Abstract
The power which serum possesses to inhibit tryptic digestion is a well known phenomenon, but the nature of the process is not well understood. This is evidenced by the fact that the anti-tryptic power of serum has been variously ascribed to the proteins, the lipoids, and the nitrogenous crystalloids of the serum, and more recently to the saponified unsaturated fatty acids present in it.
The observations to be reported were made in the course of a study begun two years ago on the isolation of the different pancreatic ferments. For reasons which will be discussed at another time, the anti-tryptic action of serum was investigated. At first an inquiry was made into the particular substance in the serum which was endowed with the power to inhibit tryptic digestion. Our results were in conformity with those who found that the albumin fraction of the serum proteins was chiefly responsible for the phenomenon. It may be added that other substances contribute to the total inhibitory action of serum. The globulins, for example, possess the power to a limited degree, and only when present in concentration. While studying this phenomenon with whole serum, in great dilution, it was found that the degree of inhibitory action was proportionate to the quantity of albumin present. Under such conditions other substances apparently played no part in the reaction. The inhibitory action obtained from the fatty substances present in the serum is insignificant, when contrasted with the remarkable power which whole serum or its albumin fraction possesses.
The next question investigated was the nature of the inhibitory action. You will recall that when the anti-tryptic action of serum was first observed it was thought to resemble the action of the specific anti-body of the immune system.
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