408 URINE. 



of the air, exhibited no redness. All these appearances certainly 

 indicate that the pigment of the urine, which, according to 

 Duvernoy* and Scherer, participates in the separation of uric acid, 

 may also contribute to the formation of the ordinary sediment of 

 urate of soda. Even if we are not disposed to regard the extractive 

 matter as a simple solvent, according to the above view, we 

 might yet assume that the neutral urate of soda was dissolved in 

 resh urine that was very rich in uric acid, whilst a little acid 

 might be formed by this metamorphosis of the pigment, which 

 might extract an equivalent of base from the simple urate of soda, 

 and thus give rise to the formation of the bi-urate. (See vol. i., 

 p. 203.) This view is corroborated, in the first place, by the fact that 

 this ordinary sediment certainly does consist of the bi-urate of soda, 

 and in the next, by the fact that in the above described experiment, in 

 which the sediment had been collected on the filter, and it was 

 then attempted to dissolve it in hot water, the filtered fluid did 

 not exhibit an alkaline reaction, although a large portion of 

 crystalline uric acid free from soda remained upon the filter. It 

 requires, however, further experiments to elucidate this much 

 neglected department of zoo-chemistry. 



It must be observed, that Scherer has demonstrated, almost 

 beyond a doubt, by means of several striking experiments, that 

 the metamorphosis of the pigment exerts a great influence on the 

 formation of the sediments of uric acid. We have already shown, 

 in vol. i., p. 216, that, except perhaps in lithiasis, sediments com- 

 posed of free uric acid never occur in freshly passed urine, nor can 

 they be generated by the mere cooling of the urine. Hence I can 

 only regard uric acid sediments as products of the decomposition 

 of the urine after its removal from the animal organism. The 

 different kinds of urine vary solely in respect to the rapidity 

 with which any one kind of morbid, or normal, urine undergoes 

 acid fermentation sooner than another, and thus gives rise to 

 the formation of the insoluble sediments of uric acid. Scherer 

 was the first who recognised and attentively followed this process 

 of acid urinary fermentation. Every normal, non-sedimentary 

 urine, when exposed to the ordinary atmospheric temperature, 

 begins, after a longer or shorter period, to separate uric acid, and 

 to exert a stronger reaction on litmus paper ; we may, moreover, 

 convince ourselves most strikingly of the increase of free acid in 

 the urine by the volumetric method, which corresponds to the 

 alkalimetric. Faintly alkaline urine, such as is passed after 

 * Unters, Uber d, menscbl. Urin. Stuttgart, 1835. 



