578 



THE SKIN. 



sition from the epithelia of the rete mucosum into the horny 

 epithelia takes place. 



In the lateral portions of the nail, where papillae are ab- 

 sent, the rete mucosum of the skin, forming the ledge and the 

 furrow, passes into that of the nail through irregular, branch- 

 ing prolongations, which exhibit marked layers of epithelia, more 

 or less endowed with life. In this situation the papillae of the 

 nail are lost, but are replaced by very small and elongated 

 papillae, which belong to the skin and stand in an oblique direc- 

 tion to the rows of the papillae of the nail. A true transverse 

 section through the nail will exhibit within the furrow oblique 

 and transverse sections of the slender papillae of the skin. (See 

 Fig. 244.) 



FIG. 244. IMPLANTATION OF THE NAIL AT ITS BORDER. 



P, papillae, decreasing in size toward the middle line ; B, rete mucosum, which broadens 

 toward the border of the nail, and forms irregular prolongations, .B' / E, epidermal layer of 

 middling consistence ; N, plate of the nail. Magnified 50 diameters. 



The epidermis of the skin produces a pointed prolongation, 

 which overlaps the borders of the nail ; this prolongation is most 

 clearly marked along the posterior border. 



(12) The lacteal glands are accessory formations of the skin. 

 According to C. Langer, who has made careful researches on the 

 development, the structure, and involution of the lacteal glands, 

 they begin to form in the third month of embryonal life, and in 

 the fifth month present radiating tubules, with club-like termina- 

 tions. The tubules open into a shallow depression of the skin, the 



