Microbiological Assay of Vitamin B12 and its Role in Evaluation of Liver Extracts

to manufacturers and laboratory workers. In spite of repeated attempts extending over the last 30 years, no satisfactory ' laboratory method' has so far been considered worthy of general acceptance. The British Pharmacopoeia lays down specifications for the manufacture of liver extract and only demands that '30 millilitres of the liquid extract of the liver should contain the equivalent of 240 gm. of fresh liver This method naturally does not ensure any check over the specific active principle of liver extract, which is responsible for increasing the number of red corpuscles in the blood of persons suffering from pernicious or other types of anaemia. In the United States, a more