BEHAVIOR OF WHITE RATS IN PRESENCE OF CATS 25 



Cannon 4 and others suggest, however, that physiological inves- 

 tigations might furnish a more definite answer to this question. 



2. Having in mind age and sex differences, the above experi- 

 ments were repeated with many pairs of rats and with five differ- 

 ent cats. Save for the litters of very young rats, the behavior 

 was so uniform as to obviate the necessity of a detailed presenta- 

 tion, the responses varying chiefly in degree. A few of the sub- 

 jects whined but all gave unmistakable signs of disturbance. 

 Only five or six displayed the bodily contractions, three being 

 females. There seems to be no sex difference save when the 

 female is pregnant or is suckling a litter. In these cases, the reac- 

 tion appears a little more marked. The younger rats, especially 

 those two months old, were highly excitable, running nervously 

 from one part of the box to another whenever the cat changed 

 its position. A group three weeks old presented a comical pic- 

 ture. They were hardly strong enough to maintain a rigid posi- 

 tion and their eyes were not yet accustomed to the light, having 

 opened only the day before. Their attitude was just as charac- 

 teristic and specific, however, as that of any of the adults. The 

 performance of the group two weeks old is a little questionable. 

 There was, of course, no bodily posture taken. The judgment 

 had to be made entirely in terms of the amount of activity mani- 

 fested in squirming about the nest seeking the mother. In the 

 presence of the cat, these movements almost ceased, the quiet- 

 ness being unusual after the cat was removed; but the quiescence 

 was in no other way striking. The day-old group made no re- 

 sponse that could be detected even though the nose of the cat 

 was held within 1 cm. of the rats. There was no response from 

 the same group when a week old, nor at ten days. Watson 8 

 thinks that the olfactory tract is entirely unmedullated at this 

 age or for some days later. Our results would seem to indicate 

 that the fear-response takes place before such medullation, then, 

 and certainly before medullation in the higher centres has pro- 

 gressed very far. 



4 Cannon, W. B., Bodily Changes in Pain, Hunger, Fear and Rage, 1915. 

 6 Watson, J. B., Animal Education, 1903, p. 118, and passim. 



