THE HYGIENE OF NUTRITION 225 



venient waste-product in the human body. Individual 

 susceptibility to the action of caffein varies greatly. 

 Where one person notices little or no reaction after a cup of 

 coffee, another is exhilarated to a marked degree and hours 

 later may find himself lying sleepless with tense or trem- 

 bling muscles, a dry, burning skin, and a mind feverishly 

 active. Often it is found that a more protracted disturb- 

 ance follows the taking of coffee with cream than is caused 

 by black coffee. 



It is too much to claim that the use of tea and coffee is 

 altogether to be condemned. Many people, nevertheless, 

 are better without them. For all who find themselves 

 strongly stimulated it is the part of wisdom to limit the 

 employment of these decoctions to real emergencies when 

 uncommon demands are made upon the endurance and 

 when for a time hygienic considerations have to be ig- 

 nored. If young people will postpone the formation of the 

 habit they will have one more resource when the pressure 

 of mature life becomes severe. 



Chocolate and its derivative, cocoa, may be regarded as 

 having somewhat similar properties. There is a measure 

 of drug action, though it is less pronounced than in the 

 case of coffee. Here the active principle is theobromin, 

 nearly related to caffein. Chocolate is more than a food 

 accessory, being exceedingly nutritious. A chocolate 

 habit is easily formed, but, aside from threatening damage 

 to the teeth, it is comparatively innocent. 



Mineral Salts. These compounds have been referred 

 to in an earlier chapter as forming an essential part of the 

 tissues. Hence they must be supplied in sufficient quan- 

 tity and variety during the period of growth. There is no 

 real danger of failing to do this, though there are certain 

 cases of malnutrition in which the central difficulty seems 

 to be the lack of such constituents in the body of the 

 child. The actual trouble is probably with the absorp- 

 tion- rather than with the diet. Thus, in rickets there 

 is an evident deficiency in the quantity of lime-salts in- 

 corporated into the developing skeleton, but it is not 



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