THE SKIN. 279 



glands, sweat-ducts, nerves, lymphatic vessels, and non-striated 

 muscles are also present in this layer. For a fuller descrip- 

 tion of the intimate structure of the connective-tissue bundles 

 and cells, see the subject of connective tissues. 



Blood-vessels. Only the corium and subcutaneous tissue 

 are provided with blood-vessels. The arterial blood-vessels 

 supplying the skin form two parallel horizontal layers, a su- 

 perficial and a deep one. The deep layer lies in the subcuta- 

 neous tissue, and consists of large vessels running parallel to 

 the general surface. From this horizontally lying deep layer, 

 branches are distributed to the sweat-glands and fat-follicles of 

 this region. The principal branches, however, pass perpendicu- 

 larly or obliquely upward through the corium to its upper part, 

 and form immediately beneath the papillae (after free branch- 

 ing and anastomosis) a superficial horizontal layer, the stratum 

 subpapillare. From the vessels ascending 

 through the corium branches are given off to 

 the hair-follicles, sebaceous glands, and gen- 

 eral tissue of the corium. From the stratum 

 subpapillare small branches pass upward into 

 the papillse, where they become capillary ves- 

 sels, which proceed to the summit of the 

 papilla. (See Fig. 119.) Before reaching this point, however, 

 they frequently divide into two or more branches. Frequently, 

 those papillse in which tactile corpuscles are seated have no 

 blood-vessels. 



The veins are arranged on the same plan as the arteries : 

 they form a superficial and a deep layer, and have their origin 

 in the papillae. From the superficial layer larger vessels pass 

 downward, receiving blood from the veins of the hair-follicles, 

 sebaceous glands, and the general tissue of the corium, thus 

 forming a deep subcutaneous layer or venous network. 



Nerves. Medullated and non-medullated nerve-fibres are 

 present in the skin. They are found in combination in the nerve- 

 trunks of the subcutaneous tissue, the medullated fibres being 

 most numerous in those regions of the skin where the Pacinian 

 and tactile corpuscles are most abundant. In the subcuta- 

 neous connective-tissue region, and in the lower part of the 

 corium, some nerve-fibres leave the nerve-trunks and pass to 

 the glands, blood-vessels, and Pacinian corpuscles found in this 

 region. In the corium some of the fibres lose their medullary 



