Diseases of the Urinary Organs. 305 



the formation of urinary calculi, may be added all such as 

 favor concentration of the urine. Thus scarcity of drink- 

 ing water, excessiTe loss of liquid by the bowels or skin, 

 (diarrhoea, dysentery, etc.,) dry winter feeding on hay and 

 grain, feverish states in which little urine is secreted, and 

 hard waters appear to have this effect. The last named 

 cause is not generally credited by physicians biit its coin- 

 cidence with the prevalence of stone is exceedingly com- 

 mon. 



Mode of Formation. The first requisite is that some 

 solid body should exist as a nucleus around which layer 

 after layer is crystallized, and hence the stone is always 

 composed of a series of concentric layers. The nucleus 

 may consist in a particle of mucus, fibrine or blood, a 

 crystal deposited from over-saturated urine, or even a for- 

 eign body introduced from without. I have seen a large 

 calculus in the kidney of a deer formed around a piece of 

 wood which must have penetrated the kidney and broken 

 off, while the wound by which it entered had healed up. 



Appearance. Calculi vary much in character but the 

 most marked varieties are the smooth stones formed by 

 carbonates, oxalates, phosphates and silica, and the 

 rough jagged crystalline specimens of ammonio-magnesian 

 phosphates. 



Renal Calculi. Those found in the kidney are usually 

 moulded in the pelvis, though I have found many like 

 small lentils in dilatations of the microscopic tubes in the 

 substance of the gland. Cattle fed on dry hay and grain, 

 during winter, rarely want small yellow crystaUine masses 

 in the pelvis. Even when so large as to distend the pel- 

 vis and weigh several ounces they are not always incom- 

 patible with good health and aptitude to fatten. When 

 so large or rough as to produce manifest disorder, this 

 appears as irritation of the kidneys, tender loins, stiff 

 straddling gait, etc., with the passage of microsc ipic crys- 

 tals, and perhaps blood or pus in the urine. In cattle and 

 sheep the salts fi'om the concentrated urine usually crys- 

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