274 DR. ROBERTS ON THE DIURNAL 
o’clock, that is, within forty minutes after the conclusion of 
the meal. The urine, however, never became alkaline, nor 
even neutral, so soon. During the succeeding hour, from 
nine to ten, the alkaline tide usually culminated; but in 
about a third of the cases the point of least acidity was 
not reached until eleven o’clock. Then the tide turned ; 
and from eleven to twelve the urine was found fast re- 
covering its reaction, and about one the normal level was 
generally attained. 
But although the acidity after breakfast was depressed 
for a period of from four to five hours, it was not absolutely 
alkaline usually for more than one hour; generally from 
nine to ten. Not unfrequently, however, it continued 
alkaline, and even increased in alkalescence, until eleven ; 
and on one occasion it continued alkaline for three hours, 
that is, until noon. 
After dinner, which usually occupied half an hour, the 
acidity maintained itself through the first hour (that is, 
the hour at the beginning of which dinner was taken), but 
declined during the second in varying degrees on different 
days; and on five occasions the urine became alkaline. 
During the third, fourth and fifth hours the alkaline tide 
ran in its greatest strength. On the third and fourth 
hours the urine was always (with two exceptions) found 
alkaline when the meal had been of mixed food or animal 
diet. On the fifth hour it was also nearly always alkaline, 
but not so invariably so as on the two preceding ones. At 
the end of the next (sixth) hour the tide had generally 
turned and the acid reaction been restored. This change 
appeared often to take place with considerable suddenness, 
and the rise of the acidity went on with such celerity that 
in two hours (that is, at the end of the seventh hour) it 
had reached the ordinary standard. Three hours was the 
usual duration of the alkalescent state of the urine after 
dinner ; sometimes two hours, more rarely four hours, and 
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