VARIATIONS IN THE ACIDITY OF THE URINE. 279 
they enable us to explain certain irregularities and discre- 
pancies which appear when the effect of a meal on one day 
is compared with the effect of a similar meal on another 
day. For it frequently comes to pass that the remote effect 
of a previous meal interferes with, or completely masks the 
immediate effect of a succeeding one. Here, no doubt, 
lies the cause of the slight effect produced by vegetable 
food in the first set (Table IX). The remote effect of the 
highly animalised diet of the previous days masked the 
immediate effect of the meals on the days following. 
It is a marked feature in these experiments, that, al- 
though there was the greatest constancy and certainty in 
the successive changes of reaction, there were very consi- 
derable — indeed the widest — differences in the absolute 
amounts of free acid or free alkali separated by the kid- 
neys at corresponding hours after a meal on different days. 
For example, in Table IV., the acid passed between 
eight and nine a.m. on the first day was more than four 
times greater than on the third day at the same hour; 
and this, although the breakfast on the two days was as 
nearly as possible the same both in quantity and quality. 
Two considerations may be offered in explanation of this 
discrepancy. First, there was the supper on the night 
preceding the first day ; secondly, digestion and absorption 
of the meal was probably going on more rapidly on the 
third morning than on the first, from the comparatively 
empty state of the vessels, consequent on the long pre- 
vious abstinence. 
But these explanations by no means meet all the cases 
of irregularity, as is shown by a comparison of the state 
of the urine from ten to eleven a.m. on the fourth and 
fifth days of the same table. On the fourth the urine was 
neutral at this period, whereas on the fifth it was acid to 
the extent of 0°20 per hour; yet on both days the antece- 
dents, so far as food was concerned, were identical. Doubt- 
