VIEULENT DISEASES. 177 



microscopic organisms in fermentation, changed the 

 course of these ideas. The ancient medical theory of 

 parasites and living contagia was revived. A German 

 Professor, Dr. Traube, in 1864, put forward, in one of 

 his clinical lectures, a new doctrine of the ammoniacal 

 fermentation of urine. 



' For a long period,' he said, ' the mucus of the 

 bladder was regarded as the agent of the alkaline 

 decomposition of urine. It was supposed that, in 

 consequence of the distension produced by the reten- 

 tion of the liquid, the irritated bladder produced a 

 larger quantity of mucus, and this mucus was re- 

 garded as the ferment which brought about the 

 decomposition of urea, by an innate chemical 

 force. This opinion (which was that of Liebig) can- 

 not hold its ground in presence of the researches of 

 Pasteur. This investigator has demonstrated, in the 

 most decisive manner, that alkaline fermentation, like 

 alcoholic and acetic fermentation, is produced by 

 living organisms, the pre-existence of which in the 

 liquid is the sine qua non of the process.' And Dr. 

 Traube, citing some facts which confirmed the doc- 

 trine of Pasteur, concluded thus : ' Notwithstanding 

 the long retention of the urine, its alkaline fermenta- 

 tion is not produced by an increased secretion of 

 mucus or of pus ; it only begins to develop from 

 the moment when the germs of vibrios find access 

 to the bladder from without, 



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