URINARY LITHIASIS. 515 



may resemble coral or may form growths of a rounded, polyliedric or 

 raspberry appearance. Some are hard and resistant ; others friable. 

 They vary in size between that of a grain of sand and a hen's egg or 

 more. A large calculus is usually solitary ; the smaller sizes are often 

 multiple. 



Calculi occur in oxen and sheep, but more particularly in the latter 

 species. They develop slowly Avithout producing any marked external 

 signs, and often it is only when the urethra becomes obstructed and 

 urine is retained that the diagnosis is established. Calculi are rare 

 in females in consequence of the dilatability of the urethra. 



CALCULI IN BOVINE ANIJL^LS. 



Causation. The older writers believed that calculi developed through 

 winter feeding and a stinted supply of water. Nowadays this would not 

 apply to well-managed establishments, water being provided regularly, 

 and winter feeding comprising roots, etc., rich in water. Experience 

 and observation have shown that the chief cause is excessive feeding, 

 calculus formation occurring most frequently in animals which are 

 most richly fed. 



Nevertheless, it would be a mistake to overlook the effects of 

 temperament and constitution. In human medicine the importance 

 of hereditary predisposition and of the special diathesis is undeniable 

 (uric or gouty diathesis). In veterinary medicine the same thing 

 applies, for, apart from rich feeding, it is not uncommon to meet with 

 cases of gravel in animals living under the most diverse conditions, 

 although the issue of the same parents. 



Certain infections of the urinary passages, though trifling at first, 

 or at least of slow development, are also capable of causing mineral 

 deposits in the urinary passages, a fact which Moussu considers to be 

 proved by his success in experimentally reproducing given forms of 

 pyelo-nephritis. 



Symptoms. The symptoms are often overlooked, as long as the 

 calculus deposits affect only the kidneys, their increase in that part 

 not giving rise to alarming symptoms. It is certain that the eventual 

 passage of the calculus through the ureter towards the bladder causes 

 nephritic colic, but this form of colic is little understood, and has 

 never been well described. Writers have simply mentioned cases of 

 colic accompanied by great tenderness in the lumbar region, temporary 

 suspension of the secretion of urine, and more or less marked dysuria. 



Nothing resembling the extremely grave symptoms of nephritic colic 

 in mankind has been described, though probably there is little differ- 

 ence in the complaint as it affects the bovine species. 



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