ne of us produced conclusive evidence that a calf will grow normalIy
to maturity and produce normal offspring-on a ration that
carries an insufficient amount of the vitamin B compIex to support
growth and weI1 being in rats (1). In later investigations we
determined that vitamin B in milk is not dependent on the
presence of this vitamin in the ration of the cow (2). Three cows
that were fed for over 2 years, throughout their growth period, on
a ration that was decidedly deficient in vitamin 13, were used in
this study. The evidence obtained in these investigations appeared
to indicate that cattle, and possibly all other ruminants,
possess the ability to synthesize vitamin B. Damon (3), Kuroya
and Hosoya (4), HelIer et al. (5), Scheunert and Schieblich (S),
Sunderlin and Werkman (7), and others have made contributions
to our knowledge of the possible synthesis of vitamin B complex
by bacteria. The present paper is intended to set forth the
results of an investigation which was designed to determine
whether the microorganisms present in the rumen of one of our