DI8EASE8 OF THE URINARY ORGANS. 131 



It will be observed that, with the exception of oats, none of the 

 grains contain more than two-thirds of the nitrogenous material 

 present in the wheat bran, while in the case of rye and maize there is 

 practically but one-half. Even in the case of oats the albuminoids, 

 which are the more digestible principles, and therefore those that 

 are the most easily and speedily converted into urea, are present only 

 to the amount of two-thirds of that which exists in the wheat bran. 

 With such an excess of ash, of phosphates, and of nitrogenous (urea- 

 forming) constituents in wheat bran, its tendency to favor the forma- 

 tion of calculi is fully explained. It must not, however, be inferred 

 that wheat bran is not a valuable foodstuff. The inference is only 

 that it should be fed with an abundance of water, as a sloppy mash, 

 or in combination with an abundance of roots, potatoes, pumpkins, 

 or other succulent aliment. 



In this connection the presence of magnesia in the food or water 

 must be named as favoring calculous formations in the urinary pas- 

 sages. The explanation is that while the phosphate of magnesia 

 thrown out in the urine is soluble in water, the compound phosphate 

 of ammonia and magnesia is insoluble, and, accordingly, if at any 

 time ammonia is introduced into urine containing the phosphate of 

 magnesia, there is instantly formed the ammonio-magnesium phos- 

 phate, which is as promptly deposited in the solid form. The com- 

 mon source of ammonia in such cases is from decomposition of the 

 urea in fermenting urine. But in order to produce this a ferment is 

 necessary, and therefore, as an additional prerequisite, the presence 

 of bacteria, or fungi, in the urine is essential. These ferments may 

 make their way from without along the urinary passage (urethra), 

 and their propagation in the bladder is greatly favored by the pro- 

 longed retention of urine, as in case of spasm of the neck of the 

 bladder or obstruction by an already existing stone. Another mode 

 of entrance of the ferment is an uncleanly catheter used to draw off 

 the urine. Still another is the elimination through the kidneys of 

 the bacteria of infectious diseases, or of such as, without producing 

 a general infection, yet determine fermentation in the urine. The 

 precipitation is favored not only by the production of ammonia, but 

 also by the formation of viscid (colloid) products of fermentation. In 

 this sense bacteria are most important factors in causing gritty 

 deposits in the urine. 



Another insoluble salt which enters largely into the composition of 

 many urinary calculi of the ox is carbonate of lime. This is derived 

 mainly from the lime in the food and water and from the carbon dioxid 

 formed by the oxidation of the organic acids in the fodder. These 

 organic acids, being composed of carbon, hydrogen, and oxygen (with- 

 out nitrogen), are resolved by the addition of oxygen into carbon 

 dioxid (C0 2 ) and water (H 2 0). The carbon dioxid unites with the 

 lime in the blood to form carbonate of lime, and in this state passes 



