METABOLISM AND GROWTH FROM BIRTH TO 



PUBERTY. 



INTRODUCTION. 



In the past decade the trend of thought in the physiology of growth 

 has been towards a chemical analysis of the several growth factors. 

 The embryonic animal (which with mammals receives nourishment 

 from its mother through the placenta, and with other animals from 

 the previously deposited food material in the egg) grows in accordance 

 with the nutrients supplied. After birth various types of foods are 

 brought to it by the mother or by other agencies. The selection of 

 the diet best fitted, both in amount and in quality, to acquire growth 

 has received a great deal of experimental attention. The importance 

 of the mineral constituents and the nature of the proteins used in the 

 construction of new tissue have been emphasized; particularly, the 

 so-called " unidentified food accessory substances," which make for 

 growth, have been exhaustively studied by Hopkins, 1 Osborne and 

 Mendel, 2 and McCollum. 3 As a result of these extensive investigations 

 of the subject, it is clear that a large number of factors, heretofore 

 almost neglected in research, are absolutely essential for the proper 

 growth of the immature animal. 



With a study of these essentials there has proceeded, although 

 perhaps with less intensity, a study of certain physiological constants 

 characteristic of the immature animal, particularly of the human 

 animal. While the anthropologists have given us extensive measure- 

 ments of the growth in that period of development in which growth 

 is most marked, i. e., in the earlier years of life, relatively little is 

 known regarding the fundamental basal metabolism during this period. 

 The Nutrition Laboratory, in the belief that a careful survey should 

 be made of the metabolism of all mankind from birth to old age, has 

 been occupied for nearly a decade in the charting of this little-known 

 field of human basal metabolism. The writers' special province has 

 been that of infants and children. As an indication of the extent and 

 thoroughness of the original program in its several subdivisions, we 

 may call attention to our report of a research on the physiology of the 

 new-born infant, in which over 100 new-born infants were studied, 



1 Hopkins, Journ. Physiol., 1912, 44, p. 425. 



2 Osborne and Mendel, Carnegie Inst. Wash. Pub. No. 156, 1911. 



3 McCollum, The newer knowledge of nutrition. New York, 1918. 



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