288 DR. ROBERTS ON THE DIURNAL 
portion of it was highly alkaline as it left the pelvis of the 
kidney. And micturition seems to occur, in the usual 
course, at such intervals as most effectually to prevent the 
alkaline urine of food from being observed unless by an 
unusual accident. The first micturition of the day usually 
takes place on leaving bed, and the urine is highly acid. 
The second does not occur, unless the bowels be emptied 
after breakfast, for some five or six hours; and it includes 
some very acid urine secreted before and immediately after 
breakfast, together with the urine of the morning alkaline 
tide, as well as the secretion with recovered acidity which 
is produced for two or three hours after the subsidence of 
the alkaline tide. Such a urine is sure to be acid, not- 
withstanding an alkaline flow through the kidneys for one 
or two hours. The same thing occurs after dinner. The 
bladder is usually emptied before the meal, and then for a 
couple of hours the urine flows acid. If there be excessive 
potation the urine may require discharging at this period, 
and it will always be found acid. If, on the contrary, 
potation has been restricted, or the system drained of 
water at the time of the meal, the next micturition may 
be delayed an hour or two, so as to cut the alkaline tide 
in half. Even then the urine will be acid, unless the 
depression was unusually great. The next micturition 
may occur after tea, and the recovered acidity of the 
urine would then conceal the alkalinity of the portion 
secreted at the beginning of the period. 
From these remarks it may be gathered that unless the 
product of the alkaline tide be isolated, by emptying the 
bladder before and after its flow, no reliance can he placed 
on observations concerning it. This is, I apprehend, the 
reason why the observations of Beneke and Vogel, and 
probably also those of Dr. Sellers, have failed to support 
the conclusions of Dr. Bence Jones. : 
In Dr. Beneke’s experiments the bladder was not emptied 
