CUTANEOUS RESPIRATION. CUTANEOUS SECRETION: 533 



of fluid from the vessels of the skin. Portions of skin deprived of epi- 

 dermis, therefore, appear reddened, and exude droplets of moisture. 

 Large weeping areas of skin are capable of impairing considerably the 

 nutritive state of the body through loss of albumin. The epidermis and 

 the epidermoidal structures are, further, when dry, poor conductors of 

 electricity. The passage of a strong current diminishes this resistance 

 to one-thirtieth, in consequence of cataphoric infiltration. Finally, it 

 may be stated that the presence of the uninjured epidermis protects 

 adjacent parts against adhesion. 



As the epidermis is but slightly extensible, it is drawn tensely over the folds 

 and papillae of the corium, which are obliterated on stretching the skin. Even 

 the papillae disappear in this way, if the tension is considerable. 



The hairs serve in various situations as tactile organs eye-lashes, lanugo- 

 hair of the face; and upon the head, as a poor conductor of heat, they regulate the 

 taking up and the giving off of heat and afford protection against direct radia- 

 tion from the sun. 



CUTANEOUS RESPIRATION. CUTANEOUS SECRETION. 



SEBUM. SWEAT. PIGMENT-FORMATION. 



The secretory activity of the external integument, whose extent ex- 

 ceeds more than one and a half square meters, comprises (i) the respi- 

 ratory excretion; (2) the secretion of the cutaneous fat; and (3) the 

 secretion of sweat. 



Cutaneous respiration has already been discussed (p. 241). 



Suppression of the activity of the skin, by varnishing is followed, in warm- 

 blooded animals, at first by no reduction in the total gaseous interchange. Proba- 

 bly increased respiratory activity on the part of the lungs compensates for the 

 loss of the respiratory activity of the skin. In certain mammals, especially in 

 rabbits, death results from varnishing of the skin, probably in consequence of 

 excessive loss of heat. Strong animals die later than weak; horses only in the 

 course of several days, with trembling and emaciation. The greater the area of 

 skin that is not varnished, the later does death take place. Rabbits die after 

 one-eighth of the surface of their body has been varnished ; and after total covering 

 of the skin the temperature at once declines, to as low as 19. Pulse and respira- 

 tion generally become less frequent ; but with circumscribed varnishing, increased 

 respiratory frequency and increased excretion of urea have been observed. Swine, 

 dogs, and horses are said to exhibit only transitory depression of temperature 

 and languor after one-half of the surface of the body has been varnished, though 

 life is preserved. Varnishing of the skin is not injurious to human beings. 



The sebum of the skin. The fat secreted by the sebaceous glands 

 is fluid when discharged, but stagnating within the excretory duct of the 

 gland it is transformed into a white, tallowy mass, which, principally 

 on the alae of the nose, can be expressed in sausage-shaped comedones. 

 Its function is to keep the epidermis and the hair pliable and to pro- 

 tect the skin against excessive desiccation. Microscopically, the secre- 

 tion contains innumerable fat -globules, a few gland-cells filled with fat 

 and rendered visible on addition of sodium hydrate, and in almost all 

 human beings microscopic mite-like animals demodex folliculorum. 



Chemical examination demonstrates the' presence principally of fats, particu- 

 larly olein (fluid) and palmitin (solid), together with fatty soaps, and some choles- 

 terin; in addition, a small amount of albumin and unknown extractives. Among 

 the inorganic constituents, the insoluble earthv phosphates preponderate; while 

 the alkaline chlorids and phosphates are subordinate. There is some doubt as to 

 the occurrence of sodium and ammonium phosphate and of ammonium chlorid. 



