198 SPECIAL HISTOLOGY. 



sections, by splicing 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 papillce, 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 with- 

 out 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 preparation, or by stripping off the outer sheath, be readily re- 

 cognized in all its parts. Caustic soda and potassa acting for a short 

 time, make it still more distinct. The cuticle must particularly be exa- 

 mined 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 application 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 rudi- 

 ments of the hairs will be found. In older embryos, fine sections of the 

 skin must be made ; or the epidermis and the corium may be stripped 

 off together, in which case caustic soda is of assistance. 



Literature. — Eble, " Die Lehre von den Haaren in der gesammten 

 organischen Natur.," 2 Bde., Wein, 1831; Eschricht, " Ueber die 

 Richtung der Haare am menschlichen Korper," in Miill. "Arch.," 1837, 

 p. 37 ; V. Laer, " De structura capill. hum. observationibus microscopicis 

 illustr.," "Dissert, inaug.," Traject. ad Rhenum, 1841, und "Annelin 

 der Chemie u, Pharmacie," Bd. 45, No. 147; G. Simon, " Zur Entwick- 

 lungsgeschchiteder Haare," Miill. "Arch.," 1841, p. 361 ; Krause, article 

 " Haut.," in AVagner's " Handworterbuch d. Phys." 1844, Bd. ii. p. 124 ; 

 Kohlrausch, " Ueber innere Wurzelscheide und Epithelium des Haares," 

 Mull. "Arch.," 1846, p. 300; Jasche, " De telis epithelialibus in genere 

 et de lis vasorum in specie," Dorpat, 1847 ; Kiilliker, " Ueber den Bau 

 der Haarbalge und Haare," in the " Mitthiel d. ziirich., naturf.," Ges., 

 1847, p. 177; Hessling, "Vom Haare und seinen Scheiden in Froriep 

 neue Notizen," 1848, No. 113; Langer, " Ueber den Ilaarwechsel, bei 

 Thieren und beim Menschen," in den " Denkschr. d. Wien," Akad., 

 1850, Bd. i. The comparative anatomy of the hairs is treated of by 

 Heusinger in Meckel's "Arch," 1822, 1823, und "System der Histio- 

 logie;" Erdl, in "Abh.d. Miinch.," Akad., Bd. III. ii. ; Gegenbaur, in 

 " Verhund d. phys. med. Gesellschaft zu Wiirzburg," 1850; Steinlin, in 

 " Zeitschrift, fiir rationellen Medizin," Bd. IX. The allied horny tis- 

 sues are described in the "Dorpat. dissertations," by Brocker, " De 

 textura et formatione spinarum," 1849 ; Hehn, " De text, et form. 

 barbjB Balsenge," 1849 ; Schrenk, " De formatione pennje," 1849. 



