FUNCTION OF VIBRISSAE IN BEHAVIOR OF WHITE RAT 41 



7. The hairs projecting from the side also mediate guiding 

 sensations as they sweep a vertical surface or are turned down 

 against an edge as an animal runs. They keep it in the safe path. 



8. They are, presumably, an important external element in 

 rightness and leftness and hence closely associated with those 

 kinaesthetic sensations which control an animal's turning. 



9. As exquisitely sensitive mobile organs they are an effec- 

 tive aid to those kinaesthetic sensations functioning in loco- 

 motion by giving exactness to the place of the turn. 



10. They are so evolved in this animal to supplement an 

 exceedingly defective vision. 



11. So long as an animal's efforts are engrossingly engaged 

 in maintaining its own equilibrium all efforts to acquire other 

 cooordinations will be rendered increasingly difficult. 



I. The Sense of Equilibrium 



One of the most significant things revealed in the course of 

 this study was the number and distribution of the slips and 

 falls of the animals. To our suiprise they were not nearly so 

 many as we had expected from the narrow, elevated, unpro- 

 tected runways. The maze was low, and what falls there were 

 did not seem to affect the animals seriously. They were always 

 picked up, put on the maze at the point from which they fell 

 and for the most part at once began to run anew and often 

 finished the ran without error. The time lost was so brief it 

 was not even counted out in the records. 



As was remarked before, these slips and falls were made from 

 both the sides and the open ends of the runways but in far 

 greater numbers from the sides. The normal rats had few 

 accidents but those with the nerve cut and those whose vibrissae 

 were cut from birth had five times as many. The blind animals 

 were only at a slight disadvantage in this respect. It might be 

 concluded, therefore, that the vibrissae are of much more im- 

 portance to the rat in such a situation like this than vision. 

 But when we look at the record of the rats without either vision 

 or vibrissae we infer that one of these sense organs at least is 

 necessary for the acquiring of this coordination. 



Such accidents as have been described might have different 

 causes. First, they might come from rapid or careless running. 

 In the normal rats so far as could be seen this was the case. 



