KIDNEYS, SKIN, AND GENERAL EXCRETION. 399 



fingers and the palm of the hand. These furrows are prob- 

 ably not alike in any two individuals . When once formed 



Fig. 133. SECTION OF THE HUMAN EPIDERMIS, SHOWING TWO VASCULAR PAPILLA BE- 

 NEATH. (After Heitzmann.) 

 BP, loop of capillaries; Dp, duct of sweat gland; EB horny layer of epidermis; PL, 



stratum lucidum; V, Malpighian layers of epidermis. 



they never change, the impressions of the furrows on an 

 infant's thumb being identical with the impression of the 

 same thumb in old age. In some countries impressions are 

 made of the furrows of the fingers or thumbs of criminals 

 in order that they may keep a perfectly trustworthy de- 

 scription of them, it being impossible for the criminal to 

 change this part of his personal appearance. The absolute 

 correspondence of an impression so taken at any time and 

 the thumb offered in evidence would be incontrovertible 

 proof of the identity of the man. These papillae while 

 present over nearly all portions of the skin are especially 

 plentiful in those portions of the body where the sense of 

 touch is peculiarly acute. 



Through the corium run the blood-vessels, veins and 

 capillaries. The epidermis has no direct vascular supply, 

 although the tips of capillary loops do sometimes reach 

 slightly beyond the Malpighian layer. The epidermis is 

 therefore obliged to draw its nourishment from the lymph 



