56 



HARRY MILES JOHNSON 



Dogs 7 and 8 were rendered temporarily blind by the same 

 method as that used on Dogs i and 2. Dr. Henry Dick, of the 

 department of pathology of the University of Chicago, kindly 

 performed the operation when the puppies were seven days old. 

 Dog 7 was unusually large, but not clumsy. Despite his blind- 

 ness he was able by reason of his fierceness and strength to 

 maintain leadership of the eight dogs with which he was allowed 

 to run. Dog 8 was small and decidedly of the terrier type. 

 He was rather timid among the other dogs, and even in the 

 laboratory his mo\-ements were deliberate. It should be said, 

 howeAcr, that all the animals took readily to training of this 



Figure .5— Floor plan of experimental-room. C, cages F, problem-box contain- 

 ing food; GD, glass exit door; WD, wooden entrance door; dotted line, habit- 

 ual j)ath of animal. Experimenter's station, outside room, by GD. 



kind. They were fed once a day — during the daily test. Imme- 

 diately after the series was completed for the day, each animal 

 was allowed as much food as it would take. All the animals 

 were in excellent, thrifty condition throughout the experimen- 

 tation. 



Dogs I and 2 were between four and five years old when they 

 were introduced to this problem. Dog 5, a stray, was about one 

 year of age. Dogs 6, 7 and 8 were five and one -half months old 

 when work with them was begun. The experiments made on 

 Dogs I, 2 and 5 were between November 5, 1910 and March 

 20, 1 91 1. Those made on Dogs 6, 7 and 8 were between Novem- 

 ber 15, igii and July 12, igi2. 



