On Light in some of its Relations to Disease. 157 



gular and what seemed a constant relation between chorea, 

 or St. Vitns's dance, one of the most characteristic and 

 clearly-defined forms of nervous affections, and certain pe- 

 culiarities in the manner in which light entered the eyes of 

 the patients ; and I was struck with the remarkable fact that 

 intractable cases of chorea yielded when the conditions for 

 correcting the eye-troubles w^ere complied with. These 

 circumstances w^ould have led me to suppose that both the 

 chorea and the visual defect were the result of a common 

 cause, and that the remedy for one happened to be the 

 remedy for the other ; but, as the eye-troubles were not 

 diseases, but, simply natural peculiarities, which caused 

 these patients to see at a disadvantage, that these condi- 

 tions were congenital, and in many instances simply 

 family features, as characteristic as the form of the nose 

 or the shape of the head, it became evident that, if any re- 

 lationship existed between the eye-feature and the nervous 

 disturbance, it must be the relation of cause and effect, 

 and that the permanent and inherited feature must be the 

 cause. Further investigation revealed the fact that in 

 other forms of nervous troubles similar relations were 

 formed. As those in whom I had discovered these rela- 

 tions were in almost every instance patients on account of 

 a particular class of affections, I thought it best to search 

 among the patients of those who were engaged in more 

 general practice. Accordingly, the kind offices of many 

 of my medical friends were brought into requisition to 

 furnish the material, from general practice, for this inves- 

 tigation ; but the results were the same as before. Hence 

 I was led to conclude that, as a general rule, certain forms 

 of visual defect and functional nervous diseases were in 

 relation to each other as cause and effect. 



Before proceeding further let us briefly review some 

 points in the physiology of vision. When rays of light 

 fall upon the surface of a healthy eye, they pass through 



