Studies on diffusing factors. Active preparations from mammalian testicle and their biological assay

Abstract

The area of skin over which an intracut. injected fluid spreads depends upon the conc. of diffusing factor in the injected soln. These areas are easily detected when the injected fluid is colored by the addition of Hb. A method is described whereby successive tenfold dilutions of diffusing factor can be differentiated. Rabbits are used as exptl. animals. The fact that the diffusing factor precipitates in an alkaline medium, but not in a neutral one, when Pb acetate is added to aq. extracts of bull''s testicles was utilised for the prep. of concentrates.