BLOOD-VESSELS AND LYMPHATICS OF THE SKIN. 



415 



not alter as growth advances, the impression obtained from the hand of a young child 

 being identical even in the most minute details (although of course somewhat less 

 displayed) with that obtained from the same individual when grown up (F. G-alton). 

 Papillae. The free service of the corium is beset with small eminences thus 

 named, which seem chiefly to contribute to the perfection of the skin as an organ of 

 touch, seeing that they are highly developed where the sense of touch is exquisite. 

 They serve also to extend the surface for the production of the cuticular tissue, and 

 hence are large-sized and numerous under the nail. The papillae are large, and in 

 close array on the palm of the hand and palmar surface of the fingers, and on the 

 corresponding parts of the foot. In these places they are ranged in lines forming the 

 characteristic curvilinear ridges seen when the skin is still covered with its thick 

 epidermis. They are of a conical figure, rounded or blunt at 

 the top and sometimes cleft into two or more points when 

 they are named compound papillae. They are received into 

 corresponding pits on the under-surface of the cuticle. In 



Fig. 472. MAGNIPIKD VIEW OF FOUR OF THE RIDGES OF THE EPIDERMIS, WITH SHORT FUKROWS OR 



NOTCHES ACROSS THEM: ALSO THE OPENINGS OP THE SUDORIFEROUS DUCTS. (After Breschet. ) 



Fig. 473. COMPOUND PAPILLAE FROM THE PALM OF THE HAND, MAGNIFIED 60 DIAMETERS. 



a, basis of a papilla ; b, b, divisions or branches of the same ; c. c, branches belonging to papillae of 

 which the bases are hidden from view. (After Kb'lliker. ) 



structure they resemble the rest of the superficial layer of the corium, and consist 

 of a finely fibrillated tissue, with a few elastic fibres. The bundles of fibrils chiefly 

 run parallel to the axis of the papilla and the fibrils appear to end near its surface, 

 which has a somewhat corrugated aspect. On the palm, sole, and nipple, where 

 they are mostly of the compound variety, they measure from ^^th to y^ th of an 

 inch (0'125 to 0'25 mm.) in height. In the ridges, the larger papillae are placed 

 sometimes in single but more commonly in double rows, with smaller ones between 

 them (fig. 471), that is, also on the ridges, for there are none in the intervening 

 grooves. These ridges are marked at short and tolerably regular intervals with 

 notches or short transverse furrows, in each of which, about its middle, is the minute 

 funnel-shaped orifice of the duct of a sweat-gland (fig. 472). In other parts of the 

 skin endowed with less tactile sensibility, the papillae are broader, shorter, fewer in 

 number, and irregularly scattered. On the face they are reduced to from -g-^ 

 to 5-0-0 of an inch ; and here they at parts disappear altogether, or are replaced by 

 slightly elevated reticular ridges. Fine blood-vessels enter most of the papilla?, 

 forming either simple capillary loops in each, or dividing into two or more capillary 

 branches, according to the size of the papilla and its simple or composite form. 

 Other papillae receive nerves, to be presently noticed. 



Blood-vessels and lymphatics. The arteries divide in the subcutaneous 

 tissue, and, as their branches pass from this deep expansion towards the surface of 

 the skin, they supply offsets to the fat-clusters, sweat-glands, and hair-follicles. 

 They divide and anastomose again near the surface, and at length, on reaching it, 

 form a network of capillaries, with polygonal meshes. Fine looped branches pass 





