364 THE HUMAN MACHINE 



perfectly clean. Oily skin needs only mild soap and 

 water, but dry skin can be improved by the use of a good 

 cleansing cream (preferably one containing a little lanolin 

 or other animal fat) after washing. 



There is no such thing as a "skin food" beyond what 

 is taken into the mouth as food for the whole body. 

 Remember a healthy skin is a natural skin. 



The Skin Regulates Our Body Temperature. We are all 

 aware of the fact that sometimes we feel hot or feel cold, 

 but if we were to take the body temperature at either of 

 these times, we would find it varied little from its normal 

 heat of 98.6. To be sure, the outer part of the skin 

 would be colder on a cold day and warmer on a warm 

 day, but the skin itself has a very complex mechanism 

 for regulating our body temperature. By means of the 

 sweat glands shown in the diagram on page 360 as little 

 coiled tubes, and the very delicate nervous apparatus 

 which controls the amount of sweat released, the skin is 

 enabled to regulate the heat of the body. When we do 

 more work and the body becomes warmer from the in- 

 creased oxidation within it, the skin automatically is 

 enabled to throw off this heat and it is able also to retain 

 more heat on a cold day. 



How the Body Loses Heat. Heat is lost from the body 

 by the three methods we have studied in the preceding 

 chapters. A certain amount of heat is lost by conduction, 

 although the air is a very poor conductor, and warm 

 fabrics get much of their heat-holding qualities because 

 of the stagnant air confined in their meshes. Most of our 

 heat from the body is lost by convection. When we fan 

 ourselves, we create a current of air, causing cooler air 

 to replace the warm air about the body. We also lose 

 heat by radiation to other solid objects which are cold. 

 It is very easy to take cold by sitting on the damp ground, 

 or close to cold windows or walls, because in this way 



