7 i8 



THE CEREBRAL CORTEX. 



on this subject are examined, it is found that the results are closely 

 dependent upon the establishment of an irritative lesion in parts which 

 are either directly in, or in close proximity to, the path taken by motor 

 impulses, and the resultant rise of temperature may therefore well be 

 due to an increased activity, chemical or otherwise, of voluntary muscles, 

 caused by irritation extending to the motor tract. 1 



Epilepsy from Coktical Excitation. 



As already stated, Fritsch and Hitzig obtained, as the result of 

 strong or prolonged stimulation of the excitable points which they had 

 marked out in the dog's brain, after-actions of the muscles which had 

 been called into activity ; these after-actions took the form of clonic 



Fie. 327. — Curves obtained from a dog's muscle as the result of strong 

 excitation (A) of the cortex cerebri, (B) of the subjacent corona 

 radiata. E, E, period of excitation ; T, contraction during excit- 

 ation ; Ep (in A), epileptoid contractions. In A the cessation of 

 the excitation is followed by gradually developing epileptoid spasms, 

 which appear to be formed by the fusion of smaller contractions. 

 In B the rapid fall of the muscle lever indicates the entire absence (0) 

 of an after-effect. — Francois- Franck and Pitres. 



spasms, or even in some cases passed into well-characterised epileptic 

 tits, spreading eventually to all the muscles of the body. The 

 character of the after-contractions thus obtained is shown in the 

 annexed tracing (Fig. 327, A), where it will be seen that each clonic 

 spasm of a muscle is formed by the summation of a certain number of 

 contractions, which succeed one another at the ordinary rhythm of 

 discharge of the nerve centres. This summation occurs in the nerve 

 cells of the cortex cerebri and not in the lower nerve centres, for, as 

 already mentioned, it was found by Gotch and Horsley, by the aid of 

 the capillary electrometer, 2 that the passage of the nerve impulses 

 down the spinal cord is accompanied by an electrical disturbance 

 having the same rhythm as the muscular clonus. 



1 The formation of heat within the cortex itself has been studied by Mosso (Croonian 

 Lecture, Phil. Trans., London, 1892, B). Cf. Hill and Nabarro, Journ. Physiol., Cam- 

 bridge and London, 1895, vol. xviii. p. 218, and article " Animal Heat," this Text-Book, 

 vol. i. p. 808. 



- Phil. Trans., London, 1891, B, p. 267. 



