NUTRITION. 373 



NUTRITION. 



Osborne, T. B., and L. B. Mendel, New Haven, Connecticut. Continuation 

 and extension of work on vegetable proteins. (For previous reports see 

 Year Books Nos. 3-20.) 



Students of the vitamine problem seem at present to be in accord in the 

 belief that the now-recognized food accessories are not synthesized de novo by 

 the higher animals, but are derived from their food-supply. Furthermore, the 

 comparatively rapid onset of symptoms of disorder following the lack of vita- 

 mine B in the diet leads to the conclusion that normal animals do not possess 

 any large available reserve of this food factor. It is of obvious importance, 

 therefore, to secure a quantitative estimate of the actual amounts of the 

 different vitamines requisite for the proper physiologic function of the various 

 animal organisms at all stages of their existence and under the different con- 

 ditions represented by unhke age, sex, activity, diet, planes of metabolism, or 

 other possible modifying circumstances. Pubhshed statements have awak- 

 ened a widespread belief that vitamine B is essential primarily for growth. 

 The evidence, however, is not very cogent, particularly in view of the admitted 

 fact that the common experimental animals of all ages inevitably decline when 

 vitamine B is omitted from their diet. 



In our report for last year we stated that an extensive series of feeding trials 

 was in progress in which the only variable, aside from the variations in the 

 voluntary daily food intake, has been the amount of vitamine B fed daily, 

 apart from the rest of the ration, as tablets containing dried brewery yeast. 

 These tests continued over a period of one year for each animal, the beginning 

 of such a dietary regime being made at different ages (and consequently 

 different sizes) with animals previously maintained on the mixed diet custom- 

 arily furnished after weaning to our stock colony. In this way the doses of 

 this yeast required at different ages until adult size was reached could be 

 ascertained; also whether a more or less prolonged preHminary period of less 

 "artificial" feeding on food mixtures which have been demonstrated to be 

 adequate in every respect for the nutritive well-being of the rat would alter 

 the subsequent vitamine requirement. Thus, the feeding trials in successive 

 groups on the same yeast dosage were begun when the animals had reached 

 approximately 40, 70, 150, and 240 grams respectively of body-weight. The 

 results of these experiments are nearly ready for publication. 



Obviously, when the daily intake of yeast remains unchanged while the 

 animal is growing, the dosage of vitamine estimated on the basis of body- 

 weight, stature, or surface area becomes progressively altered. An estimate 

 of the actual dosage in our numerous experiments under strictly comparable 

 conditions in terms of 100 grams body-weight is admittedly open to theoretical 

 objections, just as are the various units which have been proposed for the 

 record of basal metabohsm. 



Broadly speaking, it appears as if the vitamine B requirement in the case of 

 the rat under conditions of growth or maintenance upon a food of constant 

 quahtative and quantitative make-up bears a fairly definite quantitative 

 relationship to the mass of active tissue. Under the conditions of our 

 experiment the daily requisite per hundred grams of rat approximates what is 

 contained in 50 to 60 milHgrams of our dry yeast. This conclusion is reached 



