416 



THE SKIN. 



from the superficial arteries into the papillae, as already mentioned. The veins 

 closely accompany the arteries. 



Lymphatics are found in all parts, although probably not everywhere in equal 

 number ; they are abundant and large in some parts of the skin, as on the scrotum 

 and round the nipple. They form at least two networks, one superficial and another 

 more deeply situated, which intercommunicate by uniting vessels, whilst the deeper 

 network joins the lymphatics of the subcutaneous tissue. According to Klein 

 there is a continuous plexus through the whole thickness of the corium, and all the 

 vessels possess valves. The most superficial network, although close to the surface 

 of the corium, is beneath the net of superficial blood-capillaries, which are much 

 smaller than the lymphatic capillaries. In certain parts on the palm and sole 

 lymphatics pass into the papillas, but do not reach their summits. Other lymphatics- 

 accompany the blood-vessels, two passing commonly with each small artery and 

 vein, and joining and anastomosing over the vessels. 



As in other kinds of connective tissue, the lymphatics of the skin may be said to originate 

 in the cell-spaces of the tissue, and since the cells lie for the most part in rows between the 

 bundles, the combined spaces form interfascicular clefts which can be injected with the lym- 

 phatics. The superficial cell-spaces communicate with the intercellular channels of the 

 epithelium, and thus these also are brought into connection with the lymphatics. The cell- 

 spaces of the adipose tissue can similarly be injected. 



Nerves. Fine varicose nerve-fibrils pass up into the epidermis, penetrating- 

 between the cells of the Malpighian layer (fig. 474), where they undergo a cer- 



Fig. 474. SUCTION OF EPIDERMIS 



FROM THE HUMAN HAND. HlGHLT 



MAGNIFIED. (Ranvier. ) 



//, horny layer, consisting of s t 

 superficial horny scales ; sw, swollen- 

 out horny cells'; s.l, stratum lucidum; 

 M, rete mucosum or Malpighian layer, 

 consisting of p, prickle-cells, several 

 rows deep ; and c, elongated cells 

 forming a single stratum near the 

 corium ; n, part of a plexus of 

 nerve-fibres in the superficial layer 

 of the cutis vera. From this, 

 plexus, fine varicose nerve-fibrils, 

 may be traced passing up be- 

 tween the cells of the Malpighiaa 

 layer. 



tain amount of ramification. 

 The branches do not unite 

 with one another to form a 

 network, but end in knob- 

 like swellings or varicosi- 

 c ties. With the growth and 

 displacement of the cells be- 

 tween which they are placed, 

 these varicosities become, ac- 

 cording to Ranvier, continu- 

 ally detached from the end of the fibrils, the latter meanwhile growing constantly 

 to supply the place of the detached portions. 



In the skin covering the snout of certain animals (e.g. mole) the nerves end in peculiar 

 terminal organs (Eimer), formed of thickenings of the epidermis, the nerve-fibres passing as- 

 an elongated bunch of closely set, somewhat zigzag, varicose, unbranched fibrils between the 

 epidermis-cells. Besides these fibrils there are others at the periphery of the organ which are 



