Early in the last century, long before a science of nutrition had been founded, the importance of protein in the diet was recognized. But so also was the recognition that protein is the most expensive part of the dietary. Meat, which is largely protein, became a luxury beyond the reach of the poor during the stirring days of the French Revolution and the years that followed. What was to be done? The people had to have meat because it contained protein, but perchance there were substances other than meat that contained this precious nutrient? Others were known, such as the casein in milk and the albumen in egg, but eggs and milk were, if anything, even more expensive than meat.

Then a happy idea struck the scientists of the French Academy. Were there not enormous quantities of bones discarded yearly out of which gelatin could be extracted, and was not this gelatin a protein? Behold the panacea! D'Arcet invented an economical method for extracting the gelatin, and a committee of the Academy of Medicine, in solemn session assembled, declared the process and the food all that could be desired.

The learned Academy's report was published in 1814. On the strength of this report the French Government began their experiments at the hos-pitals. Why sick people rather than criminals were selected is not clear. To-day when the United States Department of Public Health desires to experiment with people, it usually turns to Sing Sing and places of that kind; and then the experiment is conducted with volunteers only.

The sick people in some of the French hospitals were given gelatin in place of other proteins. They digested it easily enough; gelatin jellies in fact are easily digestible. But after a time the sick people fell sicker, - in such numbers and under such conditions that only the change of diet could account for it Like the politician who is the hero to-day and becomes the traitor to-morrow, poor gelatin was thrust from its lofty pedestal back into the refuse from which it had been rescued.

But what was the matter with gelatin? Why could not this protein substitute the proteins in meat, egg and milk? Years elapsed before a satisfactory answer was found. At any rate, the world in the meantime learnt the lesson that merely giving a man 100 grams of protein without specifying the kind of protein meant no more than giving a man food yielding a sufficient number of calories, without, however, specifying how the food was to be distributed among the classes of foodstuffs. But life on this earth continued, and many died and many more were born, because instinct and experience led us to do the things we did do. To find an answer to the question why one protein is less nutritive than another requires an examination of the fate of the protein after it has entered the system. But here the earlier investigators suffered from the drawback that they were ignorant of the chemical constitution of proteins, and were therefore ill-equipped to study the changes of the protein in the system.