43 
-eye should be tested separately, the other being obstructed 
by an opaque disc. 
It is to be noted that any such method of testing only 
.aims at discovering the distant vision of the unaided eye, 
perhaps the most important question in the case of savage 
people. For real accuracy, however, it would be necessary 
to find how far visual acuity could iDe improved by appro¬ 
priate glasses, and if it still proved to be below the average, 
to discover the cause of the defect. But such an examina¬ 
tion requires much special knowledge in the investigator. 
Any obvious cause of imperfect sight, however, such as 
opacity of the cornea, should be noted, and it would be well 
to have a few selected convex and concave glasses so as to 
try whether their use improved defective distant vision. 
(2) Colour vision is most readily tested by the use of 
Holmgren’s coloured wools A They should be thoroughly 
mixed before the examination. A green is shown, and he 
is told to place along with it all the other pieces of wool 
that are of the same colour (irrespective of shade). If he 
does so readily and accurately, he may be passed as of 
normal colour-vision. If, however, he understands what is 
required, yet places wools of any shade of red along with 
the green, or hesitates as to accepting or rejecting a match 
of the green with a wool of some other colour (e.g., grey) 
his colour vision is abnormal.t It is essential that the 
examiner should know the condition of his own colour-vision. 
The person should also be examined as to his power of 
naming colours. In the case of savages this is particularly 
important; it may be found that their language is deficient 
in not having a word to express some colour, e.g., blue. 
R. M. G. 
Further Notes on Testing Sight. 
Perhaps the simplest and the surest measure of keenness 
* These wools, and different forms of Snellen’s Test Types, may be obtained 
from Hawes, 49A, Great Marylebone Street, W. 
t Rules for the use of the wools can be obtained, if greater accuracy is desired. 
