308 MARRIAGE AND DISEASE. 



stages of most cases of progressive degeneration of 

 the optic nerve. Unlike the hereditary affection, the 

 colour-blindness of decay of the optic nerve generally 

 goes on to total blindness. 



As in the case of the haemorrhagic diathesis, this 

 blindness to colours, although rarely found in women, 

 is regularly transmitted through female members of 

 colour-blind families to their offspring, their daughters, 

 like themselves, generally escaping the blight. The 

 following family history offers a good example of the 

 usual course followed in the transmission of this 

 abnormal condition of the visuary apparatus. It is re- 

 lated by Dr. Horner, who was able to follow the colour- 

 blindness through no less than seven generations. 



Those colour-blind are represented by capital letters, 

 those not so affected by small letters : 



M. 



I 



*. 



It is to be noticed, that the second, fourth, and sixth 

 generations of this family were entirely female, and in 

 these the abnormal character did not appear. In the 

 seventh generation, made up of nine males and nine 



