THE HAIE. 267 



condition of the hair. Thus it may fall out after sickness, espe- 

 cially from fevers. In old persons, also, it falls out, probably from 

 an obliteration of the vessels of the hair-sacs. 



The process of whitening of the hairs (gray hairs) is very ob- 

 scure. Its immediate cause is chiefly a decoloration of the fibrous 

 portion of the hairs, and an increase of the air- vesicles ; but how 

 this is produced is not understood. Intellectual activity, grief, 

 nervous influences, arid old age, are certainly concerned in it. The 

 rapidity with which this change may be effected, also testifies to the 

 vitality of the hair ; cases having occurred in which it has become 

 gray within a few hours, under the influence of violent emotions. 1 



Dzondi and others have succeeded in transplanting hairs with 

 their sacs. 



The fact that the hairs of the head may become erect under the 

 influence of powerful emotions, is usually associated with the cutis 

 anserina, so called. "We should, however, associate it with the fact 

 established by Eylandt, that the hair-sacs of various parts of the 

 body have smooth muscular fibres inserted into them, and which 

 he has termed the arrectores pili. 



The presence of sulphur in hair accounts for the peculiar odor 

 evolved by its combustion. The various hair-dyes also act by 

 combining with it, and producing a sulphuret of the metal they 

 respectively contain, as silver, manganese, &c. The nitrate of silver 

 is most frequently used (p. 257). 



Pathological States and Developments of the Hair. 



There may be an excessive growth or a falling out of the hairs. 

 They may also be developed in abnormal directions, as is often seen 

 on the head. The} 7 may be found abnormally, on even mucous sur- 

 faces. Hairs have been developed in the intestines, the gall-bladder, 

 in ovarian cysts, in steatomatous and encysted tumors, and in the 

 lungs even. (MoWs case.) They are often largely developed on 

 moles and na3vi. In all these cases they possess sacs and root- 

 sheaths, and in all respects a normal structure. Indeed, since they 



1 A Captain P., of Vermont, was captured by a party of British soldiers in 1813 

 on the Canadian frontier, and put under guard in the evening, with the assurance 

 that he would be shot the next morning. When the appointed time had arrived 

 his hair had entirely changed from a jet black to gray. 



Dr. J. W- Richards, of New York city, mentioned to the author a man whose 

 hair changed from a jet black to gray and back again three times in the course of 

 ten years. No cause could be assigned. He was in perfect health, and not of an 

 excitable temperament, and the change began at the age of thirty-five years. 



