CHAPTER XVII. 



ELIMINATION CONCLUDED: THE SKIN. NAILS AND HAIR. 

 BODILY HEAT: PRODUCTION OF HEAT; LOSS OF HEAT. 

 DISTRIBUTION OF HEAT; REGULATION OF HEAT. 



HAVING described the mechanism by means of which the 

 lungs rid the body of carbonic acid and water, and of how the kid- 

 neys relieve it of urea, salts, and water, it now remains for us to 

 explain how the skin plays its part in elimination by yielding 

 up water, and a certain amount of carbonic acid and salts. 



The skin. The skin is not, like the kidneys, set apart to per- 



- sw 



M 



FIG. 110. SECTION OF EPIDERMIS. (Ranvier). H, horny layer, consisting of 

 s, superficial horny scales; sic, swollen-out horny cells; s.l. clear layer; M, Malpig- 

 hian layer, consisting of s.gr. granulur layer; p, many-sided or prickle cells; c, 

 columnar cells. Nerve fihrils may be traced passing up between the epithelium cells 

 of the Malpighian layer. 



189 



