362 THE HUMAN MACHINE 



Sticky or waxy fixatives should be avoided because they 

 may harden into a thin coating all over the scalp, which 

 stunts the growth of the hair. 



Hair should be shampooed as often as it needs it. The 

 average time is once every two weeks. Pure Castile soap 

 is the best for shampooing. All strongly alkaline sub- 

 stances, like laundry soap or washing powders, should be 

 avoided. Where the water is hard, it can be softened 

 with a little borax or soda, dissolved in the water before 

 soap is used. The scum that often forms on the hair 

 when it is washed in hard water can be removed by care- 

 ful rinsing with a little lemon juice or vinegar (also to be 

 added to the water, never poured directly on the hair). 

 Both water softeners and acid rinses must be used spar- 

 ingly, because they make the hair reddish, harsh, dry, 

 and brittle. Hair that is burned or dried from the sun, 

 salt-water bathing, or any other cause can be improved 

 by treatments with a mixture of olive and castor oils. 



Care of the Nails. The nails on the fingers and toes, 

 like the hair, and like the feathers, scales, horns, and 

 hoofs on lower animals, are outgrowths from the inner 

 skin. Normally they grow continuously, and if one falls 

 out or is injured, another comes to take its place. Young 

 people should learn to care for their nails as carefully as 

 they wash their hands. The skin at the base should be 

 pushed back regularly, and the nails should be kept clean 

 under their free edge by means of a blunt, soft stick. 

 Metal instruments may injure or disfigure the nails. 

 They should be well shaped with a thin file, and, above 

 all, should never be bitten off, because biting causes 

 changes in form and growth which can never be corrected 

 throughout life. Many a man and woman have regretted 

 in later years the bad habit of biting the nails in childhood. 



Care of the Skin. No other part of the human machine 

 needs care more than the skin. In the first place it should 



