290 ELEMENTS OF HISTOLOGY. [Chap, xxxiv. 



(b) Then there is the vascular system of the hair- 

 follicles. The papilla has a capillary loop, or rather 

 a minute arteriole, a capillary loop, and a descending 

 vein, and the fibrous tissue of the hair-sac possesses 

 capillaries arranged as a network with elongated 

 meshes, with its afferent arteriole and efferent vein. 



(c) The sebaceous follicle has its afferent arteriole 

 and efferent vein, and capillary networks surrounding 

 the alveoli of the gland. The arrector pili and other 

 bundles of non-striped muscular tissue possess capil- 

 lary networks with elongated meshes. 



(d) The sweat-glands have an afferent arteriole, 

 from which proceeds a very rich network of capil- 

 laries, twining and twisting round the gland-tube. 

 The duct possesses its separate afferent arteriole and 

 capillaries, forming elongated meshes. 



(e) The last arterial branches are those that reach 

 the surface of the corium, and there break up into a 

 dense capillary network with loops for the papillae. 

 In connection with these capillaries is a rich plexus of 

 veins in the superficial layer of the corium. 



(jQ In the na,il-bed are dense networks of capil- 

 laries, with loops for the above-named folds. 



397. The lymphatics. There are networks of 

 lymphatic vessels in all strata of the skin ; they are, 

 more or less, of horizontal expansion, with oblique 

 branches passing between them. Their wall is a 

 single layer of endothelial cells, and some of them 

 possess valves. Those of the surface of the corium 

 take up lymphatics of the papillae. The subcutaneous 

 lymphatics are the biggest. The fat tissue, the sweat- 

 glands, and the hair-follicles possess their own lym- 

 phatic clefts and sinuses. The interfascicular spaces 

 of the corium and subcutaneous tissue are directly 

 continuous with the lymphatic vessels in these 

 parts. 



398. The nerves. The nerve-branches break up 



