SECT. 50.] NAILS. 95 



of all and most easily in perpendicular sections of boiled skin {Henle, 

 Eylandt, Lister). The investigation of the fat-cells is especially instructive 

 in the bodies of lean individuals, in which their membranes and nuclei are 

 easily seen ; in other cases, their membranes can be easily demonstrated by 

 removal of the fat with ether, but the nuclei are with difficulty brought into 

 view by this agent ; they are, however, discovered occasionally here and there, 

 even in full cells. The epidermis, and especially its mucous layer, must be 

 examined fresh, and with acetic acid and diluted caustic soda, in fine perpen- 

 dicular sections ; the horny layer, above all, by the addition of alkalies, in 

 perpendicular and horizontal sections ; but its elements also separate from 

 one another after maceration, and, for the practised observer, are cognisable 

 even in fresh preparations, both when seen from the side and from the 

 surface. 



Literature of the Shin. — Gurlt, in MiiLL. Arch., 1835, P- 399- Simon, JJeoer 

 die Structur der Warzen und uber PigmentHldung in der Maut, in Mull. 

 Arch., 1840, p. 167. Krause, Article limit, in Wagner's Handw. der Physiol., 

 ii. 184.+, p. 127. Kolliker, Znr Entrvickelungsgeschichte der dussern Haut, in 

 Zeitschrift fur Wiss. Zool., Bd. ii. p. 67 ; Histologisehe Bemerkungen, ibid, 

 Bd. ii. p. 1 1 8. Eylaxdt, De Musculis Organids in. Cute Humana Obviis, Dorp. 

 Liv., 1850. J. Lister, Ohs. on, the Muscular Tissue of the Shin, in Quart. 

 Journal of Micr. Science, 1853. On the tactile bodies, see R. Wagner, in 

 MiiLL. Arch., 1852, p. 493 ; Kolliker, in Zeitschr. f. Wiss. Z00L, iv. p. 1 ; G. 

 llEissKER,JBeitrage zur Anatomic und Phys. der Haut, Leipzig, 1853 ; Dalzell, 

 in Monthly Journal. Drawings are given by Berres, tab. vi., vii., xxiv. ; 

 Arnold, Icon. Org. Sens., tab. xi. ; Todd and Bowman, Physiol. Anatomy; 

 Hassall, tab. xxiv., xxvi. ; Kolliker, Mihr. Anut., tab. i. ; and Ecker, Icon. 

 Phys., tab. xvii. 



II. — Of the Nails. 



§ 50. The nails, ungues, are nothing but peculiarly metamor- 

 phosed parts of the epidermis, and, like the latter, may be divided 

 into two layers, viz., a soft mucous layer, and a horny layer, or the 

 nail proper. 



The part of the corium upon which the nail is situated, the led 

 or matrix of the nail, corresponds exactly in form with it, is 

 elongated, quadrangular, arched in the centre, and sloped an- 

 teriorly and posteriorly, but especially on the sides. Its anterior 

 and middle portions are exposed, when the nail with the epidermis 

 is removed by maceration, its lateral borders and posterior part, 

 on the other hand, are concealed by a process of the cutis, the 

 wall of the nail, which is, anteriorly, low and rounded off; pos- 

 teriorly, well defined and longer; and, in conjunction with the bed 

 of the nail, forms a fold, the fold of the nail, which embraces the 

 lateral borders and the posterior part (from 2" to 3'" in extent) of 

 its root. 



