On Light in some of its Relations to Disease, 155 



that there exists in a very large proportion of them a pre- 

 disposition either hereditary or acquired by the individual 

 subject to them. 



This predisposition to functional nervous affections is 

 well established by the observations of careful and candid 

 investigators, and is verified by the daily experience of 

 many physicians. Persons possessing this unfortunate 

 predisposition are liable from slight immediate causes to 

 such troubles as neuralgia, headache, epilepsy, hysteria, 

 insanity, and even consumption. In a large proportion of 

 instances this predisposition is hereditary; and this in- 

 herited relationship to disease, while it has been carefully 

 investigated by a few of our most able observers, has by 

 the greatest number of practitioners of medicine been 

 altogether too much overlooked. One who will investigate 

 these hereditary tendencies will be surprised to find in how 

 great a proportion of the victims of nervous trouble there 

 is a family history of kindred affections. Thus a person 

 who is an habitual sufferer from neuralgia may remember, 

 when questioned, that one of his grandparents was also 

 neuralgic, that his mother was a victim of oft-recurring 

 nervous headaches, that his aunt has hysteria, and his 

 cousin possibly epilepsy ; and that, of his brothers and 

 sisters, some have headaches or neuralgia, and others are 

 called nervous people. 



Not long since I saw a boy of sixteen, who for ten years 

 has been subject to epileptic fits. His mother, who was 

 for many years subject to similar fits, died in early woman- 

 hood; her father, who is still living, has during the last 

 few years been epileptic ; and by an interesting coinci- 

 dence, on the day that I first saw the boy I also met a 

 cousin of the mother, a resident of a distant town, who 

 was himself a sufferer from this terrible malady, and whose 

 mind had already become enfeebled by the disease. 



Here is another instance, and one which, with slight 



