242 DR. ROBERTS ON THE DIURNAL 
of the urine, and to find out some means, if it were pos- 
sible, of reconciling the conflicting facts. The following 
experiments were undertaken with that purpose; and in a 
subsequent portion of the Paper some considerations are 
advanced which go far to account for this want of agree- 
ment. 
All the experiments herein detailed concerned a single 
individual. He was a healthy man, twenty-eight years of 
age, taking moderate exercise, living in most favourable 
hygienic conditions, and weighing 144 lbs. 
In order to ascertain the exact amount of change under- 
gone by the urine after food, it was thought essential to 
collect the secretion at each hourly period succeeding a 
meal, and by measuring its quantity and saturating power 
to obtain data from which the precise amount of free acid 
or free alkali separated per hour by the kidneys could be 
estimated. At periods more remote from meal-times the 
urine was usually collected every two hours. As compared 
with Dr. Jones’s method of merely ascertaining the de- 
gree of acidity or alkalescence per 1000 grains, it had this 
important advantage, that it eliminated the inaccuracies - 
consequent on the great inequality of concentration to 
which the urine is subject from food, drink, exercise and 
sleep, whereby its quantity and aqueousness rise or fall 
immensely, and with great suddenness. 
The following particulars were taken of each urine, and 
arranged in a tabular form : — 
I. The Time of Day during which it was secreted. 
II. The Quantity. This was estimated in a glass vessel 
graduated on the scale of the 1000-grain measure. If the 
period of secretion exceeded or fell short of an hour by 
five, ten, or fifteen minutes, or if the period was two or 
more hours, as during sleep, the hourly rate of secretion 
was exactly calculated from the quantity and the interval. 
The results are arranged in the second columns of the 
