VARIATIONS IN THE ACIDITY OF THE URINE, 239 
made about two hours after the meal, and the next about 
three hours later. The urine of sleep and of the following 
morning were also separately examined. As a rule, about 
twelve distinct observations were made in each period of 
twenty-four hours. The effect of ordinary mixed food, of 
purely animal and of purely vegetable diet, was investi- 
gated during separate days on which one or other class of 
diet was exclusively used. He sums up his results in the 
following propositions : — 
I. “As regards the variations of the acidity of the urine 
for three days on mixed diet. The acidity soon after food 
was found to decrease and to attain its lowest limit from 
three to five hours after breakfast and dinner; sooner 
however after breakfast than after dinner. The acidity 
then gradually increased and attained its highest limit 
just before food. If no food was taken the acidity of the 
urine did not decrease, but remained nearly the same for 
twelve hours. It fell immediately after food was taken. 
Il. “ When animal food only was taken, the diminution 
of the acidity after food was more marked and more last- 
ing than when a mixed diet was taken; and the acidity 
before food rose rather higher with a mixed diet than it 
did with animal food. 
Ill. “ When vegetable food only was taken the contrast 
with animal food was very marked. The urine did not 
decrease in acidity to the same degree; though it became 
neutral it did not become highly alkaline. The increase 
in the acidity of the urine was by no means so marked as 
the decrease of the alkalescence. The acidity of the urine 
was rather higher with the vegetable food than it was with 
animal food. 
IV. “The result of these experiments is, that the acidity 
of the urine is always changing, and that the changes de- 
pend on the state of the stomach. When much acid is in 
the stomach the acidity is then diminished. As the acid 
