424 



THE SKIN. 



soles of the feet parts, therefore, in which the sense of 

 touch is most acute. On these parts they are disposed 

 in double rows, in parallel curved lines, separated from 

 each other by depressions (fig. 105). Thus they may 

 be seen easily on the palm, whereon each raised line is 

 composed of a double row of papillae, and is intersected by 



lig. 103.* 



Fig. 1044 



short transverse lines or furrows corresponding with the 

 interspaces between the successive pairs of papillae. Over 

 other parts of the skin they are more or less thinly 

 scattered, and are scarcely elevated above the surface. 

 Their average length is about y^^th of an inch, and at 

 their base they measure about ^Q th ^ an ^ nc ^ ' in diameter. 

 Each papilla is abundantly supplied with blood, receiving 

 from the vascular plexus in the cutis one or more minute 

 arterial twigs, which divide into capillary loops in its 

 substance, and then reunite into a minute vein, which 

 passes out at its base. The abundant supply of blood 

 which the papillae thus receive explains the turgescence or 

 kind of erection which they undergo when the circulation 

 through the skin is active. The majority, but not all, of 

 the papillae contain also one or more terminal nerve-fibres, 



* Fig. 103. Papillae, as seen with a microscope, on a portion of the 

 true skin, from which the cuticle has been removed (after Breschet). 



f Fig. 104. 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 Kolliker). 



