286 DR. ROBERTS ON THE DIURNAL 
except by greatly multiplied observations conducted on the 
principle of hourly determinations. But the facts at pre- 
sent known warrant the statement, that at least some 
healthy persons, whose urine presents no appreciable 
peculiarity, suffer constantly a diminished acidity of urine 
after meals, and that the secretion may flow alkaline and 
turbid for four and six hours daily without the least 
evidence of impaired function. 
I am disposed to believe that the depression of the 
acidity of the urine after a meal is of universal occur- 
rence ; but, at the same time, observation leads me to con- 
clude that there are very great differences in the degree 
or intensity of the phenomenon in different individuals — 
these differences arising, apparently, from fixed peculiari- 
ties of constitution. Without pretending to be able to 
point out all of these, or to estimate their influence, the 
following may be indicated as probably tending to pro- 
duce that effect. 
1. The cutaneous transpiration varies greatly in differ- 
ent persons. Those with an active skin eliminate a large 
amount of acid by the cutaneous surface, and consequently 
have less for removal by the kidneys. In such persons 
the alkaline tide might be expected to flow with greater 
intensity than where the skin is habitually dry and torpid. 
The sweat seems incapable of ever changing from acid to 
alkaline, for I have invariably found it sour, even when 
the urine has been rendered strongly and uninterruptedly 
alkaline by bicarbonate of potash for four and five weeks 
continuously. 
2. The respiratory capacity of individuals varies. This 
bears on the present question in this way. Recent obser- 
vations, especially those of Dr. E. Smith,* show that 
shortly after a meal the respiratory function is materially 
* See his Papers read before the Royal and Medico-Chirurgical Societies 
during the present year, 1859. 
Neate be Dae 
