3i8 Journal of Comparative Neurology and Psychology. 



rant of these objections, and so far as they are legitimate, they 

 will hold against my work. But I do not think the presence of 

 hunger can be considered as vitiating the experiments. The 

 desire for food is a natural condition, and can scarcely be regard- 

 ed as an abnormal stimulus in an)- case. The guinea pig is a 

 phlegmatic animal, insusceptible to considerable variations of 

 temperature and food, as one would naturally suppose from its 

 thick covering of fur, and its ready accumulation of fat upon 

 which it may live. When beginning my experiments even with 

 animals perfectly tame, the problem was to get them to attend 

 to the food in the problem box. The incentive to obtain the 

 food had to be rendered quite strong. My custom was to feed 

 the guinea pigs once a day, about five o'clock in the afternoon ; 

 enough hay and oats were left in the cage to last all night and 

 well into the next morning. Those animals with which I in- 

 tended to experiment were left unfed one day and experiment- 

 ed with at about 2:30 p. m. the next day, when they were fed as 

 usual. This was found to produce the requisite degree of hun- 

 ger to gain attention to the problem, though there was nothing 

 like the "utter hunger" of Thorndike's cats and dogs. In no 

 case was there "frantic activity" indicative of an abnormal state. 

 Previous observations had demonstrated that hunger any less 

 intense did' not succeed in eliminating mere curious exploration, 

 or even quiescence in one corner of the cage. 



Upon first introducing the guinea pigs into the laboratory 

 they were wild and easily frightened, and disturbed by my pres- 

 ence, or by any unusual sound or movement. An attempt was 

 made to carry on the experiments in their customary room, but 

 the sight of the other guinea pigs, and when that was shut off, 

 their sound proved a disturbing factor. For that reason the 

 animals to be experimented upon were removed to another 

 room. 



A few weeks of persistent and continuous petting, hand- 

 ling and training finally accustomed them to the presence of the 

 experimenter, and gradually the problem came to absorb atten- 

 tion to the neglect of any outside element. Animals born in 

 the laboratory did not have to pass through this preliminary 



[26] 



