CHAP. x. CAUSES AND CURE OF NIGHT-BLINDNESS. 1G3 



this disease is so well known now, that when driving the 

 timber in the spring, the night-blind men always leave 

 the drive in time to reach the shanty by daylight if 

 necessary.' 



' What is the cause of night-blindness ? Did you ever 

 have any satisfactory explanation ? ' 



4 Never ; the lumbermen think it arises from eating 

 too much fat pork during the long winter months. The 

 men do not seem to suffer much pain. There is no 

 inflammation, as in snow-blindness ; the only pain is 

 above the eyes and across the forehead in the line of 

 the eyebrows. It does not interfere with their work in 

 the day-time ; at night they have to be led to their bed, 

 and their food placed before them. They must be treated 

 in every respect like stone-blind men ; but as soon as 

 the sun is about to come above the horizon, they see 

 without difficulty.' 



' You do not think that the snow has anything to do 

 with it, then ? ' 



' Certainly not ; I have been snow-blind myself, and 

 you know well enough what that affection is ; but night- 

 blind men don't suffer at all, as far as I could see. It is 

 worth knowing, perhaps, that night-blind men always 

 recover their sight as soon as they reach the settlements 

 and get a change of diet.' 



M 2 



