FUNCTION OF VIBRISSAE IN BEHAVIOR OF WHITE RAT 51 



them are split on the end. Tested the Hp with a hot point but 

 got no reaction. The animal squealed every time it was touched 

 posterior to the vibrissae. 



Oct. 2, (20 days). Other hairs are now breaking and curling. 

 There is no apparent sensitivity to pain, touch or warmth in 

 the upper lip in the neighborhood of the vibrissae but the animal 

 always winces when the under lip or interior of the nares is 

 touched. He shows no sign of feeling deep pressure. 



Oct. 14, (32 days). Still more hairs breaking and splitting. 

 These hairs feel rough to the touch. Tested by pulling and 

 pushing hairs, for light touch and deep pressure, for pain and 

 for warmth and cold but found no signs of any sensitivity. 



Oct. 24, (42 days). Same as Oct. 14. No signs of any sensa- 

 tion yet. Wound perfectly healed. 



Nov. 23, (72 days). Tested with needle, pulling hairs, press- 

 ing cheek, and with hot points. There was some slight sensi- 

 tivity on the upper part of the cheek. The upper row of hairs 

 was still insensitive to pulling but the needle and hot point 

 evoked reactions. The tip of the nose gave evidence of sensi- 

 tivity occasionally but much less often than the parts men- 

 tioned. The reaction to the hot point was probably pain as the 

 point was hot enough to be painful when tested on human skin 

 and as it cooled there was no reaction perceptible. The normal 

 animal objects to having these sensitive parts of his body touched 

 and nearly always responds by a quick jerk but these animals 

 have permitted themselves to be tested freely and are only now 

 objecting. There is no way to know whether they are respond- 

 ing to touch or to temperature unless they react to the one 

 when they do not to the other. In this case it is only the extremes 

 of temperature to which they respond and to pain with the possi- 

 bility that the heat reaction may also be pain. 



Dec. 9, (12 weeks). Reacts to heat (probably pain), and to 

 cold in the two upper rows of vibrissae. Seems to be hyper- 

 sensitive to hard pressure. The right side is more sensitive 

 than the left. 



Dec. 20, (14 weeks). Same as above. The point must be 

 hot to get the reaction and in using ice it was fully 30 seconds 

 before the flinching was seen- There is hypersensitiveness to 

 deep pressure and to needle prick. In most cases the animal 

 does not show any signs of feeling when a hair is pulled out. 



