552 



PHYSIOLOGY 



CHAP. 



ganglion cells of the cortex. Sergi (1902) observed phenomena 

 analogous to the above on applying curare to the cortex of the 

 guinea-pig; Baglioni and Magnini noted an increase of faradic 

 excitability, expressed by a drop in the threshold of excitability. 



That the action of these specific poisons (strychnine, picro- 

 toxin, curare) is exerted electively on the cortical ganglion cells, 

 and does not spread to the nerve-fibres of the corona radiata, 

 is demonstrated by the fact that both the increase in faradic 

 excitability and the rhythmical contractions disappear .immediately 



FIG. 279. Plan of left hemisphere in Macacus brain. External surface. (Horsley and Schafer.) 



and for ever so soon as the poisoned area of the cortex is excised 

 or damaged by other poisons. 



The fact that carbolic acid, which picks out the motor cells of 

 the ventral horn of the spinal cord, has no action nor depressing 

 effect on the cortex led Baglioni and Magnini to conclude that 

 the ganglion cells of the cortical motor zone are not of the same 

 nature as, and cannot be identified with, the motor cells of the 

 cord through which they indirectly exert their motor effect, and 

 should rather be compared with the cells of the dorsal horn of the 

 spinal cord in their property of reacting to strychnine. 



Later work on the dog's brain added to the number of excit- 

 able centres. H. Krause (1884), on applying electrical stimuli to 

 an area lying somewhat external to and in front of Ferrier's point 



