THE NATIONAL GEOGRAPHIC MAGAZINE 



357 



ONE OF DR. MC COUAJM'S RATS, RAISED ON A PERFECTLY SATISFACTORY DIET 



Note the brightness of its eyes, the smoothness of its ears, and the general appearance of 

 sleekness of its hairy coat. This is one of the 1,500 rats which compose the laboratory of 

 Dr. E. V. McCollum at the School of Hygiene and Public Health of Johns Hopkins Uni- 

 versity, where the dietary values of our common foods are being studied and where in par- 

 ticular the biological value of the different proteins which we eat is tested as to its fitness 

 to be employed by our bodies in the building up of our body cells. It is through the researches 

 of Dr. McCollum that the role of the unidentified dietary essentials, "fat soluble A" and 

 "water soluble B," has been worked out. 



lions of Americans giants and dwarfs, fat 

 ladies and living skeletons, but far more 

 inspiring and educational would be the 

 exhibition of some of those fine physical 

 specimens of humanity from southern 

 Italy who have lived for generations with- 

 out eggs, without milk or cheese, and with 

 meat only a few times a year. These 

 Italian peasants, according to Lusk, have 

 built up these strong working bodies on 

 the simple diet of corn-meal, beans, olive 

 oil, and the leaves of the cabbage and the 

 beet, with garlic and Spanish peppers for 

 flavoring. 



It is these Italian peasants who for 

 years have done the heavy construction 

 work of our railroads, getting rich be- 

 cause they are willing to live on their 

 cheap foods, while side by side with them 

 work the Southern darkies, who have de- 

 manded meat twice a day and paid any 

 price for it. 



McCollum has shown through his rat 

 experiments that the matter is not so 

 mysterious as it was thought to be. The 

 secret lay in the use of green vegetables. 

 Rats will starve and men, too, on Indian 

 corn alone. They will do better, although 

 not really well, on corn and olive oil ; but 

 on corn and oil, with the addition of 

 greens of some kind, they thrive and re- 

 produce. 



TWO NEWL,Y DISCOVERED FOOD ESSENTIALS 



The human machine is, after all, a sim- 

 ple one in many ways and can take its 

 fuel (energy-yielding food) as well from 

 cheap as from expensive foods, but it 

 must have all of the different kinds or it 

 runs down quickly. Starches, fats, pro- 

 teins, minerals, and water are the five 

 great food groups for which we are ac- 

 customed to planning in our diets ; but 

 until recently we have not known about 



