336 



HAND-BOOK OF PHYSIOLOGY. 



they measure about ^J-g- of an inch in diameter. Each papilla is abun- 

 dantly 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 



FIG. 228. Vertical section of skin. A. Sebaceous gland opening into hair-follicle. B. Muscular 

 fibres. C. Sudoriferous or sweat-gland. D. Subcutaneous fat. E. Fundus of hair-follicle, with hair- 

 papillae. (Klein and Noble Smith.) 



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

 ultimate ramifications of the cutaneous plexus, on which their exquisite 

 sensibility depends. 



Nerve-terminations. In some parts, especially those in which the 

 sense of touch is highly developed, as, for example, the palm of the hand 

 and the lips, the nerve-fibres appear to terminate, in many of the papillae, 

 by one or more free ends in the substance of an oval-shaped body, occupy- 

 ing the principal part of the interior of the papillae, and termed a touch- 



