July 21, 1921] 



NATURE 



667 



cent, of edestin. Fig. 3 shows that the same amount 

 of growth resulted in the same time with these quanti- 

 ties of proteins. 



Suitable mixtures of proteins have also been tested, 

 and attempts are being made to find out the most 

 convenient addenda for making the proteins of cereals 

 more adequate for the growth of animals, i.e. adding 

 what we may call "good" protein to "bad" protein 

 to make the latter efficient as food. Leaf and seed 

 proteins are good as a mixture. Fig. 4 shows that if 

 zein i be supplemented with lactalbumin |, normal 

 growth results. 



Fig. 3. — After Osborne and Mendel. 



Economically, it may be better to use an expensive 

 protein as food for animals and produce rapid growth 

 than to feed for longer periods on poor proteins and 

 get slower growth. A simple calculation brings out the 

 problem to be solved. We may wish to build up the 

 casein of milk with 16 per cent, of glutamic acid, and 

 we are provided with wheat gliadin with more than 

 40 per cent, of this unit. There is waste of glutamic 

 acid. Gliadin further contains 02 per cent, of lysine, 

 whilst casein contains 6 per cent. To produce this 



Fig. 4. — After Osborne and Mendel. 



amount we require thirty times as much gliadin, and, 

 consequently, the waste of glutamic acid is further 

 increased. 



Cannibalism is the most economical method of pro- 

 tein nutrition, as the amino-acids of the food are in 

 the exact proportion required by the tissues. The 

 nearest parallel to this is the nursing of the young 

 animal bv its mother ; the child actually gets the 

 proteins of the mammary glands. 



Recent work shows that quality of protein is most 

 probably the primary cause of the disease pellagra, 

 although there are some indications that general in- I 

 NO. 2699, VOL. 107] 



sufficiency of protein together with improper salt 

 supply are contributory factors. 



Pellagra is a peculiar disease characterised by severe 

 disturbance of the whole digestive tract, by skia 

 lesions, usually bilaterally symmetrical, and oftea 

 mistaken at first for sunburn or chapping of the 

 hands, face, neck, and other exposed areas. The 

 nervous system is also affected. There is no definite 

 record of pellagra in Europe before maize was intro- 

 duced into Spain by Columbus. From Spain the 

 disease spread to France, Lombardy, and eastwards^ 

 wherever maize was extensively used for food in the 

 poorer agricultural districts. The relation of maize 

 to the disease puzzled the me<lical profession for 

 nearly two hundred years, for the disease alsa 

 occurred where maize was not used, while in some 

 districts maize was used but there was no pellagra.. 

 Roussel in 1866 showed that it could be cured by 

 good food, and Lorentz (1914) and Willets (1915) suc- 

 cessfully treated advanced cases with a generous diet. 

 Goldberger also cured and prevented the seasonal 

 appearance of pellagra in lunatic asylums and 

 orphanages by increasing the quantity of meat and 

 milk ; previously the diet had been deficient in these 

 respects. Goldberger, by the offer of a free pardoa 

 from the Governor of Mississippi, was enabled to. 

 obtain eleven convicts as volunteers for a feeding ex- 

 f>eriment to determine if pellagra could be produced 

 by an unbalanced diet in healthy white men. The- 

 "pellagra squad," as they were called, were fed oa 

 white wheat flour, various maize preparations ^ 

 polished rice, sugar, sweet potatoes, pork fat, cab- 

 bage, and turnip-tops. The food had an energy value 

 of 2950 Calories, and was amply sufficient in this 

 respect, but after the second month on this diet the 

 men complained of weakness, headache, abdominat 

 pain, and other minor discomforts. After five months 

 six of them developed a rash which was pronounced] 

 by experts to be identical with that seen in pellagra, 

 and during the last four weeks all the prisoners had 

 shown marked loss of weight and were much out of 

 health. Pellagra would probably have developed in 

 the remainder, but the experiment had to be aban- 

 doned owing to the refusal of the men to continue. 

 A control was carried out at the same time ; their 

 diet contained some meat, eggs, and buttermilk ; 

 there was not a single case of pellagra and no pro- 

 gressive loss of body-weight. 



These and other facts clearly point to the diet as 

 the controlling factor in the cause and prevention of 

 the disease. The determining factor seems to be the 

 quality of the protein. Good evidence on this point 

 has been furnished by Wilson, of Cairo. In 1916 

 pellagra broke out in a camp for Armenian refugees 

 at Port Said. Wilson showed that the diet at first 

 supplied was inadequate both in energv supply (2200 

 Calories) and in protein supply ; indeed, 92 per cent, 

 of the protein was of vegetable origin — three-quarters 

 from wheat and one-quarter from maize. 



By determining the least daily amount of a protein 

 required to keep a man from loss of body protein, 

 Thomas was able to assign a series of values to pro- 

 teins representing their biological efficiency. The 

 comparative values according to the quantitv required 

 to maintain a man w'ithout loss of nitrogen and bodv-^ 

 weight were : 



88 

 • 79 



40 

 30 



The biological value of meat is therefore three 

 times that of maize. Wilson calculated that the diet 

 as given to the refugees was equal to 22 gm. of 



