720 THE CEREBRAL CORTEX. 



Landois l found that convulsive movements can also be produced, in a 

 regular march, by the application of chemical irritants to the surface of the 

 brain. 



The character of the muscular contractions in artificially provoked 

 epilepsy has been studied in dogs by Francois-Fran ck and Pitres ; 2 and in 

 monkeys, rabbits, and dogs by Horsley and myself and others. 3 Franqois- 

 Franck and Pitres generally obtained in the animals they employed (which 

 were usually allowed to partially recover from the influence of the anaes- 

 thetic for the purpose of the observation) an after-effect of a tetanic nature 

 lasting for a few seconds; this was practically a continuation of the contrac- 

 tion which was evoked by the faradic current, but often of a more pro- 

 nounced character. This " tetanic phase " was succeeded, usually quite 

 suddenly but sometimes gradually (Figs. 327, 328), by the " clonic phase," 

 characterised by the violent spasms of slow rhythm which have already 

 been noticed, and which would last a variable time (from a few seconds 

 to several minutes), slowly passing off but sometimes succeeded by a 

 second or a third fit or even more. They note that the tetanic phase 

 was occasionally absent, and this was the case also in many of the 



FIG. 328. M, Curve of the contraction of a muscle during and after cortical excita- 

 tion, showing the tetanic and epileptoid after-effect. Pr.c., carotid pressure. 

 E marks the period of excitation. Fran9ois-Franck and Pitres. 



experiments recorded by Horsley and myself, in which the animals were 

 the whole time completely under the influence of the anaesthetic employed 

 (chloroform or ether). As the attack subsides, the clonic spasms become 

 slower and more irregular, and are often attended by short intervals 

 of quiescence. In some cases the muscles affected pass towards the 

 termination of the fit into a condition of contracture. Similar pheno- 

 mena have been noted in attacks of cortical (Jacksonian) epilepsy in 

 man. If the cerebral cortex be in a condition of abnormally increased 

 excitability, the excitation of a sensory nerve may serve to provoke an 

 attack of epilepsy. 4 Likewise, if excitation of a sensory part of the 

 brain (at least of some part other than the Kolandic region) fail to 

 provoke epilepsy, an increase of excitability of the motor area, such as 

 is brought about by exposure and previous stimulation, will render the 

 excitation of the sensory area effective. These facts have some bearing 

 upon the causation of idiopathic epilepsy in man, the fits in which, as is 

 well known, are usually preceded by a sensation known as an aura, 



1 Wien. med. Presae, 1887, Nos. 7 to 9. - Loc. cit. 



3 Journ. Physiol., Cambridge and London, vol. vii. 



4 Francois-Franck, " Lecons," p. 119. 



