VARIATIONS IN THE ACIDITY OF THE URINE. 287 
quickened ; more carbonic acid is exhaled, and conse- 
quently more oxygen absorbed into the blood. Those 
persons in whom this increase takes place promptly after 
a meal, and is unusually great, would probably show but 
a feeble alkaline tide, because the oxygen, thus thrown in 
excessive quantity into the blood, would cause increased 
formation of acid, and in this way mask the contrary effect 
of the food. 
3. The quicker the digestion and the absorption of a 
meal, the greater cwteris paribus would be its depressing 
effect on the acidity of the urine. 
It seems not unlikely that the two last mentioned causes 
determine by their mutual relation in an especial manner 
the degree of intensity assumed by the alkaline tide. A 
rapid absorption of a meal and a small amount of respi- 
ratory acceleration would present the combination most 
favourable to an intense depression of the urinary acid. 
On the contrary, a slow absorption of a meal and a prompt 
exaltation in the respiratory functions would so balance the 
opposing tendencies that the reaction of the urine would 
suffer only a minimum of depression. 
These modifying circumstances apply not only to differ- 
ences between individuals, but, in a minor degree also, to 
differences in the same individual at different times. 
This seems the proper place to offer some considerations 
which may explain why alkaline urine after meals is not 
oftener met with in actual experience; and whence arise 
the grave discrepancies in the experience of different 
observers in this country and in Germany. 
It is essential, in order to trace the effect of a meal, fo 
examine the urine at short intervals. For if this be neg- 
lected the acid product secreted before and after the 
period of depression becomes mixed in the bladder with 
_the urine of the alkaline tide, and when the whole is 
ejected by micturition it is found acid, even although a 
