FERMENTATION OF THE URINE. 409 



vegetable food which is rich in alkalies, or after several doses of 

 acetate or tartrate of potash, acquires, after a short time, an acid 

 reaction, which increases so much under favourable conditions, that 

 any turbidity, which may have arisen from the separation of earthy 

 phosphates, disappears, and crystals of uric acid are separated. 

 Scherer, and subsequently to him, many other observers, have 

 noticed that jaundiced, brownish yellow, faintly acid urine becomes 

 strongly acid, and that, in place of this colour, it assumes a green tint, 

 owing to the peculiar action of the free acid on the bile-pigment. 



The duration of the acid fermentation of the urine extends, 

 according to Scherer, to four or five days, although, in a tem- 

 perature of from 10 to 20 C., I have seen the acid of the urine 

 increase for two or three weeks, and then often not disappear 

 until after a period of six or eight weeks. Scherer explains 

 this process on the supposition that the mucus of the bladder is a 

 fermenting body, and that the extractive pigment is the substance 

 metamorphosed into lactic acid. I have, however, frequently 

 observed, as Liebig had previously done, that acetic acid is also 

 present. Scherer's view derives support from the fact that the 

 acid fermentation of the urine may be impeded, or interrupted, by 

 most of the conditions which in other cases obstruct fermentation, 

 as, for instance, by the addition of a little alcohol, by boiling the 

 urine (when the formation of an acid is retarded for a prolonged 

 period), and finally, by removing the mucus by filtration. The 

 influence of the latter is also obvious, from the circumstance 

 already mentioned at p. 398, that a species of fermentation- 

 globules, or yeast-fungi, are generated in and from the mucus 

 during the process of acid fermentation. I must again draw atten- 

 tion to the possibility that oxalate of lime may be formed, or, at 

 all events, separated during this process of fermentation ; at all 

 events, the close connection between the separation of uric acid 

 and the formation of this salt, seems to be proved by the fact that 

 most samples of urine, whether sedimentary or non-sedimentary, 

 exhibit no trace of the presence of oxalate of lime, when examined 

 under the microscope, as long as they are fresh, although some of 

 the known crystals of oxalate of lime may be detected as soon as 

 the uric acid crystals are formed. Indeed, the abundance of such 

 crystals in morbid urine is proportional to the rapidity with which 

 acid fermentation is induced, and the consequent early deposition 

 of free uric acid. 



From the fifth day to the second or third week after the dis- 

 charge of the urine, the free acid begins gradually to diminish ; 



