19171 POODS HUMAN NUTRITION. 265 



simple combinations of leaf and seed were fed as monotonous diets. It has 

 been found that with wheat, oats, and maize in equal proportions both salts 

 and fat-soluble A must be added to the ration before growth can take place, 

 and that " it is difficult if not impossible to obtain even a moderate amount 

 of growth over an extended period on a diet restricted to the seeds of plants." 



Satisfactory protein mixtures can be had from seed mixtures, and experi- 

 ments have shown also that certain seeds, such as flaxseed and millet, con- 

 tain the fat-soluble A in fairly liberal amounts. " Since the water-soluble B 

 is everywhere abundant in the seeds the cause of failure to secure growth on 

 seed mixtures is seen to lie in the amount and character of the inorganic 

 moiety. ... Of the seven most important seeds from the standpoint of human 

 uutritiou and animal production only cotton seed and flaxseed contain a high 

 total inorganic content, and in both cases the ash is very poor in three important 

 elements, sodium, calcium, and chlorin. Since a pronounced deficiency of 

 these elements is characteristic of all other seeds as well, no combinations of 

 seeds will supply these elements in satisfactory amounts." 



The necessary inorganic supplements may be secured in some localities 

 through the drinking water, which would enable the animals in those locali- 

 ties to grow on a ration restricted to seeds. 



" The leaf is distinctly different from the seed in its dietary properties in 

 two respects : Its total inorganic content is very high, and it is especially rich 

 in both sodium and calcium, both of which are deficient in the seeds generally. 

 In addition the leaf of the plant is several times richer In fat-soluble A than 

 are the wheat, oat, and maize kernels. Certain seeds approximate the value 

 of the leaf in this substance. Hempseed is distinctly better than those just 

 named, but flaxseed and millet seed are still richer than hempseed and may 

 readily be incorporated in the diet in amount sufficient to meet the needs of 

 an animal for the fat-soluble A during growth." 



Feeding' experiments with deficiencies in the amino-acid supply: Arginin 

 and histidin as possible precursors of purins, H. Ackeoyd and F. G. Hopkitsis 

 {Biochem. Jour., 10 (.1916), No. ^, pp. 551-576, figs. 6). — This paper reports 

 the results of a large number of experiments with laboratory animals (rats). 

 The data obtained may be summarized briefly as follows : 



Removal of arginin and histidin from the diet of rats which had been 

 previously growing on a complete amino-acid mixture resulted in a rapid loss 

 of body weight. Restoration of the missing diamino acids to the diet resulted 

 in renewing growth. 



Restoration of arginin alone or histidin alone resulted in no loss of weight 

 and in some cases in growth. Nutritional equilibrium was possible in the ab- 

 sence of one of these related protein constituents, although not in the absence 

 of both. A reason suggested for this is that each one of them can in metabolism 

 be converted into the other. When arginin and histidin were both removed 

 from the food the amount of allantoin in the urine was much decreased, but 

 when they were replaced the excretion returned to normal. The decrease was 

 very much less when either one of these diamino acids was present alone. 



When tryptophan was removed from the food no decrease of allantoin oc- 

 curred, although nutritional failure was even greater than when arginin and 

 histidin were withheld. No decrease of allantoin excretion was observed when 

 the animals were losing weight as the result of the absence of vitamins from 

 the diet. 



In view of tliese results the authors suggest that arginin and histidin play 

 a special part in purin metabolism, probably constituting the most readily 

 available raw material for the synthe.sis of the purin ring in the animal body. 



