336 



THE SKIN. 



pilla 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 ex- 

 plains 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, from the ultimate ramifications of the cutaneous 

 plexus on which their exquisite sensibility depends. The exact 

 mode in which these nerve-fibres terminate is not yet satisfac- 

 torily determined. 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 fibres appear to terminate, 

 in many of the papillae, by one or more free ends in the sub- 

 stance of a dilated oval-shaped body, not unlike a Paciniau 

 corpuscle (Figs. 136, 137), occupying the principal part of the 

 interior of the papillae, and termed a touch-corpuscle (Fig; 113). 



FIG. 113. 



Papillse from the skin of the hand, freed from the cuticle and exhibiting the tac- 

 tile corpuscles. Magnified 350 diameters. A. Simple papilla with four nerve-fibres: 

 a, tactile corpuscle ; b, nerves. B. Papilla treated with acetic acid : a, cortical layer 

 with cells and fine elastic filaments ; b, tactile corpuscle with transverse nuclei ; c, 

 entering nerve with neurilemma or perineurium ; d, nerve-fibres winding round the 

 corpuscle, c. Papilla viewed from above so as to appear as a cross-section : o, corti- 

 cal layer; b, nerve-fibre; c, sheath of the tactile corpuscle containing nuclei; d, 

 core (after Kolliker). 



The nature of this body is obscure. Kolliker, Huxley, and 

 others, regard it as little else than a mass of fibrous or con- 

 nective tissue, surrounded by elastic fibres, and formed, accord- 

 ing to Huxley, by an increased development of the neurilemma 



