In ordinary proteolytic action, both in the stomach and intestine, it is very apparent that the primary products of proteolysis, the proteoses and peptones, are the chief products formed, and that under normal circumstances the greater portion of the proteid food finds its way from the alimentary canal into the blood, after transformation into one or more of these two classes of products. At the same time, it must be borne in mind that even the acid-albumin formed by pepsin-hydrochloric acid may be absorbed without undergoing further change. The view once held, that the rate of absorption from the alimentary tract stands in close relation to the diffusibility of the products formed, and that non-diffusible substances are incapable of absorption, is no longer tenable. Absorption from the intestine is to be considered rather as a process involving the vital activity of the epithelial cells of the intestinal mucous membrane, where chemical affinities and other like factors play an important part in determining the rate and order of transference through the intestinal walls into the blood and lymph. Thus, we have abundant evidence that native proteids which have not undergone proteolysis may be absorbed from the intestine, at least to a certain extent, provided they have been dissolved; _i. e._, converted into acid-albumin, or alkali-albuminate, by the gastric or pancreatic juice. We have a practical demonstration of this possibility in the early experiments of Voit and Bauer,[199] as well as in many later ones that need not be mentioned here. Further, the recent experiments of Huber[200] have given us quantitative data on the rate of absorption of fluid egg-albumin when introduced into the large intestine in the form of a clyster, showing that even fairly large amounts of a natural proteid may be absorbed without undergoing proteolysis if mixed with a neutral salt, like sodium chloride. To be sure, the rate of absorption is greatly increased when the albumin has been peptonized, but still absorption of the native proteid is possible without the agency of proteolytic enzymes. When, however, large amounts of egg-albumin are introduced into the intestine, albuminuria may result, as you very well know. [199] Ueber die Aufsaugung im Dick und Dünndarm, Zeitschr. f. Biol., Band 5, p. 562. [200] Ueber den Nährwerth der Eierklystiere, Arch. f. klin. Med., Band 47, p. 495. Moreover, it is well known that the proteids of muscle-tissue, in the form of syntonin, may be absorbed from the large intestine without undergoing further hydration. When introduced into the rectum of a hungry dog, the excretion of urea may be at once increased and the animal brought into a condition of nitrogenous equilibrium; absorption taking place from a portion of the large intestine, where proteolysis is never known to occur.[201] [201] Eichhorst: Ueber die Resorption der Albuminate im Dickdarm, Pflüger’s Archiv f. Physiol., Band 4, p. 570.