202 SPECIAL HISTOLOGY. 



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 f 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 coloured 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 between two cards (Bowman), or fixed in a cork 

 (Harting); longitudinal sections, by slicing a finer or splitting 

 a coarser hair. The hair-sacs may be examined, both isolated 

 and with the hair ; their different layers may be separated by 

 preparations, and the nuclei of the external ones may be 

 demonstrated by acetic acid. Concerning the papilla, all that 

 is necessary has been said above; the whole upper part of the 

 root-sheath generally follows the hair when it is torn out, and 

 in the macerated skin it comes out very readily with the hair: 

 its cells may be made out without addition, or by a little acetic 

 acid or caustic soda. The inner root-sheath is often to be 

 found entire in torn out-hairs, and may without further prepa- 

 ration, or by stripping oft' the outer sheath, be readily 

 recognised in all its parts. Caustic soda and potass acting 

 for a short time, make it still more distinct. The cuticle 

 must particularly be examined with alkalies and sulphuric acid, 

 like the hair itself. The most important details upon this 

 point have already been given, and more may be found in 

 Donders (1. c). I will only add that in this case also, the applica- 

 tion of a high temperature (see above, in the section on the nails) 

 saves much time. In investigating foetal hairs, in the very 

 young state it is sufficient to tear off the epidermis, attached to 

 which the rudiments of the hairs will be found. In older 

 embryos fine sections of the skin must be made; or the epidermis, 

 and the coriura may be stripped off together, in which case 

 caustic soda is of assistance. 



Literature. — Eblc, 'Die Lehre von den Haaren in der 

 gesammten organischen Natur./ 2 Bde., Wien, 1831 ; Esch- 



