PART II.] 



Structure of Healthy Skin. 



423 



with Fig. 22 on next page, which represents the changes which occur in the different 

 parts of the skin in Delhi sore. 



The letters a, 6, c correspond to the three principal layers of which the skin 

 consists. The horny (a) and the mucous layers (6) of the epidermis form what is 

 usually implied by the cuticle ; the upper layer consists of hardened epidermic scales, 

 and follows a course almost parallel to the surface, but the lower layer not only 

 consists of more distinctly cellular elements (the prickly-cog-wheel aspect of a great 



Fig. 21. — A Vertical Section of Healthy Skin x (50. 

 (Sketched from three preparations, with a camera lucida.) 

 a, Horny, and h. Mucous layer {Itete MalpigMt) of the Epidermis ; c, Papillary layer of Corium (<Z, d) ; 

 e, Hair ; /, Hair follicle ; g, Duct of sweat gland (^;) ; h, Sebaceous gland ; /", Blood-vessel sending 

 up branches to papillae (c) ; ,;, Arrector pili ; It, Section of vessels with their surrounding adventitia ; 

 I, Delicate fibrous tissues continuous with adventitia of blood-vessels and lymphatics ; m, Section of 

 sudoriparous duct and blood-vessels ; n, Areolar tissue and fat cells ; 0, Section of vessels within the 

 capsule (^) of the convoluted portion of sweat gland {j)) ; r, Blood-vessel filled with corpuscles, giving 

 off a twig to the root of the hair. 



portion of these cells cannot be represented in a drawing made on so small a scale as 

 this), but also forms a coating to the projections of the true skin or cutis vera (d) 

 termed papillae (c). Into the latter nutritive vessels {i) and nerves penetrate. The 

 epidermic layer — the mucous portion of it especially — not only dips between the 

 papillae for the purpose of supplying them with a covering, but also dips still more 

 deeply into the tissue of the true skin, and thus aids in forming to a greater or less 

 degree the walls of all the tubular structures which open on the surface of the body. 

 These are hair- (/) and sebaceous follicles (^), and the ducts of the sweat glands (^). 



