THE SKIN AND ITS SECKETIONS. 503 



distributed in other portions of the organism. Further, 

 bile contains fatty acids ; an organic base cholin ; and 

 undetermined extract-like organic substances. 



Thoroughly dried bile leaves behind after combus- 

 tion, about 12 per cent, of ashes, consisting of the 

 sodium, potassium, calcium, and iron salts of sulphu- 

 ric, phosphoric, and carbonic acids, and of chlorine. 



7. The Skin and its Secretions. 

 Horny Tissue. 



The general covering of the body consists of the 

 scarf-skin (cutis, epidermis] and the corium (cutis verd). 



The epidermis is a horny layer without bloodvessels. 

 It consists of microscopical flat cells, closely joined 

 together. Under this on the corium lies a softer layer 

 of spherical cells (rete Malpighii), without doubt un- 

 hardened epidermis substance. 



The corium is a solid, elastic skin supplied with 

 bloodvessels, composed of strong, interlacing, fibrous 

 bands. Under it lies the subcutaneous areolar tissue, 

 in which are contained the two kinds of small cutane- 

 ous glands, which secrete the fluid perspiration, and 

 the sebaceous matter of the skin. The excretory ducts 

 of the first kind open into the pores of the epidermis, 

 those of the other into the hair-follicles. In addition 

 to these excretions a quantity of water, with some car- 

 bonic acid, is given off through the skin in gaseous 

 form according to purely physical laws. 



"When boiled for a long time with water, the corium 

 is converted into gelatin, and is dissolved (see p. 508, 

 Gelatinous Tissues). On cooling, this solution congeals, 

 forming a jelly. This transformation is also brought 

 about more rapidly by acids. Immersed in a solution 

 of basic iron sulphate or of mercury chloride, the skin 

 combines with these salts, and then does not decay. It 

 possesses the greatest affinity for tannic acid, which it 

 takes up from vegetable infusions containing the acid, 

 and with which it forms a compound (apparently 

 merely mechanical) insoluble in water, and not under- 



