“I may take some of these samples to study myself?” interrupted Kennedy, as though the story of vitamines was an old one to him.

“By all means,” agreed Leslie.

Craig selected what he wanted, keeping each separate and marked, and excused himself, saying that he had some investigations of his own that he wished to make and would let Leslie know the result as soon as he discovered anything.

Kennedy did not go back directly to the laboratory, however.  Instead, he went up-town and, to my surprise, stopped at one of the large breweries.  What it was that he was after I could not imagine, but, after a conference with the manager, he obtained several quarts of brewer’s yeast, which he had sent directly down to the laboratory.

Impatient though I was at this seeming neglect of the principal figures in the case, I knew, nevertheless, that Kennedy had already schemed out his campaign and that whatever it was he had in mind was of first importance.

Back at last in his own laboratory, Craig set to work on the brewer’s yeast, deriving something from it by the plentiful use of a liquid labeled “Lloyd’s reagent,” a solution of hydrous aluminum silicate.

After working for some time, I saw that he had obtained a solid which he pressed into the form of little whitish tablets.  He had by no means finished, but, noticing my impatience, he placed the three or four tablets in a little box and handed them to me.

“You might take these over to Leslie in the department laboratory, Walter,” he directed.  “Tell him to feed them to that wabbly-looking pigeon over there—­and let me know the moment he observes any effect.”

Glad of the chance to occupy myself, I hastened on the errand, and even presided over the first feeding of the bird.

When I returned I found that Kennedy had finished his work with the brewer’s yeast and was now devoting himself to the study of the various samples of food which he had obtained from Leslie.

He was just finishing a test of the baking-powder when I entered, and his face showed plainly that he was puzzled by something that he had discovered.

“What is it?” I asked.  “Have you found out anything?”

“This seems to be almost plain sodium carbonate,” he replied, mechanically.

“And that indicates?” I prompted.

“Perhaps nothing, in itself,” he went on, less abstractedly.  “But the use of sodium carbonate and other things which I have discovered in other samples disengages carbon dioxide at the temperature of baking and cooking.  If you’ll look in that public-health report on my desk you’ll see how the latest investigations have shown that bicarbonate of soda and a whole list of other things which liberate carbon dioxide destroy the vitamines Leslie was talking about.  In other words, taken altogether I should almost say there was evidence that a concerted effort was being made to affect the food—­a result analogous to that of using polished rice as a staple diet—­and producing beriberi, or, perhaps more accurately, polyneuritis.  I can be sure of nothing yet, but—­it’s worth following up.”