increase in the after- 

 nystagmus when rotated opposite to the side of the lesion seems 

 to be permanent in this pup. 



