80 



STRICTURE OF THE URETHRA. 



This is a permanent narrowing of the urethra at a given point, the 

 result of i^revious inflammation, caused by the passage or arrest of a 

 stone or gravel, by strong astringent injections in the early non-secret- 

 ing stages of urethritis, or by contraction of the lining membrane 

 occurring during the healing of ulcers in neglected inflammations of 

 that canal. The trouble is shown by the passage of urine in a fine 

 stream with straining, pain, and groahing, and by frequent painful 

 erections. It must be remedied bj^ 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 will 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 — GRAVEL. 



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

 cipitated 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. Their composition is therefore determined in differ- 

 ent animals by the salts and other constituents found dissolved in the 

 healthy urine, and by the additional constituents which may be thrown 

 off in solution in the urine in disease. In this connection it is impor- 

 tant to observe the following analysis of the horse's urine in health : 



Water 918.5 



Urea - 13.4 



Uric acid and urates - _ _ 0. 1 



Hippuric acid 26. 4 



Lactic acid and lactates 1.0 



Mucus and organic matter 23. 



Siilpbates (alkaline) r 1.2 



Phosphates (lime and soda) 0.2 



Chlorides (sodium) 1.0 



Carbonates (potash, magnesia, lime) 16. 



1000. 



The carbonate of lime, which is present in large amount in the urine 

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

 forms in the j)assages after secretion, and its microscopic rounded 

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

 material which constitutes the soft, white, pultaccous mass that some- 

 times fills the bladder to repletion and requires to be washed out. In 

 liay-fed horses carbonates are still abundant, while in those mainlj'- 

 grain-fed they are replaced by hippurates and phosphates — the prod- 

 ucts of the wear of tissues — the carbonates being the result of oxida- 

 tion of the vegetable acids in the food. Carbonate of lime, therefore, 

 is a very common constituent of urinary calculi in lierbivora, and in 

 many cases is the most abundant constituent. 



