It is thus evident that a certain amount of urea may come from the more or less direct hydrolysis of proteid matter in the intestinal canal, all but the last steps in the process being the result of the ordinary cleavage processes incidental to trypsin-proteolysis. This fact affords additional evidence of the profound changes set in motion by this proteolytic enzyme. It is not, of course, to be understood that all the urea formed in the body has its origin in this manner. Such a method of decomposition taking place in the intestinal tract would be exceedingly unphysiological and wasteful, but we can readily see how such a line of cleavage might result in inestimable gain to the economy in cases where excess of proteid food has been ingested. Under such circumstances, a portion of the surplus might be broken down directly in the intestine into this urea-antecedent, and thus quickly removed from the system with a minimum amount of effort on the part of the economy. Drechsel estimates that about one-ninth of the urea daily excreted may come from the direct decomposition of lysatin, the latter obviously having its origin in trypsin-proteolysis. Another product of trypsin-proteolysis which has long been recognized, although its real nature has not been known, is tryptophan or proteinochromogen. This body is not only a product of the pancreatic digestion of proteids, but it is also formed whenever native proteids are broken down through any influence whatever, the substance coming presumably from the hemi-moiety of the molecule. It is especially characterized by the bright-colored compound it forms with either chlorine or bromine, so that for a long time it went by the mystical name of the “bromine body.” When brought in contact with either of these agents, it immediately combines with them to form a new compound of an intense violet color, termed proteinochrome. This constitutes the usual test for its presence, a little bromine water, for example, quickly bringing out a violet color when added to a fluid containing the chromogen. The body is readily soluble in alcohol, and hence can be easily separated from the primary products of trypsin-proteolysis, such as the proteoses and peptones. Krukenberg considered the substance not a true proteid, but rather a body belonging to the indigo-group; but Stadelmann, who has given the matter a very thorough investigation, comes to the conclusion that it is truly a proteid body, in part closely related to peptone, although in many ways quite different. The following composition of bromine proteinochrome, as determined by Stadelmann,[190] shows the general nature of the compound formed when bromine combines with the chromogen: _A_ _D_ C 49.00 48.12 H 5.28 5.09 N 10.99 11.92 S 3.77 3.10 O 11.01 12.00 Br 19.95 19.77