DISEASES OF THE UEINAKY ORGANS. 139 



has formed and grown tends to dissolve out the more soluble of its 

 component parts, and thus to destroy its density and cohesion at all 

 points, and thereby to favor its complete disintegration and expul- 

 sion. This explains why cattle taken from a herd on magnesian 

 limestone in spring, after the long, dry feeding of winter, usually 

 have renal calculi, while cattle from the same herd in the fall, after 

 a summer's run on a succulent pasture, are almost always free from 

 concretions. The abundance of liquid taken in the green feed and ex- 

 pelled through the kidneys and the low density or watery nature of 

 the urine have so opened the texture and destroyed the density of 

 the smaller stones and gravel that they have all been disintegrated 

 and removed. This, too, is the main reason why benefit is derived 

 from a prolonged stay at mineral springs by the human victims of 

 gravel. If they had swallowed the same number of quarts of pure 

 water at home and distributed it at suitable times each day, they 

 would have benefited largely without a visit to the springs. 



It follows from what has been just said that a succulent diet, in- 

 cluding a large quantity of water (gruels, sloppy mashes, turnips, 

 beets, potatoes, apples, pumpkins, ensilage, succulent grasses), is an 

 important factor in the relief of the milder forms of stone and gi-avel. 



Prevention. — Prevention of calculus especially demands this sup- 

 ply of water and watery rations on all soils and in all conditions in 

 which there is a predisposition to the disease. It must also be sought 

 by attempts to obviate all those conditions mentioned above as causa- 

 tive of the malady. Sometimes good rain water canTje furnished in 

 limestone districts, but putrid or bad-smelling rain water is to be 

 avoided as probably more injurious than that from the limestone. 

 Unsuccessful attempts have been made to dissolve calculi by alkaline 

 salts and mineral acids, respectively, but their failure as a remedy 

 does not necessarily condemn them as preventives. One dram of 

 caustic potash or of hydrochloric acid may be given daily in the 

 drinking water. In diametrically opposite ways these attack and 

 decompose the less soluble salts and form new ones which are more 

 soluble and therefore little disposed to precipitate in the solid form. 

 Both are beneficial as increasing thie secretion of urine. In cases in 

 which the diet has been too highly charged with phosphates (wheat 

 bran, etc.), these aliments must be restricted and water allowed ad 

 libitum. If the crystals passed with the urine are the sharp an- 

 gular (octahedral) ones of oxalate of lime, then the breathing 

 should be made more active by exercise, and any disease of the lungs 

 subjected to appropriate treatment. If the crystals are triangular 

 prisms of ammonia-niagnesium phosphate or starlike forms with 

 feathery rays, the indications are to withhold the feed or water that 

 abounds in magnesia and check the fermentation in the urine by 

 attempts to destroy its bacteria. In the latter direction plenty of 



