THE STORY OF THE LUNGS, SKIN AND KIDNEYS 93 



however, from any circumstances the nervous 

 control is lessened, the bloodvessels dilate or expand, 

 with the result that a greater flow of blood passes 

 through them and greater activity of the sweat 

 glands is produced. A warm bath produces this 

 effect. It relaxes the skin and bloodvessels, brings 

 more blood to the skin surface, and this favours 

 perspiration. Cold acts in a reverse fashion and 

 diminishes the supply of blood, lessening at the same 

 time the amount of perspiration given off. Some- 

 thing of this skin regulation of temperature and the 

 resulting alteration produced in its work may be 

 appreciated in the difference between the work of 

 the kidneys and skin in summer and in winter. In 

 summer when the skin acts freely, the work of 

 the kidneys is lessened, whereas in cold weather skin- 

 action is apt to be in some degree checked and the 

 kidneys excrete more fully. It is the evaporation of 

 perspiration from the skin surface that aids largely 

 in the regulation of temperature. The sweat, as a 

 fluid, evaporates and passes off into the air, and thus 

 removes a certain amount of heat from the body 

 with the result of cooling the body at large. On the 

 other hand, when the atmosphere is cold, less sweat 

 being produced, the loss of heat from the body is 

 lessened; and so under the varying circumstances 

 of life and under varying degrees of temperature 

 the bodily heat is regulated and maintained at very 

 much the same degree 98.4 degrees F. 



THE CARE OF THE SKIN. Of the most extreme 

 importance to health is the care of the skin. Recog- 

 nising the elaborate functions it performs, we are 

 taught our duty to the skin in maintaining its cleanli- 

 ness and in encouraging its work. Interference with 

 the functions of the skin may be productive of very 



