Characters, Hereditary and Acquired. 115 



the body as that on which the sciatic nerve had been 

 divided. Effectual irritation may be either mechan- 

 ical (such as gentle pinching), electrical, or, though 

 less certainly, thermal. The area of skin in question, 

 soon after the epileptiform habit supervenes, and 

 during all the time that it lasts, swarms with lice 

 of the kind which infest guinea-pigs — i. e. the lice 

 congregate in this area, on account, I think, of the 

 animal being there insensitive, and therefore not 

 disturbing its parasites in that particular spot ; other- 

 wise it would presumably throw itself into fits 

 by scratching that spot. On removing the skin from 

 the area in question, no kind or degree of irritation 

 supplied to the subjacent tissue has any effect in pro- 

 ducing a fit. A fit never lasts for more than a very 

 few minutes, during which the animal is unconscious 

 and convulsed, though not with any great violence. The 

 epileptiform habit is but rarely transmitted to progeny. 

 Most of these observations are in accordance with 

 those previously made by Brown-Sequard, and also 

 by others who have repeated his experiments under 

 this heading. I can have no doubt that the injury 

 of the sciatic nerve or spinal cord produces a change 

 in some of the cerebral centres, and that it is 

 this change — whatever it is and in whatever part 

 of the brain it takes place — which causes the re- 

 markable phenomena in question. 



3rd. A change in the shape of the ear in animals bom of 

 parents in which such a change was the effect of a division 

 of the cervical sympathetic nerve. 



4th. Partial closure of the eyelids in animals born of parents 

 in which that state of the eyelids had been caused either by 

 section of the cervical sympathetic nerve, or the removal of the 

 superior cervical ganglion; 



I a 



