FUNCTION OF VIBRISSAE IN BEHAVIOR OF WHITE RAT 49 



this nerve through the superior cervical and gasserian gangHons 

 There are both dilator and constrictor fibers in this nerve and 

 when one remembers the rich vascular supply to the follicle 

 and the probability that the circulation may be either by way 

 of the sinus or not, one can see that the loss of vaso-motor regu- 

 lation might be functionally serious. But whatever the cause, 

 seven months later when to all appearances from gross dissec- 

 tion the nerve was regenerating and the blood supply normal 

 the vibrissae were still scanty, broken and split. 



Proof of regeneration. All of the animals used in the experi- 

 mentation were killed and carefully dissected after the experi- 

 mentation was over. The time between the operation and this 

 examination ranged from four to seven months. In every 

 instance the nerve had regenerated, but in many cases the number 

 and size of the nerve bundles had decreased. In only one animal 

 did the tactile hairs appear entirely normal. The notes taken 

 of the last three examinations, seven months after the opera- 

 tion, are indicative of the appearance of the dissection. 



Rat 3, male. Vibrissae long and strong, a total of 30 with 

 13 long hairs on the right side, a total of 34 with 12 long hairs 

 on the left side. The nerves on both sides were well regenerated 

 so far as one could tell by inspection. 



Rat 8, female. The vibrissae are almost lacking on the left 

 side. Only a few scanty hairs remain. There are about 20 on 

 the right side, six of which are long. The nerve on the right 

 side has regenerated but is not of the size of a normal nerve. 

 The nerve on the left side is still more imperfectly regenerated. 

 It has only four small bundles and one large bundle of fibers 

 before the anastomosis with the facial. 



Rat 5, female. Vibrissae scanty. On the right there is a 

 total of 18 hairs with eight long and on the left a total of 12 

 hairs with five long. On both sides the nerves have regenerated. 

 The right shows a broad clear white band of fibers, the left 

 nerve is more broken with gaps in its width. 



Tests for sensitivity. In connection with the experimentation 

 tests were made to discover whether the animals retained any 

 sensitivity in the upper lip or tip of nose, to learn what par- 

 ticular kinds of sensitivity if any remained, to find out what 

 orders of sensitivity were connected with the functioning of the 



