a similar growth response was obtained when the b12 plus hypoxanthine was replaced by 4 micrograms of hypoxanthine/ml in combination with 100 ng of thymidine/ml , 1 microgram of folic acid/ml or 1 microgram of folinic acid/ml , even though 1 microgram of folic acid/ml already was present in the medium .
C0023413
folinic acid
C0016410
folic acid