VARIATIONS IN THE ACIDITY OF THE URINE. 271 
dilution, which sometimes sink the determinations per 
1000 grains almost to zero, although the separation of 
acid at the time is high. In the second place, we avoid 
oscillations arising from the varying activity of the kid- 
neys. 
I shall presently have to call attention to the columns 
showing the hourly discharge of solid urine. It will be 
sufficient here to state, that, after meals, the hourly dis- 
charge of solids rises very considerably, that at periods 
remote from meals it sinks again, and that during sleep it 
falls to a minimum. So great is the oscillation from this 
sole cause that it gives an entirely false complexion to the 
columns indicating the acid separated per hour. It makes 
it appear as if the acidity, after having recovered from the 
first depression consequent on a meal, rose for a few hours 
to an unusual height, and then fell away again a second 
time — as if, in fact, an acid tide succeeded to the alkaline 
tide previously to the subsidence of the reaction to its 
normal level. If the eye be cast along the columns of 
hourly discharge of acid in the various tables, this will be 
seen at a glance. During the hours of continued absti- 
nence after dinner it comes into especial prominence. It 
is seen that when the alkaline tide has subsided, and the 
acid reaction become re-established, there is exhibited for 
about two hours an unusually high rate of discharge; in 
fact higher than at any period of the twenty-four hours ; 
and that after this again there appears a constant fall 
which is maintained and increased during the subsequent 
hours of abstinence and sleep. All the tables concur- 
rently demonstrate this (see Tables I., III., XI. and XV.), 
and without the correction here indicated it would lead to 
an erroneous interpretation of facts. 
Now if we take the solid urine, and calculate its acidity 
per 100 parts, we find that after recovering from the de- 
pression of the alkaline tide the acidity shows no sign of 
