344 POPULAR SCIENCE MONTHLY. 



THE BEHAVIOUE OF BLIND ANIMALS. 



By Professor WESLEY MILLS, M.A.. M.D., 



MCGILL UNIVERSITY, MONTREAL. 



IN the course of years I have had the opportunity of observing a con- 

 siderable number of animals totally blind in either one or both eyes 

 and to these only shall I refer in this paper. 



Pigeons. All those observed, that were otherwise normal, have been 

 blind on one side only. The defect does not seem to have resulted in 

 any great inconvenience or disadvantage to the individual. Birds do 

 not, it is likely, possess binocular vision, in the sense in which the term 

 may be applied to many mammals; and in consequence of the defect, 

 cutting off the field of vision on one side completely, the bird endeavors 

 to make up for this by adaptive movements of the head, which it can 

 bring about with a facility not possible to the mammal. 



It also, through experience, becomes more alert than the average 

 pigeon; nevertheless, when the struggle for existence becomes keen, as 

 for example when a limited quantity of food is strewn about, it is 

 shown to be plainly at a disadvantage, both in securing the food and in 

 the bodily conflicts that are apt to arise between it and its competitors. 



White Rats. I have observed several white rats, some of which were 

 blind in only one eye, others in both. The results were in some respects 

 very different from what might have been expected, and in this the 

 difference between the bird and the rabbit, on the one hand, and the rat, 

 on the other, was striking. 



Even in the case of total blindness, the rat is not handicapped as one 

 might suppose must be the case. In a very few days the rat blind in 

 only one eye seems to ordinary observation to be in no appreciable 

 degree worse off than his fellows. In a short time the specimen, totally 

 blind, moves about so well that one would need to look carefully to be 

 assured that he gets no assistance from the visual sense. But in his case 

 there are times when it is evident that he is handicapped. In exploring 

 new surroundings he proceeds with special caution, stretching out his 

 neck, sometimes resting on his hind legs, more frequently elevating his 

 fore parts and sniffing in an unusual way, showing an extreme care and 

 plainly making use of his acquired greater facility, or perhaps one 

 should say, his accustomed and habitual greater use of senses that 

 normally are not required to function to such a marked degree. 



He is also somewhat more timid and retreats in the way rats do 

 toward their place of exit, with greater readiness. He is of course more 



