Thromboplastic Activity of Placenta Extract

Abstract

IN the course of an investigation of hormones of human placenta, we came across a substance which showed strong blood-coagulating properties. Freshwater extracts of placenta contain this factor. Their activity diminishes when they are kept at room temperature or in a refrigerator. It is not removed from the extracts by dialysis at 0°C. On filtration through a Seitz filter, the active substance remains on the asbestos fibre. By extracting the filter with distilled water or saline, we obtained a solution possessing the properties of thromboplastin. The resulting slightly opalescent solution is more stable and can be stored for at least one month in a sealed container in a refrigerator without loss of potency. It gives a weak positive reaction with sulphasalicylic acid.