OF THE NAILS. L65 



surface of the nail, one behind the other, by piercing it with a 

 needle and colouring with nitrate of silver, they in nowise alter 

 their relative position in the course of the two or three months, 

 during which they are moving towards the point of the nail. 



As to the 'pathological conditions of the nails, they are 

 readily regenerated when they have been detached, in conse- 

 quence of crushing, burning, freezing, cutaneous disorders 

 (scarlet fever, &c), inflammations, exudations, suppurations and 

 effusions of blood in the bed of the nail; in fact, as Pechlin 

 ('Obs. Phys. Med.,' p. 315) narrates, this regeneration may 

 take place periodically ; in a boy, the nails, every autumn 

 became blueish-black and desquamated, together with the 

 epidermis (the horny layer?), and were subsequently regene- 

 rated. In such a case, according to Lauth (' Mem. sur divers 

 points d'Anatomie/ in the 'Annales de la Societe d'Histoire na- 

 turelle de Strasbourg/ t. i, 1834), and Hyrtl ('Anatomie' p. 382), 

 the whole bed of the nail becomes covered by soft horny 

 plates, which harden by degrees, grow into a regular nail, and 

 eventually project with their free edges beyond the end of the 

 finger. "When the last joint of the finger has been lost, 

 rudimentary nails frequently appear upon the back of the 

 second and even of the first phalanx. The older cases are 

 quoted in Pauli ( f De vulneribus sanandis/ Gottingae, 1825, 

 p. 98), more recently Hyrtl (1. c.) saw such a nail 2'" long 

 and 3" broad on the first phalanx of the thumb. As the 

 formation of nail-substance depends upon the vessels of the 

 bed of the nail, we may, with Henle, assume that varying condi- 

 tions of the latter may frequently produce local thickening, 

 thinning, or even detachment of the nail, and that their 

 deformities in cyanosis and phthisis depend on these causes. 

 The thickening and abnormal development of the nails, however, 

 arise very frequently, as I have observed, from a partial ob- 

 struction of the capillaries of their bed. Thus in the lamellated 

 nails of old people, greatly thickened and curved downwards in 

 front, I find all the capillaries of the anterior segment of the 

 bed of the nail closely filled with fat granules of different 

 sizes, and wholly impermeable to the blood ; in such a case 

 the development of nail-substance can take place only in small 

 lamellae in the fold, which then, as mav be readilv understood, 

 are raised up by those which arc growing behind into a con- 



