154 DISEASES OF THE HORSE. 



erections. It must be remedied by mechanical dilatation, with cathe- 

 ters just large enough to pass with gentle force, to be inserted once a 

 day, and to be used of larger size as the passage wdll admit them. 

 The catheter should be kept perfectly clean and washed in a borax 

 solution and well oiled before it is introduced. 



URINARY CALCULI (STONE, OR GRAVEL). 



These consist in some of the solids of the urine that have been 

 precipitated from the urine in the form of crystals, which remain 

 apart as a fine, powdery mass, or magma, or aggregate into calculi, or 

 stones, of varying size. (See PL XL) Their composition is there- 

 fore determined in different animals by the salts or other constitu- 

 ents found dissolved in the healthy urine, and by the additional con- 

 stituents which may be thrown off in solution in the urine in disease. 

 In this connection it is important to observe the following analysis 

 of the horse's urine in health : 



Water 918. 5 



Urea 13. 4 



Uric acid and urates . 1 



Hippuric acid 26. 4 



Lactic acid and lactates 1.2 



Mucus and organic matter 22.0 



Sulpliates (alkaline) 1.2 



Phosphates (lime and soda) . .2 



Chlorids (sodium) 1.0 



Carbonates (potash, magnesia, lime) 16.0 



1000.0 



The carbonate of lime, which is present in large quantity in the 

 urine of horses fed on green fodder, is practically insoluble, and 

 therefore forms in the passages after secretion, and its miscroscopic 

 rounded crystals give the urine of such horses a milky whiteness. It 

 is this material which constitutes the soft, white, pultaceous mass that 

 sometimes fills the bladder to repletion and requires to be washed 

 out. In hay- fed horses carbonates are still abundant, while in those 

 mainly grain-fed they are replaced by hippurates and phosphates — 

 the products of the wear of tissues — ^the carbonates being the result 

 of oxidation of the vegetable acids in the feed. Carbonate of lime, 

 therefore, is a very common constituent of urinary calculi in herbi- 

 vora, and in many cases is the most abundant constituent. 



Oxalate of lime, like carbonate of lime, is derived from the burning 

 up of the carbonaceous matter of the feed in the system, one impor- 

 tant factor being the less perfect oxidation of the carbon. Indeed, 

 Fiistenberg and Schmidt have demonstrated on man, horse, ox, and 

 rabbit that under the full play of the breathing (oxidizing) forces 

 oxalic acid, like other organic acids, is resolved into carbonic acid. 



