FUNCTION OF VIBRISSAE IN BEHAVIOR OF WHITE RAT 45 



moves in a circle. If this disturbance increases the head is 

 finally pulled back so that in resting it is turned toward the 

 hind part of the body while its fore legs are extended forward 

 in a characteristic fashion as if to brace the animal. If stimu- 

 lated now the animal rolls, it can no longer walk. If picked 

 up by the tail it revolves on its long axis. Whether this trouble 

 is due to internal ear or to cerebellar trouble I do not know, 

 nor whether it has one or several causes. 



If a rat falls from the maze or from the table as frequently 

 happens, it begins to whirl. This may continue for only a brief 

 period or it may last half an hour, but it is the common effect 

 of a blow or fall of any kind. The reason for this is for pathol- 

 ogists to determine but the facts are as stated. 



Wesley Mills and others have made much of what they are 

 pleased to call the "sense of support" in animals. They do not 

 mean, as I understand them, a distinct sense, but a fundamental 

 complex of muscle and joint senses with stereognostic senses 

 which function in certain definite ways and which may be 

 observed chiefly through its disturbance. Mills says, speaking 

 of the behavior of young puppies the day of birth: — "It would 

 seem that there is no more urgent psychical necessity to young 

 mammals than this sense of being supported. All their ances- 

 tral experiences have been associated with terra firma so that 

 it is not very surprising that when terra firma seems about to 

 be removed they are so much disturbed." '' 



Mr. Yerkes later made this the subject of some experimenta- 

 tion in space perception and concludes from some tests when 

 blindfolded that vision is the important factor in the space 

 perception of tortoises. He found the same hesitancy at the 

 edges of elevated surfaces which increased from strictly water 

 forms to land forms. The hesitation also appeared at much 

 less height for land forms than for water forms. When blind- 

 folded the water forms usually ventured from any height with- 

 out hesitation, apparently having no tactual-kinaesthetic sen- 

 sations from skin, muscles and joints strong enough to cause 

 an inhibition of the movement. The land- water forms on the 

 contrary turned back from the edge and would not leave a 

 board from which they would have flung themselves under 



'* Mills, W.: The Psychic Development of Young Animals and Its Physical 

 Correlate, Trans. Roy. Soc. Canada, 1894, sec. IV, p. 50. 



