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CHAPTER IV 

 THE PROTEIN METABOLISM OF MANKIND 



HAVING surveyed in general terms some of the food materials 

 extensively used in different countries, and having examined 

 their gross chemical composition and the averages of the per- 

 centage absorption of their proximate principles, we shall now 

 take into consideration the dietaries of mankind in general, and 

 discuss the nutritive requirements and the extent of nitrogenous 

 interchange attained by the various peoples concerning whom 

 information is available. 



In his introductory remarks on the general principles of 

 dietetics Sir Lauder Brunton states : " The subject of food is 

 one upon which countless experiments have been made by 

 myriads of men during thousands and perhaps millions of years. 

 In all parts of the world, from prehistoric times until now, men 

 have been constantly engaged in finding out what things were good 

 to eat and what things they had better avoid." It is only, how- 

 ever, within comparatively recent times that the study of dietetics 

 has been accurately pursued and placed on a scientific footing. 

 Students of nutrition from different parts of the world have laid 

 their contributions at the feet of Knowledge, and Wisdom and 

 Understanding are gradually emerging from darkness into light. 



Japan, Russia, and the different European countries, have all 

 made valuable additions in the advances recorded, but, at the 

 present time, to none do we owe the same debt as to America 

 for the stimulating influence of her many workers in this field, 

 and for the exceedingly valuable contributions they have made 

 to the scientific pursuit of the principles of proper feeding. 



In the following pages it will be found necessary to make 

 reference to many of those engaged in this line of research, as, 

 for instance, Atwater, Langworthy, Benedict, Folin, etc., in 

 America ; Zuntz, Ranke, Pfliiger, v. Noorden, and others, in 

 Germany ; but it is only meet that special mention should be 



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