1912.] 



Instability of Cortical Points. 



275 



Although the epileptiform clonus has often been confined to one of the 

 antagonistic muscles, either flexor alone or extensor alone, sometimes it has 

 appeared in both these muscles together (figs. 12, 17, 18, 19, 20); the effect 

 has then been sometimes exquisitely reciprocal (fig. 20), but not uniformly so, 

 a sudden break in the rhythm of the clonus of one muscle occasionally 

 disturbing the mutual relation. 



Subsequent to a partial epileptoid after-discharge we have frequently found 

 the area of cortex whence the discharge was initiated irresponsive for a time 

 (post-epileptic exhaustion of Francois- Franck and Pitries). In our experi- 

 ments this was particularly noticeable in the case of the cortex of the 

 anthropoid ape, the chimpanzee (fig. 12), and more marked than in the case of 

 the smaller monkeys (macacus) which we have used. 



(c) Rebounds. 



In his interesting monograph on the reactions of the motor cortex of the 

 dog, A. de Uchtomsky* has called attention to rebound effects, both 

 excitatory and inhibitory, following cortical stimulations, and furnishes 

 excellent illustrations of them. From his work we gather in comparing with 

 it our observations on the monkey that cortical rebounds tend to occur more 

 frequently in the dog than in the monkey. 



We have seen on several occasions that a cortical stimulus which produces 

 inhibition of one of the muscles under observation is, on its cessation, followed 

 by a contraction of the inhibited muscle. This contraction appears to be a 

 rebound contraction similar to the rebound contractions which are exhibited 

 so frequently by extensor muscles after an inhibitory reaction in the 

 decerebrate preparation, and more rarely in purely spinal preparations. In 

 the experiments with the cortex we have met with examples of rebound 

 contractions both in the extensor and in the flexor muscles (figs. 21, 22). 

 They are not, however, in our experience nearly so often met with as in the 

 reflex reactions of the decerebrate preparation. 



* ' On the Dependence of Cortical Motor Reactions upon Central Associated Influences 

 (Russian), Moscow, 1911. 



