With relatively large amounts of proteid, we may have half or even quarter saturated proteid molecules, in which the weakness of the combined acid is far more pronounced than in the case of the fully saturated molecule. Such a condition of things must obviously exist in the early stages of gastric digestion. With an excess of proteid matter in the stomach, some time must elapse before the secretion of hydrochloric acid will be sufficient to furnish acid for all of the proteid matter present, yet pepsin-proteolysis does not wait the appearance of free acid. Indeed, the proteid matter may not have combined with more than half its complement of hydrochloric acid before digestive proteolysis is well under way. I have made many analyses of the stomach-contents after test meals, and under other conditions, where no free acid could be detected by the tropaeolin test, or better, by Günzburg’s reagent (phloroglucin-vanillin), although phenolphthalein as well as litmus showed strong acid reaction, and yet not only could acid-albumin be detected in the filtered fluid, but likewise proteoses and peptones. In other words, pepsin-proteolysis can proceed in the absence of free hydrochloric acid, although not at the same pace. Hence, proteoses and even peptones may make their appearance in the stomach-contents at a very early period of digestion, _i. e._, the final products of proteolysis may be found in a mixture containing even a large proportion of wholly unaltered proteid, and obviously at an early stage in the process. Expressed in other language, a portion of the first formed acid-albumin or syntonin may be carried forward by the digestive process to the secondary proteose and peptone stage, before the larger portion of the ingested proteid food has even combined with sufficient acid to insure the complete formation of acid-albumin. This introduces another factor, to be referred to later on, viz., the relative combining power of different forms of proteid matter, especially the proteoses and peptones, as contrasted with native proteids. In proof of the statement that pepsin-proteolysis can proceed in the absence of free hydrochloric acid, provided combined acid be present, allow me to cite one or two experiments bearing on this point. A perfectly neutral solution of egg-albumen, containing 0.8169 gramme of ash-free albumin per 10 c.c. of fluid, was employed as the proteid material. In order to completely saturate the proteid contained in 20 c.c. of this neutral albumen solution, 50 c.c. of 0.2 per cent. HCl were required. Two mixtures were then prepared as follows: _A._ Twenty c.c. of the neutral albumen solution + 50 c.c. 0.2 per cent. HCl + 30 c.c. of a weak aqueous solution of pepsin, perfectly neutral to litmus. This mixture gave only the faintest tinge of a reaction for free acid when tested by Günzburg’s reagent.