OF THE HAIRS. 197 



nails. 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, Tieflfenbach ("Nonnullade regeneratione ettransplantatione," 

 Herbip, IS'2'2) and Wiesemann (De coalitu partium, Lips. 1824) have 

 succeeded in transplanting the hairs with their sacs. Hairs are deve- 

 loped also in abnormal places, e. g. on mucous membranes, in encysted 

 tumors, 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," 

 Mahori), according to Gruby [" Gaz. He'd.," 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 con- 

 cerned in the production of baldness, which then is limited (Alopecia 

 circumscripta). The process of becoming gray is also obscure, although 

 grief, excessive intellectual 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 Guens- 

 burg and Walther (Miiller's " Archiv," 1844, p. 411, and 1845, p. 34), 

 to arise from & fungus which is developed in the hairs (bulb, shaft), and 

 partly destroys them ; whilst Miinter (ibid., 1845, p. 42) could find no 

 such fungus. This disease, as well as peculiar yellowish-white rings 

 upon the human hairs, consisting of epithelial cells without nuclei 

 (Svitzer, in " Fror. Notizen," 1848, No. 101), which appear to consist 

 of an altered secretion of the sebaceous glands, are less interesting 

 from a histological point of view, and therefore are but shortly adverted 

 to here. 



For microscopic investigation, a white hair with its sac should be 

 chosen in the first instance, subsequently colored ones. Transverse 

 sections may be obtained, either by shaving twice at short intervals 

 (Henle) or by cutting hair on a glass (H. Meyer), or in a bundle be- 

 tween two cards (Bowman), or fixed in a cork (Hartin) ; longitudinal 



