376 CARNEGIE INSTITUTION OF WASHINGTON. 



rat. In this way comparatively small types of adults might arise. To 

 answer this question we have undertaken new experiments in which the ani- 

 mals have been dwarfed at a comparatively early age for considerable periods 

 through chemically inadequate diets and are now being permitted to grow 

 through a change to a liberal mixed diet. We shall soon be in a position to 

 determine to what extent, if at all, the stunting in earlier years may have 

 altered the ultimate capacity to attain adult stature. 



In preparation for the foregoing tests, we have repeated some of our earlier 

 investigations in suppression of growth through the use of the protein gliadin 

 which is relatively deficient in the indispensable amino-acid lysine. So far 

 as it concerns the inability to grow despite an otherwise adequate diet, the 

 outcome has corroborated our earliest observations. Professor H. H. Donald- 

 son, of the Wistar Institute, has made measurements of a number of animals 

 which have been kept without exceeding a weight of approximately 100 

 grams over periods of 100 and 200 days respectively. His findings will afford 

 comparisons of the development of the different organs and skeleton under 

 conditions of prolonged suppression of growth. It is worthy of note that 

 some of these stunted animals on the gliadin diets were at first intentionally 

 maintained for some time on food devoid of vitamine A, whereupon they 

 developed the characteristic ophthalmia and were in turn completely cured, 

 although without growth, by the administration of cod-liver oil; despite these 

 periods of undoubted ill health, the ultimate capacity to grow has been main- 

 tained. Even during maintenance without growth at relatively early ages, 

 the pathological manifestations of deficiency of vitamine A exhibit them- 

 selves. This is contrary to our former belief that the pathological effects of 

 lack of vitamine A failed to manifest themselves so long as no growth took 

 place. 



In view of the fact that gliadin yields a measurable, although extremely 

 small, quantity of lysine, it might be supposed that, provided sufficient of the 

 protein could be utilized, growth could occur even on gliadin. In experi- 

 ments in which this protein constituted 80 per cent of the entire otherwise 

 appropriate food we have found that this is the case. Rats fed on this mix- 

 ture from the age of 30 to 40 days doubled their weight within 45 days. 



The question of the vitamine-content of milk has, very properly, attained 

 considerable prominence, not only in its scientific aspects in relation to 

 nutrition, but also from the standpoint of public health. Experiments under- 

 taken by us at various times have indicated the necessity of feeding as much 

 as 16 c. c. of fresh cow's milk per day as the sole source of vitamine B to secure 

 growth at a normal rate. These results have been substantiated by several 

 investigators; and although there appears to be a variation in some cases in 

 the vitamine B content of milk, depending on the character of the diet of 

 the cows, the results have, with the exception of Hopkins's experiments, been 

 in harmony with our own in showing that even under the most favorable 

 circumstances it requires additions of more than 10 c. c. of milk per day to 

 effect a food intake adequate for the growth of rats at a normal rate. The 

 successful results obtained by Hopkins with as little as 2 c. c. of milk per day, 

 fed in the same way, have stimulated us to renewed tests in which the feedings 

 were begun, as in most of Hopkins's experiments, when the rats were still 

 quite young, often weighing not more than 40 grams. These new experi- 



