Abstract
Summary
1. Spreading type assays made on extracts of mammary glands taken from female albino rats pregnant from 3 to 18 days indicated the presence of a spreading factor. The concentration of the factor increased until about the twelfth day followed by a gradual decline. 2. Extracts of mammary glands from normal male and female rats, as well as castrate animals, assayed by the spreading method failed to exhibit any spreading effect at the dilution employed. 3. Turbidimetric assays of mammary gland extract showed that the spreading factor did not hydrolyze the substrate, hyaluronidate. 4. Tests showed that after heating at 60°C for 10 minutes, the spreading factor was still active but inactive after heating at 70°C for 10 minutes.
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