HABIT FORMATION IN THE DOG 73 



another blind litter brother not used in these experiments 

 actually outgrew all the other members of the litter of seven. 

 Dog 8, which was smaller at birth thrived well, while another 

 blind male of the same litter, which was rather weakly from 

 the beginning, died at four months of indigestion. There is 

 no reason why a puppy which has undergone this operation 

 should not live as thriftily and happily as a normal puppy if 

 given proper care. But in clipping away enough of the edges 

 of the eyelids to insure the formation of strong scar tissue some 

 small glands are necessarily destroyed. While the dog is kept 

 blinded, too, the small drain which is left at the corner of the 

 eye is likely to become clogged and a slight infection may 

 develop sufficiently to injure the cornea. The apparatus of 

 accommodation may atrophy for want of use. A histological 

 examination of the optic tracts of Dogs i and 2 will be made 

 at some time in the future, in order to determine whether there 

 was deterioration there. 



Dogs 7 and 8 were operated on, 30 May, 191 2, by Dr. Conrad 

 Jacobson of the Johns Hopkins Hospital. Recovery was un- 

 eventful'. The right cornea of Dog 8 was found considerably 

 clouded, but cleared up to some degree in about two weeks 

 after the operation. Dog 7 was apparently in good condition, 

 although it was difficult to detect any change n his behavior. 

 Substantially the same test was performed on him and Dog 

 8 as was made on Dog i . There were no other persons present, 

 so the obstruction, a board two feet wide and seven feet long, 

 covered with white cheesecloth was placed directly in his habitual 

 path from one room to another. Its position was changed after 

 each trial. The door was opened by a weight -and-pulley sys- 

 tem, and the operator released it just before calling the dog. 

 Dog 8 collided once with the board, avoided it the next two 

 consecutive times, collided the third and afterwards came into 

 the room crouching and keeping to the wall. Dog 7 never 

 bumped into the board. These tests were made fourteen days 

 after the operation. Dog 8 avoided the board successfully in 

 each of ten trials on the twenty-first day after the operation. 

 In their other behavior absolutely no other change could be 

 noted. Both of them in the blind state had found their way 

 about the laboratory and yard. From about a month before 

 the operation the animals were kept in a building at Home- 



