114 Proceedings of Royal Society of EdinhiLrgh. [sess. 
indicated methods, and by an exact analysis of every case, that this 
result is arrived at. If any one distinguishes red-blindness from 
green-blindness, it is only because he has not examined into the 
case with sufficient accuracy. 
P. 
Extract from the Report of the Ophtlialmological Society of 
Great Britain on Colour-Blindness, 1880. 
Defective vision of red and green is the form exhibited by every 
one of our 617 pronounced cases. A red or green blind person 
fails in appreciation of both colours. An attempt has been made to 
separate persons found by the wool-test to be colour-blind into the 
“red-blind” and the “green-blind.” But though, according to this 
classification, a large number, perhaps two-thirds of the whole, stand 
clearly under one or the other head, there are many who appear 
equally related to both. 
The distinction between red and green blind is apt to mislead. 
Q. 
Investigations hy Professor Bonders of the Variations in 
Dichromic Vision. 
These investigations are so extensive, and so much scattered 
about in the author’s works, that it is difficult to give a succinct 
account of them in a reasonable space. He gives tables and 
diagrams of experiments made, and he established the existence of 
wide variations, tending to collect in two extreme forms which, for 
convenience, he called “red-blind” and “green-blind,” but without 
attaching to these terms their literal signification. 
The green-blind had, in the part of the spectrum from D to the 
red end, pretty nearly the norihal length of spectrum and strength 
of colour-sensation, differing very little from each other, and these 
formed the larger portion of the whole. 
The red-blind were deficient in the strength of colour, with 
frequently a spectrum shortened at the red end ; they were less 
uniform, and intermediates between the extremes were not wanting. 
The maximum luminosity for the green-blind was near D, but 
for the red-blind was nearer to E. The neutral point for the green- 
