CANADA PORCUPINE 37 



much shall be allowed for variation in judgment of the experi- 

 menter in these cases? 



3. The resistance of the different parts of the apparatus must 

 be considered with respect to the size, weight, etc., of the ani- 

 mal so that each will have the same advantage in the way of 

 "hair trigger" devices. 



4. The amount of previous experience of the animal with 

 other apparatus must be known and controlled. 



5. The number of experiments in the particular test series 

 which is to be used for comparison must be limited to some 

 definite standard of excellence or to some specific number of 

 reactions. 



6. Similar precautions might be enumerated in respect to the 

 particular devices applied and the order in which they come, 

 the degree of hunger, the presence of the experimenter, the use 

 of negative stimuli, the number of tests per day, etc., etc. Or, 

 at least, all of these conditions should be kept constant through- 

 out any one series of experiments. 



In regard to the work with porcupine No. 11 the following 

 regulations have been strictly observed: 



1. The watch was started when the animal made the first 

 pass at any part of the box. 



2. The watch was stopped when the door came open regard- 

 less of when the animal took notice of it. 



3. No "hair trigger" locks were used. Each device was made 

 to work easily but with a constant friction through a definite 

 distance. 



4. No. II had been captured recently by the author and had 

 had no previous experience in captivity, except a few days 

 general taming and accommodation to cage environment. 



5. All experiences with apparatus are accounted for in the 

 tables and curves, as completely as time will represent them. 



6. The usual hunger of the day was depended upon and after 

 experiments had been completed the animal was allowed to 

 finish eating the daily allowance of food. 



7. No negative stimulus of any kind was employed. 



8. By good fortune the animal in every case succeeded in 

 mastering the new device in a single day, if not by 20 then by 

 40 efforts as the table indicates. 



