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Besides the hydrogen ion, as is well known, the ammonium ion is the only cation capable of passing through the membrane of erythrocytes. Possibly the mechanism of this is a simple diffusion; possibly, as assumed by Jacobs (1926-27), it consists in a diffusion of N-H, into the erythrocyte, followed by an exchange of hydroxyl ions from the corpuscle for the anion with which the ammonium ion was combined in the surrounding fluid.If the former possibility holds good, the rate of diffusion of ammonium salts into the red corpuscles may be estimated by means of the coefficient of diffusion of a single salt through the membrane: 2UV U+V"If the diffusion of the salt is based exclusively upon an exchange of anions, the question becomes more complicated, as there is a definable coefficient of diffusion only when there is the same fall in the concentration of the two anions.Taking the simple diffusion of the ammonium ion for a working hypothesis, I have tried to work out an equation from which the rate of the swelling of erythrocytes in solutions of ammonium salts may be expressed by a single numerical quantity, which is to be regarded as a relative diffusion constant for the salt in question. Thus it becomes practicable to compare directly the rates of diffusion of various salts and to study the influence of different factors upon the diffusion rates of individual salts.

Résumé. The pepsin and rennin activities of preparations of dried stomach from the cardia, fundus and pyloric areas respectively have been estimated. In excising material for these preparations, the anatomical distribution of the different gland elements in pig's stomachs (see Meulengracht and Søeborg Ohlsen) has been taken into account. It has been shown that the pepsin and rennin activities are considerable in preparations from the fundus area, but quite small in those from the cardia and pyloric areas. It can presumably be concluded from this that pepsin (and rennin) are secreted by the fundus gland organ, and by that alone. Pepsin (and rennin) and the antianaemic factor are dissociated physiologically and anatomically in the stomach. Consequently pepsin determinations must be used with caution as an indicator of the presence of the antianaemic factor in commercial preparations, but with this proviso the estimation is useful.

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