OF THE HAIRS. 201 



instances in the very same manner as that which I have 

 described in children. The reason why the hairs grow con- 

 tinually, if they arc cut, but not otherwise, is the same as 1 have 

 already adduced, to account for the same occurrence in the 

 miils. The vessels of the papilla excrete a certain quantity of 

 nutritive fluid, just so much as is sufficient to keep the whole 

 hair continually moist and in a state of vitality. If the hair be 

 cut, more nutritive fluid is supplied than the hair can use, and 

 therefore it grows by the aid of the superfluity until it has 

 attained its typical length again, or if it be continually cut, it as 

 continually grows. 



Dzondi, Tieffcnbach ('Nonnulla de regenerationc et trans- 

 plantatione/ Herbip, 1822) and Wiesemann (De coalitu partium, 

 Lips. 18.24) have succeeded in transplanting the hairs with their 

 sacs. Hairs are developed also in abnormal places, e. g. on mucous 

 membranes, in encysted tumours, ovarian cysts, and in all 

 these cases, even in the lungs (Mohr's case), possess sacs, root- 

 sheaths, and an otherwise normal structure. No hairs are 

 developed upon cicatrices of the skin. No satisfactory reason 

 can be given for the excessive growth of the hairs, nor for their 

 morbid universal falling out, together with their frequent 

 reproduction in the same way; probably the principal causes 

 are to be found in increased or diminished exudations from the 

 vessels of the papilla and of the hair-sac, and more remotely in 

 the state of the skin and the organism in general. In other 

 cases vegetable productions {fungi) in the interior of the hair 

 itself (in Herpes tonsurans, the " Teigne tondante" Mahon, ac- 

 cording to Gruby ['Gaz. Med./ 1844, No. 14], and Malmsten, 

 (Mull. 'Arch./ 1848, 1), or under the epidermis of the hair and 

 around it (in the Porrigo decalvans of Willan according to 

 Gruby), are concerned in the production of baldness, which 

 then is limited [Alopecia circumscripta). The process of 

 becoming grey is also obscure, although grief, excessive intel- 

 lectual activity, and nervous influences are sometimes evidently 

 concerned in it. It is not until physiology and chemistry have 

 approached these latter processes, that we can hope for a 

 scientific pathology and treatment of the hair. Plica polonica, 

 which, according to Bidder (1. c), is a disease of the shaft of 

 the hair, is said by Guensburg and Walther (Midler's 'Archiv.,' 

 1844, p. til, and 1815, p. 31), to arise from a fungus which 



