1905.] wn Gastric Contents in Mahgnant Disease of Organs. 151 
The flask is then placed for a definite time in a thermostat at a temperature of 
45° C. (we have used a period of eight hours, but a shorter period would suffice), 
and at the end of the period the contents of the flask are titrated again, the 
increase in the amount of alkali required for neutralisation gives the amount of 
acetic acid set free by the action of the hydrogen ions of the gastric contents 
during the interval, and hence an indication of the concentration of these ions. 
A simple calculation then gives the concentration of the hydrogen ions. For 
the purposes of this calculation, the total amount of acetic acid capable of being 
set free from the 0°5 c.c. of methyl-acetate added is required, and to obtain this 
a control is made in which deci-normal hydrochloric acid is allowed to act on 
methyl-acetate in the same concentration until the titration gives a constant 
figure for 5 c.c. of the mixture. This figure can be obtained once for all for any 
series carried out about the same time with the same sample of methy]-acetate.* 
A comparison of the results given in the table of the titrations for acetic acid, 
formed from the methyl-acetate in the cases of malignant disease, as compared 
with those in the case of the normal control specimens, demonstrates clearly the 
value of the method, and shows the great contrast between the cases of malignant 
disease and the others. 
The equation giving the velocity constant of the reaction (K), which is 
proportional in each case to the concentration of the hydrogen ions, takes the 
form— | 


where ¢ is the time, expressed in minutes, A is the amount of methyl-acetate 
available for hydrolysis in the beginning, and z the amount of methyl-acetate 
hydrolysed at the end of the time 7. The column in the table gives the values 
of K x 10°, to which the concentrations of hydrogen ions, or the effective acidities 
are proportional, and the last column gives the percentage concentration reckoned 
as effective hydrochloric acid, by comparison with the constant for a deci-normal 
solution (0°365 per cent.) of hydrochloric acid. 
Deductions from the Results given wn the Table. 
1. The fotal acidity in malignant disease, wherever situated, is, as a rule, 
very low. In the 17 cases recorded, the total acidity only rises above 01 per 
cent. in four cases (Nos. V, VI, XI, XVI), and reaches the normal amount of 
approximately 0:28 per cent. in one case only (No. XVI). In the ereat 
majority of the cases one or two drops of deci-normal alkali, added to 10 «c., 
is sufficient to render the reaction alkaline to phenol-phtheléin. In the few 
eases where the total acidity rises above a trace only, the other tests 
* The methyl-acetate should be as pure as possible, give practically no acetic acid on 
titration alone, and a control as indicated above should be carried out at intervals, if the 
series of experiments is a prolonged one. 
