of the vessel-wall, and according to Starling it is probable that a preponderating part is played by the endothelial cells of the renal capillaries. [230] Starling: Contributions to the Physiology of Lymph Secretion, Journal of Physiol., vol. xiv, p. 131. In view of all these statements, it is very evident that proteoses and peptones once outside the limits of the alimentary tract may be passed about from organ to organ and from secretion to secretion, inducing changes here and there in their course, but suffering very little change themselves. The main efforts of the system are directed to the removal of these unwelcome strangers as speedily as possible, for their marked physiological action renders them somewhat dangerous visitors. As normal products of digestive proteolysis, they are never found beyond the limits of the gastro-intestinal canal, but undergo retrogression in their passage through the epithelial cells of the intestinal wall, being presumably converted thereby into serum-albumin,[231] which can be directly utilized for the nutrition of the body; a conversion which is plainly dependent upon certain inherent qualities of the living epithelial cells, and is doubtless of the nature of a dehydration. [231] See Kronecker and Popoff: Ueber die Bildung von Serumalbumin im Darmkanale, Du Bois-Reymond’s Archiv f. Physiol., 1887, p. 345. Also Nadine Popoff, Zeitschr. f. Biol., Band 25, p. 427. End of Project Gutenberg's On Digestive Proteolysis, by R. H. Chittenden