To determine whether a collection of fluid in a serous cavity is of malignant origin is often a matter of considerable difficulty. The specific gravity and albumin content are of little or no value. The usual bloody nature of the fluid is not diagnostic. The only reliable means of detecting a malignant neoplasm from a study of puncture fluids alone has been the finding of mitotic cells — very rarely of tissue fragments — in the stained sediment, and such cells are often lacking.
In view of the demonstration of a proteolytic enzyme or enzymes in carcinomata and sarcomata, it occurred to me that the ferment, if secreted into a serous fluid, might disclose its presence by an increase in the quantity of incoagulable nitrogen. With this idea, the present study was undertaken.
That malignant tumors contain one or more proteolytic enzymes was first suspected by F. Müller.1
MORRIS RS. THE INCOAGULABLE NITROGEN OF PUNCTURE FLUIDS, WITH SPECIAL REFERENCE TO CANCER: A PRELIMINARY NOTE. Arch Intern Med (Chic). 1911;VIII(4):457–462. doi:10.1001/archinte.1911.00060100042004
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