THE STKUCTURK AND FUNCTIONS OF THE SKIN. 



of which it thus forms a kind of mould. Besides affording by its imper- 

 meability a check to undue evaporation from the skin, and providing the 

 sensitive cutis with a protecting investment, the cuticle is of service in 

 relation to the sense of touch. For by being thickest in the spaces,' be- 

 tween the papillae, and only thinly spread over the summits of these pro- 

 cesses, it may serve to subdivide the sentient surface of the skin into a 

 number of isolated points, each of which is capable of receiving a dis- 

 tinct impression from an external body. By covering the papillae it ren- 

 ders the sensation produced by external bodies more obtuse, and in this 

 manner also is subservient to touch: for unless the very sensitive papillae 

 were thus defended, the contact of substances would give rise to pain, 

 instead of the ordinary impressions of touch. This is shown in the ex- 



FIG. 241. Vertical transverse section through a small portion of the nail and matrix largely- 

 magnified. A, corium of the nail-bed, raised into ridges or laminae a, fitting in between correspond- 

 ing laminse 6, of the nail. J9, Malpighian, and C, horny layer of nail; d, deepest and vertical cells; 

 , upper flattened cells of Malpighian layer. (Kolliker.) 



treme sensitiveness and loss of tactile power in a part of the skin when 

 deprived of its epidermis. If the cuticle is very thick, however, as on 

 the heel, touch becomes imperfect, or is lost. 



(3.) The Skin is aivorgan of Secretion, as it possesses Seba- 

 ceous Glands. The secretion of the sebaceous glands and hair-follicles 

 (for their products cannot be separated) consists of cast-off epithelium 

 cells, with nuclei and granules, together with an oily matter, extractive 

 matter, and stearin ; in certain parts, also, it is mixed with a peculiar 

 odorous principle, which contains caproic, butyric, and rutic acids. -It is, 

 perhaps, nearly similar in composition to the unctuous coating, or vernix 

 caseosa, which is formed on the body of the foetus while in the uterus, 

 and which contains large quantities of ordinary fat. Its purpose seems 



