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'I'he acidity of the secretion was estimated by a test solution 
of caustic soda ; and when it became alkaline, the alkalinity 
was ascertained by dilute sulphuric acid, in the usual way for 
volumetrical analyses. The observations commenced at seven, 
a.m., on leaving bed, when the night urine was discharged. 
At eight o’clock the bladder was emptied again, and thus the 
product secreted from seven to eight was obtained for exami- 
nation. In the same manner, the urine was examined 
separately for each hourly period until noon. From noon 
until dinner the observations were made twm-hourly. After 
dinner the urine was examined every hour until the sixth 
hour after that meal ; and from that till bed-time every two 
hours. 
In this way a minute record was obtained of the varying 
changes of the urine throughout the day and night. 
Two meals a day were taken, breakfast always at eight, 
and dinner generally at two, p.m. ; after which no food was 
taken till breakfast next morning. 
In addition to the degree of acidity or alkalinity of each 
specimen, its exact quantity and specific gravity were also 
duly observed. From the two last the solids separated by 
the kidneys, during each hourly period, were calculated 
according to Dr. Christison’s formula. 
The effect of ordinary mixed food was examined on seven- 
teen days ; the effect of purely animal food (meat, eggs, milk, 
and cheese) on eight days ; and that of purely vegetable food 
(bread, rice, sugar, and fresh vegetables, but no acid or sweet 
fruits) on nine days. 
The results were similar in kind, whatever sort of food was 
taken ; but vegetable food affected the urine less than mixed 
or animal diet. By living several days successively on 
vegetable food, the effect was greatly heightened, and on 
the third day of such diet, a breakfast of two pieces of dried 
toast and two cups of coffee made the urine alkaline in tvvo 
hours. 
