1916] FOODS HUMAN NUTRITION. 269 



amino acids, such as tryptophane, lysin, or cystin, the authors state that an 

 essential feature of the construction of new tissue is a synthesis of new protein. 

 Growth will, therefore, be limited by any factor preventing this synthesis, such 

 as the lack of any component amino acid which can not be manufactured 

 directly in suitable amounts by the body. The authors review briefly earlier 

 experiments by themselves and others, which show the effects of tryptophane, 

 lysin. and cystin upon growth when added to an otherwise dolicient ration. 



Additional experiments with laboratory animals (rats) are reported which 

 show that " the need for tryptophane and lysin is governetl by the ' law of 

 minimum,' the rate of growth increasing with increasing amounts of these 

 amino acids furnished by the food until the normal rate is attained. When 

 larger quantities of these amino acids are supplied growth is not made more 

 rapidly, for the construction of new tissue is no longer limited by deficiencies 

 in the requisite supply of any element of the food, but by the natural capacity 

 of the animal to grow." 



The energy content of the diet (Set. Mo., 2 {1916), No. 3, pp. 279-306) .—The 

 following four papers form a symposium and were read before the Section of 

 Physiology and Experimental Medicine of the American Association for the 

 Advancement of Science, at Columbus, Ohio, in December, 1915 : 



Proteins in groicth, by Ruth Wheeler (pp. 279-282). — This paper summarizes 

 the results of recent investigations relative to the role of amino acids in nutri- 

 tion and emphasizes the importance of the amino acid content, as well as 

 other characteristics of proteins, in determining their food value. 



The mineral nutrients in practical human dietetics, by E. B. For')os (pp. 

 282-289). — In this article the author enumerates the functions of lae mineral 

 elements in metabolism and discusses their importance in the dui. The bulk 

 of the material is essentially the same as that noted in an earlier paper (E. S. 

 R., 35, p. 62). 



The chemical nature and physiological significance of so-cullcd vitamins, by 

 C. Voegtlin (pp. 289-293). — Recent investigations by the author and others are 

 summarized and the importance of vitamins in practical dietetics is considered. 

 A table is given showing the common foods which are relatively rich and rela- 

 tively poor in antineuritic and antiscorbutic properties. 



Food selection for rational and economical living, by C. F. Langworthy <» (pp. 

 294-306).— The author considers at length a number of factors which should be 

 taken into account in securing an adequate and economical diet which at the 

 same time gives satisfaction. Information is given regarding the selection, 

 preparation, and cooking of foods, and the planning of meals. 



As a guide for the housekeeper in the wise selection of food materials for a 

 meal or for a day's ration, and also as a means of checking up and criticizing 

 meals served, the author classifies the common foods into five groups, corre- 

 sponding to their distinctive functions in nutrition. " The groups may be de- 

 scribed in terms of the dietitian as follows: (1) Foods in which protein bears a 

 higher proportion to fuel value than it does in the well-chosen diet as a whole ; 

 (2) those in which fuel value is high in proportion to protein, owing chiefly to 

 the presence of much starch; (3) those in which fuel value is high, owing to 

 the large percentage of fat ; (4) those whose chief value is mineral constituents 

 and vegetable acids (the latter important from the standpoint of flavor as well 

 as of body needs) ; and (5) those which (like the foods in Groups 2 and 3) 

 have a high fuel value, but in this case due to the presence of sugar. From the 

 standpoint of fuel value only, it is obvious that Groups 2 and 5 could be com- 

 bined. From the standpoint of the well-chosen and palatable meal, on the other 



« Sci. Amer. Sup., 81 (1916), Nos. 2100, pp. 210, 211 ; 2101, pp. 230, 231. 

 54530°— No. 3—16 6 



