The Abderhalden reaction is a now defunct blood test for pregnancy developed by Emil Abderhalden. In 1909 Abderhalden found that on identification of a foreign protein in the blood, the body reacts with a "defensive fermentation" (in modern terms, a protease reaction) that causes disintegration of the protein. He developed the test in 1912. This test became a subject of contention soon after its development, and a significant body of work was published both in support of and refuting the test's reliability. One such publication concluded "...the individual variations of both pregnant and non-pregnant sera make the results from both overlap so completely as to render the reaction, even with quantitative technique, absolutely indecisive for either positive or negative diagnosis of pregnancy.