1835.] on Urine. t 



being now evaporated to dryness, and a drop of sulphuric 

 acid let fall upon the small saline residue, a smell was 

 emitted strongly urinous, but mixed with a sensible odour 

 of vinegar. From this experiment I conclude that urine 

 does contain a minute portion of acetic acid. But it is pro- 

 bable that it contains also another volatile acid in small 

 quantity to which the peculiar odour of urine is owing, 

 as Berzelius supposed. Whether this acid be lactic we 

 have no data to decide. 



Urine contains always some uric acid which separates in 

 minute crystals when the urine is mixed with a little nitric 

 acid and set aside for some time in an open glass vessel. 

 Berzelius states the amount of this acid in urine at y^Voth 

 part of the weight. By my experiments to be stated after- 

 wards, it appears that 1000 parts of urine of the specific 

 gravity 1-0185 let fall 0*242 of uric acid when mixed with 

 nitric acid. Now, Dr. Prout has shewn that uric acid does 

 not dissolve in 10,000 times its weight of water, but that 

 urate of ammonia is soluble in about 500 times its weight 

 of that liquid. Hence, he infers that the uric acid in that 

 liquid must be in the state of urate of ammonia. Biit urate 

 of ammonia reddens vegetable blues; hence, the acidity of 

 urine may be partly owing to the presence of this salt. 



Urine is probably the most complex liquid in the animal 

 economy. It is obviously secreted from blood in order to 

 be thrown out of the system, and must, therefore, hold 

 in solution various substances extracted from the blood, in 

 order to bring that liquid into a state fit for the various 

 purposes of assimilation and secretion to which it is applied. 

 Blood consists essentially of water, holding in solution 

 albumen, fibrin and hematin ; it contains also minute quan- 

 tities of soda and perhaps of potash, partly united to albu- 

 men and partly to muriatic acid. It contains likewise 

 common salt. 



The albumen seems to contain, in some state of combi- 

 nation, phosphorus, sulphur, and traces of calcium and 

 magnesium. These substaAces exist in albumen probably 

 because they are useful to some parts of the animal 

 economy. Thus they seem to be deposited in considerable 

 quantity in the brain, but for the other parts of the animal 

 body they are doubtless pernicious, and therefore are ab- 



