362 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 



perfect diffusion l apparatus ; on the removal of the hydrochloric acid, 

 fresh acid is formed by further mass action on the chlorides. The 

 kidneys or sweat glands probably do not so secrete hydrochloric acid, 

 because they are not such perfect diffusion arrangements as the gastric 

 glands, and cannot bring about such a molecular separation as the latter. 



Objections to Malys theory. 1. Modern work has shown that the 

 alkaline reaction of theoretically acid salts is probably due to a hydro- 

 lysis taking place on solution. Thus on dissolving sodium bicarbonate 

 there are formed sodic hydrate and carbonic acid (NaHCO, + H 2 NaOH 

 + H 2 C0 3 ) ; and the sodic hydrate being a powerful base, and the car- 

 bonic acid a weak acid, one equivalent of the base more than balances 

 two of the acid, and the reaction is alkaline. On the other hand, when 

 acid potassium sulphate is dissolved, there is one equivalent in solution 

 of a strong base, and two equivalents of a strong acid, and the reaction 

 is acid. Such an hydrolysis of phosphates of the alkalies also takes 

 place. Trisodic phosphate yields an equivalent of base to one of acid, 

 and the reaction is intensely alkaline ; disodic phosphate yields only two 

 equivalents of base to three of acid, but the reaction is still alkaline ; 

 while monosodic phosphate yields but one equivalent of base to three of 

 acid, and at last the reaction is acid. A mixture of mono- and disodic 

 phosphates in proper proportion would be neutral. In fact, after these 

 salts are dissolved, they no longer exist as such, but there are present in 

 solution bases and acids in certain concentrations, and the reaction of the 

 solution will depend on which of these acts most strongly on the in- 

 dicator. Now the hydrolysing effect on the neutral salts, chlorides, etc, 

 (if such are also present in solution), of these so-called acid salts must 

 closely resemble their effect on the indicator. 



Whether there will be a tendency to formation of hydrochloric acid 

 or not from sodium chloride, will be determined by whether the attraction 

 of the acids (phosphoric and carbonic) for the base is greater or less 

 than the attraction of the bases for the hydrochloric acid. The reaction 

 of the solution of phosphates and carbonates in the plasma is alkaline, 

 which shows that the latter is the case, and that, therefore, there will be 

 no hydrochloric acid formed. 



2. The continuous formation of hydrochloric acid by a reaction 

 between disodic phosphate and calcium chloride is impossible, because it 

 necessitates the formation of insoluble tricalcic phosphate, and as the 

 supply of calcium chloride is small, must soon stop. 



3. Even if it be admitted that there are traces of hydrochloric acid 

 in the blood, there is no reason, if the process be purely one of diffusion, 

 why it should not go on continuously. This it does not do, but ceases 

 when digestion is not going on, and when digestion begins is secreted in 

 such amount that no mere physical diffusion could bring it through the 

 epithelial cells fast enough ; not to speak of separating it from a fluid 

 in which it is supposed to be present in traces only. 2 



1 By a perfect diffusion apparatus (vollkommener Diffusions-apparat] Maly seems to 

 mean here semipermeable membrane ; that is, an arrangement permeable to the hydrochloric 

 acid and not to the other dissolved substances. 



2 Gastric juice contains at least 2 parts per 1000 of hydrochloric acid ; the amount of 

 hydrochloric acid formed by mass action in a solution of 6 parts per 1000 of sodium 

 chloride, and a still smaller quantity of monosodium phosphates, no one has ever attempted 

 to measure, but it must be many thousand times less than this ; so that not only must the 

 hydrochloric acid diffuse with a tremendous velocity, but it must get infinitely more con- 

 centrated in the process of diffusion, which, under purely physical conditions, so far as 

 we know them, is an utter impossibility. 



