216 



THE SKIN. 



Fk. 143. 



of long standing-, and are then much more conspicuous. Fine blood- 

 vessels enter most of the papilla, forming either simple capillary loops 

 in each, or dividing into two or more capil- 

 lary branches, according to the size of the 

 papilla and its simple or composite form, which 

 turn round in form of loops and return to the 

 veins. Other papillae receive nerves, to be 

 presently noticed. 



Blood-vessels and lymphatics. — The blood- 

 vessels divide into branches in the subcutaneous 

 tissue, and, as they enter the skin, supply capil- 

 lary plexuses to the fat-clusters, sweat-glands, 

 and hair-follicles. They divide and anastomose 

 still further as they approach the surface, and 

 at length, on reaching it, form a dense network 

 of capillaries, with rounded pergonal meshes. 

 Fine branches are seen in the papillte. as 

 already mentioned. The lymphatics are abundant 

 and large in some parts of the skin, as on the 

 scrotum and round the nipple; whether they 

 are equally so in all parts may be doubted. 

 They form networks, which become finer as they 

 approach the surface, and communicate under- 

 neath with straight vessels, and these, after a 

 longer or a shorter course, join larger ones or 

 enter lymphatic glands. The finest and most 

 superficial network, although close to the surface 

 of the corium, is beneath the net of superficial 

 blood-capillaries ; in certain parts on the palm and sole, lymphatics 

 pass into the papillEe, but do not reach their summits. Besides these 

 plexuses, other lymphatics accompany the blood-vessels to which 

 they are applied, two passing commonly to each, and joining and anas- 

 tomosing over the vessel. 



Nerves. — Nerves are supplied in very different proportions to 

 different regions of the skin, and according to the degree of sensibility. 

 They pass upwards towards the papillary surface, where they form 

 plexuses, of which the meshes become closer as they approach the sur- 

 face, and the constituent branches finer. From the most superficial plexus 

 which lies immediately under the epithelium, delicate non-medullated 

 fibrils have been traced passing upwards amongst the cells of the Malpi- 

 ghian layer of the cuticle, where they end, according to some accounts, in 

 slightly bulbous free extremities ; according to others, in a plexus of 

 excessively fine fibrils. A large share of the cutaneous nerves is distri- 

 buted to the hair-follicles, whilst some end in special terminal organs, 

 namely, end-hidhs, iactile corjniscJes, and Pacinian hodies. The last- 

 named lx)dies are seated in the subcutaneous tissue. End-bulbs are 

 found on the glans penis and glans clitoridis, and in some of the papili[B 

 on the red border of the lips. The tactile corpuscles of the skin are 

 more numerous ; they are found in certain papillre of the palm and 

 sole, more sparingly in those of the back of the hand and foot, the 

 palmar surface of'the fore-arm, and the nipple. Such papilliB commonly 

 contain no blood-vessels, and are named "tactile," (fig. 144, h), as dis- 

 tinguished from the "vascular" papilla («). Sometimes, however, a 



Fig. 143. — Magxified 

 View op four of the 

 eldges of the epider- 

 mis, caused by rows op 

 papillie beneath, with 

 SHORT Furrows or 

 Notches across them : 

 also the Openings 

 OP the Sudoriferous 

 Ducts (after Brescliet). 



