48 STELLA BURNHAM VINCENT 



mentation were ready for use and save for a thinness of fur 

 over the nose they could not be told from the others which 

 were used at the same time as controls. 



Three of these rats were afterward killed and by dissection 

 and by tissue stained by the Marchi method we were furnished 

 with proofs of section as well as of the certain distribution of 

 this nerve. 



Trophic functions. In view of the fact that trophic function 

 of nerves is much discussed at present there may be some in- 

 terest felt in the following phenomena. About ten days after 

 the section of the nerve the vibrissae were noticed to be curling 

 and splitting and breaking. They felt rough and dry to the 

 touch and appeared rough and uneven on close inspection. They 

 pulled out easily, the animal showing no apparent signs of pain 

 and many of them were more brittle and broke far more easily 

 than ordinarily. The animals washed their faces as diligently 

 as ever so that this condition could not have resulted from lack 

 of care. As old hairs sometimes persist in the follicle for a year 

 after they are really dead, even while the new ones are growing 

 up beside them, the rats were at no time without these appen- 

 dages but they were noticeably shortened in length and fewer 

 in number. It may be argued that the effect upon the hair was 

 due to the interference with the blood supply and not to the 

 loss of innervation. The reply would be that while this may 

 be true, the hemorrhage was slight, as was stated before, the 

 follicles themselves were intact, the wound had healed and the 

 dressing was off in two weeks while the effect upon the hairs 

 was seen months later even after the nerves had begun to re- 

 generate. Surely such prolonged effects could not be a result 

 of the disturbance of the arterial supply in the course of the 

 operation. The hairs lengthen very rapidly. I do not know 

 how long it would take a new hair to grow from the follicle to 

 its full size but in the use of rats upon the maze, where the 

 hairs were kept clipped close they had to be cut twice a week 

 to prevent their being dragged upon the path. 



It might be, however, that the eff'ect upon the hairs was caused 

 by a vaso-motor derangement. It will be remembered that the 

 trigeminus contains vaso-motor fibers which originate in the 

 third, fourth and fifth roots of the spinal cord and which reach 



