OF THE HAIRS. L99 



grey first at its point or in the middle, and the well-esta- 

 blished instances of its rapidly becoming white, are interesting, 

 and strongly testify to the vitality of the hair; but it has not 

 yet been shown, what peculiar processes in the elements of the 

 hair produce the decoloration of its different pigments. 



As in youth hairs which are shed are replaced by others, so at 

 a later age something similar appears to occur. It is quite 

 certain that during the period of full health and activity, a 

 continual replacement of the numerous hairs which fall out goes 

 on; furthermore that new hairs in great numbers spring up 

 at the time of puberty in certain localities, but the manner in 

 which this takes place is unknown. Inasmuch as eveu in adults 

 we find hair-sacs with little processes downwards, whose proper 

 hair has an abrupt clavateend, as in the child; since further, in 

 this case it not unfrequently happens that tsvo hairs come out of 

 one aperture, and even exist together in one sac; and, finally, 

 since in hairs which have fallen out spontaneously, we invariably 

 find roots like those 1 which exist in the extruded hairs of the 

 first shedding, it may be assumed that an actual shedding of the 

 hairs occurs, even at a later period, in such a manner that the old 

 hair-sacs produce new hairs while they throw off the old ones. I 

 do not, however, intend to affirm by this, that an actual new 

 formation of hairs does not occur after birth, but only this 

 much, that in adults they are certainly regenerated from the 

 already existing hair-sacs, especially if it be recollected that, 

 according to Heusinger's observations, the whiskers of dogs, 

 when pulled out, are reproduced from the same sacs in a few- 

 days, and also that during the shedding of the hair in adult 

 animals, according to Kohlrausch, the young hairs are pro- 

 duced from the old sacs. Also, when the hairs which have fallen 



1 [Henle (' Allg. Anat.,' p. 303) gives a very excellent description of this state of 

 the hair-bull) : " Instead of the soft cellular hair-bulb, we find an inconsiderable 

 elavate enlargement", which is solid and fibrous, like the substance of the shaft, only 

 more clear. From its outer surface, short and irregular processes project downwards, 

 which are prohably the notched lower edges of the outermost layers of the cortical 

 substance; they look like fibres connecting the hair with the Inner wall of the sac. 

 This kind of root is found in hairs which have fallen out spontaneously, and it is, 

 therefore, probable that it belongs to a later stage of development of the hair, or 

 rather marks the conclusion of its development. When the connection with the sac 

 has ceased, which is the case in these elavate roots, the hair grows no longer; 

 probably it is no longer nourished, but falls out." — Eds.] 



