1G8 SPECIAL HISTOLOGY. 



[The investigation of the nail-cells and plates is best made 

 in fine sections of recent nails, with and without the addition of 

 reagents, especially caustic soda and sulphuric acid, concerning 

 whose operation the most important points have already been 

 noted. To examine the relations of the parts of the nail to one 

 another and to the epidermis, the nails must be separated from 

 the cutis by maceration, or by boiling in water. It is then 

 seen, that the nail is detached, with the cuticle, from the 

 finger; and in transverse and longitudinal sections, its mode 

 of connection with the former is perceived. The bed of the 

 nail also, its lamina and ridges, the fold and the lamina in the 

 stratum Malpighii of the nail, are easily seen, in this way. Since 

 fine sections, in such a nail, are not readily made, precisely in 

 the most important pai'ts — the margins and root, — it is neces- 

 sary, for this purpose, to employ fresh nails separated from the 

 bone with the cutis, and dried. These afford all the informa- 

 tion required, portions of them swelling up readily in water, 

 and exhibiting the structure of the different layers, with acetic 

 acid and caustic soda, in the most distinct manner.] 



Literature. — A. Lauth, ' Sur la disposition des ongles et des 

 poils/ Mem. de la Societe dTiist. nat. de Strasbourg, 1830-4; 

 Gurlt, ' L T eber die hornigen Gebilde des Menschen u. der 

 Haussaugethiere/ Mull. f Arch./ 1836, p. 26.2 ; Reichert, in 

 Mull. ' Arch./ 1841, Jahresbericht ; O. Kohlrausch, f Recension 

 von Henle's allgem. Anat./ in Gotting. 'Anzeigen/ 1843, p. 24; 

 Rainev, ' On the structure and formation of the nails of the 

 fingers and toes/ in f Trans, of Microsc. Society/ March, 1849 / 

 Berthold, 'Beobachtungen iiber das quantitative Verhaltniss der 

 Nagel- u. Haarbildung beim Menschen, in Mull. 'Arch./ 1850. 



III.— OF THE HAIRS. 



§ 53. 



In every hair we distinguish the free part or shaft, scapus, 

 with its tapering point, from the portion inclosed within the 

 sac, the root, radix. In straight hairs the former is generally 

 straight and rounded ; in the wavy, undulated and somewhat 

 flattened; in the curly and woolly hairs, it is twisted spirally 

 and quite flat or slightly ribbed. The root is always straight, 

 tolerably cylindrical, and softer and thicker than the shaft, at 



