
1905.| in Gastric Contents in Malignant Disease of Organs. 149 
to orientate us as to the cause of the reaction, and to furnish some conception of 
how acid or alkali can be secreted from the same common fluid. 
Now other things being equal in the way of permeability and affinity of the cell 
concerned in secretion, for the acid or alkali causing ions, it is evident that the 
power to secrete an acid or alkaline secretion will depend upon the concentration 
of these ions in the fluid which supplies the cell, that is the blood plasma. 
But it must be carefully borne in mind that this factor cannot be obtained by 
titration of the plasma to neutrality in presence of an indicator. This does not 
give the effective concentration of the ions in solution, as is shown experimentally 
by the fact that the figure so obtained varies not only in amount but in algebraic 
sign with the indicator used, blood plasma being alkaline to “di-methyl,” methyl 
orange, and litmus, and acid to phenol-phthaléin, and urine alkaline to the two 
former and acid to the two latter indicators. 
The reason why such titration does not give the effective acidity or alkalinity is 
that an equilibrium is disturbed as the alkali or acid respectively are added.* 
Suppose, for example, that we are titrating the alkalinity of blood serum to litmus 
by means of a standard acid solution, then as the acid is added the hydroxyl ions 
are reduced by combining with the hydrogen ions of the added acid to form water. 
As a result equilibrium is disturbed, more hydroxyl ions are formed by breaking 
up of the undissociated carbonate or phosphate molecules to replace those used up, 
and the alkaline reaction persists until all the carbonate or alkaline phosphate has 
been used up. 
Hence no knowledge is obtained by titration, of the real effective alkalinity at 
any instant, as determined by the hydroxyl ion concentration at that instant, but 
instead the titration figure gives the amount of acid necessary to reduce the 
bicarbonate and disodic phosphate to a certain condition with regard to the 
particular indicator used ; that is, we do not get the value of the concentration of 
the hydroxyl ions when we began the titration, but instead, the amount of acid 
necessary to reduce the concentration of the hydroxyl ions to a dilution, at which 
_ the particular indicator in use is no longer affected, and this figure may bear no 
relationship to the concentration of hydroxy] ions, or effective alkali in the blood 
serum. 
The consideration of this subject has been given at some length, because it 
affects not only the method we have here in view for determining the degree of 
effective acidity of the gastric contents, and incidentally the nature of the acid 
present, but casts a light upon the bearing of the absence or diminution of the 
* The formula for equilibrium is deduced as follows :—Suppose we have a solution 
represented by the equation KOH = K +08, and let the concentrations of the molecules 
in solution be represented by CKOH, Cx, and Cou, then the tendency for K and OH to 
combine will evidently be proportional to the product Cx - Cou, and the tendency of KOH 
to split up into ions will be proportional to Cxou. For equilibrium these two tendencies 
must balance, and hence Cx-Con = K :Cxon, accordingly if one concentration varies 
such as that of Con on the addition of an acid, then the other concentrations must 
change correspondingly, that is, more KOH must dissociate. 
