76 DISEASES OF THE BLADDER 



during its abode in the uiinarj passages. This decomposition is similar 

 to that which takes place in urine when allowed to stand exposed to 

 the air. There is at first an acid fermentation. The coloring and ex- 

 tractive matter of the urine become converted into lactic acid, so that 

 the urea is liberated from its soluble combinations, and is precipitated. 

 The acid fermentation is followed by an alkaline one. The urea is 

 converted into carbonate of ammonia, and, by a combination of the 

 ammonia with the phosphate of magnesia, an ammonio-magnesian 

 phosphate is formed the so-called triple phosphate. The ferment 

 which excites this decomposition in the urine, while yet in the bladder, 

 is the mucus resulting from vesical catarrh ; but, according to ScJierer, 

 besides this, the mucus plays another and most important role in the 

 formation of calculi, by forming a cement to hold the sediment together, 

 since coagula of mucus form the nuclei of most stones, to which the 

 deposits afterward adhere by accretion. According to the theory of 

 Scherer, the formation of stones, which consist of a nucleus of uric acid 

 enclosed in layers of phosphates, is as follows : As long as the acid 

 fermentation of the urine continues, uric acid is precipitated ; when, 

 however, the catarrh has continued for some time, and, perhaps, has 

 become aggravated by the presence of a calculus in the bladder, alka- 

 line fermentation sets in, and the phosphates are thrown down. 



According to a very brilliant hypothesis of Meckel, the formation 

 of precipitates is not requisite for the production of a urinary calculus. 

 He claims that almost all stones consist originally of oxalate of lime, 

 and are formed as follows : The mucous membrane of the urinary pas- 

 sages becomes the seat of a specific catarrh, called by Meckd the 

 "stone-forming catarrh" (stein-bildenden catarrh). In this catarrh a 

 tough adhesive mucus is secreted, which has a tendency to acid fer- 

 mentation, and in which oxalate of lime appears when such fermenta- 

 tion occurs. At first this oxalate-of-lime mucus is of a gelatinous con- 

 sistence. Gradually, however, it takes up more and more oxalate of 

 lime from the decomposed urine, and thus, growing more and more 

 firm, finally becomes stony. As long as the urine remains decidedly 

 acid, the stone enlarges, from the accretion and petrifaction upon it of 

 fresh layers of oxalate-of-lime mucus. If the urine afterward become 

 alkaline, the stone no longer grows from " apposition," but from " in- 

 tussusception," combined with a " metamorphimus," that is to say. 

 the oxalate of lime is at first displaced by uric acid, and urate of am 

 monia, and afterward by the phosphates. In this manner an oxalic 

 calculus becomes converted into a phosphatic calculus. 



To attempt to point out all the flaws in each of these theories, and 

 the various objections which might be advanced against them, would 

 take too long. Among other matters, the fact still remains unex- 



