270 THE HUMAN SOD 7. 



The Papillae of the Dermis, The outer surface of the 

 corium is almost everywhere raised into minute elevations, 

 called papillce, on which the epidermis is molded, so that 

 its deep side presents pits corresponding to the projec- 

 tions of the dermis. In Fig. 75 is shown a papilla of the 

 corium containing a knot of blood-vessels, supplied by the 

 small artery, /, and having the blood carried off from them 

 by the two little veins, gg. Other papillae contain no 

 capillary loops, but, instead, special organs connected with 

 nerve-fibres, and supposed to be concerned in the sense of 

 touch. On the palm of the hand the dermic papillae are 

 especially well developed (as they are in most parts where 

 the sense of touch is acute), and are frequently compound 

 or branched at the tip. On this surface of the hand they 

 are arranged in rows; the epidermis fills up the hollows 

 between the papillae of the same row, but dips down be- 

 tween adjacent rows, and thus are produced the finer epi- 

 dermic ridges seen on the palms.* The wrinkles of old 

 persons are due to the absorption of subcutaneous fat and 

 of other soft parts beneath the skin, which, not shrinking 

 itself to the same extent, is thrown into folds. 



Hairs, longer or shorter, are found all over the surface 

 of the body, except in a few regions, as the palms of the 

 hands and the soles of the feet. A hair is a slender thread 

 of epidermis, developed on a special dermic papilla placed 



What are the papillae of the epidermis? Describe a papilla con- 

 taining blood-vessels. What is found in other papillae? Name a 

 region of the skin where the dermic papillae are especially de- 

 veloped. How are the ridges seen on the palm of the hand pro- 

 duced? To what are the wrinkles on the skin of elderly persons 

 due? 



Name regions of the skin which have no hairs. What is a 

 hair? 



* The more marked furrows on the palm, the so-called " lines of life" of 

 the gypsy's palmistry, have a different origin. 



