fractions may themselves be poisonous or otherwise unsuited for mixture in
a diet. It is obvious therefore that interest is keen in any possibility
of devising a test that will be specific, quick and not require
modification of the material tested, because of its unsuitability for
feeding. In 1919 Roger J. Williams proposed a method that seemed to offer
promise in these respects but which is not yet in the form for
quantitative use. It offers promise that entitles it to a special chapter
for discussion and the next chapter presents the present status of the so-
called yeast test for vitamine "B."

Before turning to this test it is well to call attention here to the
importance of the experimental animal. Without the polyneuritic fowls we
might never have cured beri-beri, the guinea pig made the solution of the
scurvy problem possible and if some way of inducing pellagra in an animal
can be devised that scourge may yet be eliminated.



CHAPTER IV


THE YEAST TEST FOR VITAMINE "B"

As far back as the days of Pasteur a controversy arose over the power of
yeast cells to grow on a synthetic medium composed solely of known
constituents. This controversy hinged on a discussion as to whether these
media were efficient unless reinforced with something derived from a
living organism. In 1901 Wildier in France published an article in which
he showed that extracts of organic matter when added to synthetic media
had the power to markedly stimulate the growth of yeast organisms. He did