452 URINE 



precisely resemble those of this secretion in the carnivora ; that is to 

 say, the secretion is of a very light amber-yellow tint or almost 

 straw-coloured., has a strong acid reaction, and appears either 

 to contain no lactic acid, or only a very small quantity, while, 

 according to Liebig's experiments, it also appears to be perfectly 

 devoid of hippuric acid. On the other hand, after a course of 

 vegetable diet, a very great portion of the free acid is lost, and 

 during a non-nitrogenous diet it altogether disappears : it contains 

 a large amount of dark- coloured extractive matter, and hence is of 

 a brownish red tint ; it is also somewhat turbid, from the separa- 

 tion of earthy phosphates, or at all events, readily becomes so on 

 boiling; it almost always contains alkaline lactates, with oxalate 

 of lime ; according to Liebig, it is tolerably rich in benzoic acid; 

 as is obvious, from the preceding table, I have never found the 

 uric acid completely absent. 



The influence of indigestible or highly seasoned food, of alcoholic 

 drinks, fyc., on the augmentation of the uric acid in the urine, has 

 been already noticed in vol. i., p. 213. 



The fact that, after prolonged fasting, the urine becomes 

 strongly acid, and poor in solid constituents, but that it always 

 contains some urea, has been already mentioned, and is in part 

 numerically demonstrated in vol. i., p. 163. 



It follows, from my own and Simon's experiments,* that after 

 violent bodily exercise far less water is separated by the kidneys, 

 but that the quantities of free acid, of urea, of phosphates, and of 

 sulphates, in the twenty-four hours' urine, are increased, while those 

 of the uric acid and of the extractive matters are diminished. 



It is scarcely necessary to mention that the quantity of water 

 separated by the kidneys must be influenced by the season of the 

 year, the climate, and the atmospheric temperature; for the most 

 superficial observer can notice this in his own person. Julius 

 Vogel has, however, definitely proved it, by weighing daily for six 

 months the urine that was discharged by the same individual. 

 I believe that my experiments (noticed in vol. i., p. 213) com- 

 pletely overthrow the opinion maintained by Fourcroy, Marcet, 

 and Schultens, that prolonged sweating increases the quantity of 

 uric acid in the urine. 



The urine first passed after the night's rest, the urina sanguinis, 

 is, as is well known, of greater density, a darker colour, and a 



* [We may also refer tlie reader to Percy's experiments on tins point, 

 recorded in p. 169 of the second volume of the translation of Simon's Animal 

 Chemistry, c, E. r.] 



