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JAMA. 1916;LXVI(8):559-560. doi:10.1001/jama.1916.02580340015007.
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This paper concerns an empiric study of the method for the determination of pregnancy by utilizing the urinary enzyme called forth by the development of the placenta as outlined by Malone.1

In the first place, it is possible to urge the following general criticisms against the method:

  1. It has been quite conclusively shown by qualitative methods in the hands of Peiper,2 Plaut,3 Jobling and Petersen,4 and others, that the enzyme occurring in the blood, which Abderhalden utilized as a test for pregnancy by the color reaction with ninhydrin, when applied to the dialysate from a digest of blood containing this enzyme and the specific substrate placenta, is not a specific one, and quantitative methods by Van Slyke5 have demonstrated this to be true to a degree beyond question.

  2. Two sources exist for the appearance of proteolytic enzymes in normal urine, namely, excreted enzymes from the subject, and, secondly, those


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