Abstract
Vitamin B_<12> assay in blood was investigated. It was observed that the following method is most appreciable for many subjects and a long term experiment. Microbiological assay with L. leichmannii in using Nissan media for a stock culture, an inoculum culture and an assay medium are suitable for the purpose of the present experiment. KCN boiling method by Hayashi et. al. is suitable for the extraction of vitamin B_<12> from the whole blood. The alkali stable factor in the whole blood of our samples was negligible. Samples of whole blood can be kept at least for 10 days without changing its vitamin B_<12> content under a frozen state. The preparations of vitamin B_<12> extracted from the whole blood can be stored under toluene at 4℃ for a week, Variations of daily vitamin B_<12> value in whole blood of one subject were less than 20%.
