OF THE NAILS. 153 



tions, to which acetic acid and dilute solution of soda may be 

 added ; the horny layer, particularly by the addition of alkalies, 

 in perpendicular and horizontal sections; however, mere mace- 

 ration in water separates its elements from one another, and 

 those who arc practised can discover them in fresh preparations, 

 when viewed both laterally and from the surface.] 



Literature. — Gurlt, ' Vergleichende Unters. uber die Haut 

 des Menschen u. d. Haus-saugethiere/ &c. in Mull. ' Archiv/ 

 1835, p. 399 (good figures for the period) ; Raschkow, ' Mele- 

 temata circa Mammal, dentium evolutionem/ Vratisl, 1835 

 (first more complete description of the elements of the epider- 

 mis under Purkinje's guidance) ; Simon, ' Ueber die Structur 

 der Warzen u. uber Pigmentbildung in der Haut/ Miill. 

 ' Arch./ 1840, p. 167 (pigment-cells in the rete of white per- 

 sons) ; Krause, article ' Haut/ in Wagner's ' Handworterbuch/ 

 II, 1841, p. 127 (a detailed and excellent treatise) ; Kollikcr, 

 ' Zur Entwicklungsgeschichte der aussern Haut/ in 'Zeitschrift 

 fiir wiss. Zool./ Bd. II, p. 67 ; ' Histological Observations/ ibid. 

 II, p. 118; Eylandt, ' De musculis organicis in cute human.i 

 obviis/ Dorp. Liv., 1850. Besides these, refer particularly to 

 the works of Simon (' Die Hautkrankheiten durch anatomische 

 Untersuchungen erlautert/ 2 Aufll., Berl., 1851) ; Von Biiren- 

 sprung ( { Beitrage zur Anat. u. Pathol, der menschlichen 

 Haut/ 1848) ; and Kramer (' Ueber Condylome u. Warzen/ 

 Gotting., 1847). Figures are given by R. Wagner, ' Icon, 

 phys./ Berres, tab. vi, vii, xxiv (middling, with the exception 

 of what regards the vessels) ; Arnold, ' Icones org. sens./ 

 tab. xi (very pretty, but drawn with too low magnifying 

 powers) ; Hassall, tab. xxiv, xxvi, xxvii (among others, the skin 

 of the negro also, and the areola of the white from within, 

 coloured) ; and myself, ' Mikr. Anatomie/ Taf. i. 



II.— OF THE NAILS. 



§ 48. 



The nails, ungues, are nothing but peculiarly metamorphosed 

 parts of the epidermis, and like it, they consist of two 

 layers, — of a soft mucous-, and a horny layer, or the proper 

 nail. 



