20 HARRY MILES JOHNSON 



3. To find the difference -threshold for pitch in the dog. 



4. If preliminary results should justify the attempt, to repeat 

 the tests on animals on which after training, extirpation opera- 

 tions had been performed by a competent surgeon, and attempt 

 to interpret the disturbances which might result in the light 

 of the post mortem examinations. 



The statement may properly be made now that neither of 

 the two goals last mentioned has as yet been reached. 



The animals used were two females, litter sisters, mongrels, 

 littered June 15, 1906. At about their second day of life a 

 surgeon in the state hospital for the insane at Wards Island, 

 New York, had assured the continuance of temporary blindness 

 as long as might prove desirable, by first scarifying the edges 

 of the lids and then uniting them with stitches. This caused 

 the upper and lower lids to grow fast together before the ninth 

 day, at which time the puppy's eyes ordinarily open. During 

 the preliminary experiment described herein the dogs were still 

 in the blind state. When this work was begun they had been 

 in the laboratory for over a year but no experiments of con- 

 sequence had been made with them. Both were laboratory 

 pets and very affectionate, but rather nervous in strange situa- 

 tions. 



It seemed best, in order to obtain decisive results, to present 

 the animal with at least fifteen stimuli at each daily test. If 

 a small number — say five, is chosen, variation in the order of 

 presentation is too greatly limited ; and if the animal is nervous 

 at first the record is not a fair indication of his discriminatory 

 work. 



The animals used in this experiment were fed once a day — 

 at the time set for the experiment, which was early in the after- 

 noon. No food was given until the day's work was begun. If 

 the animal appeared unduly eager to begin work one or two bits 

 of meat were usually given before the stimulus was presented, 

 in order to make the dog better contented. After each day's 

 series each animal was allowed to eat as much as she desired at 

 the time. The food was scrap meat, thoroughly cooked by boil- 

 ing, and mixed with stale bread soaked in its liquor. Milk was 

 also given from two to seven times a week. Both these and the 

 other animals used in later work remained in splendid condition 

 throughout the experimental work. 



