DISEASES OF THE UEINAHY ORGANS. 129 



common in working oxen, which are called upon to exhale more 

 water from the lungs and skin than are the slop-fed and inactive 

 cows. Little Avater being introduced into the body with the feed 

 and considerable being expelled with the breath and perspiration 

 in connection with the active life, the urine becomes small in 

 amount, but having to carry out all waste material from the tissues 

 and the tissue-forming feed it becomes S(> charged with solids that 

 it is ready to deposit them on the slightest disturbance. If, there- 

 fore, a little of the water of such concentrated urine is reabsorbed at 

 any point of the urinary passages the remainder is no longer able 

 to hold the solids in solution, and they are at once precipitated in 

 the solid form as gravel or commencing stone. In cattle, on the 

 other hand, which are kept at pasture in summer, or which are fed 

 liberally on roots, potatoes, pumpkins, apples, or ensilage in winter, 

 this concentrated condition of the urine is not induced, and under 

 such circumstances, therefore, the formation of stone is practically 

 unknown. Nothing more need be said to show the controlling influ- 

 ence of dry feeding in producing gravel and of a watery ration in 

 preventing it. Calculus in cattle is essentially a disease of winter 

 and of such cattle as are denied succulent feed and are confined to 

 dry fodder as their exclusive ration. "While there are exceptions, 

 they are so rare that they do not invalidate this general rule. It 

 is true that stone in the kidney or bladder is often found in the 

 summer or in animals feeding at the time on a more or less succu- 

 lent ration, yet such masses usually date back to a former period 

 when the animals were restricted to a dry ration. 



In this connection is should be noted that a great drain of water 

 from the system by any other channel than the kidneys predisposes 

 to the production of gravel or stone. In case of profuse diarrhea, 

 for example, or of excessive secretion of milk, there is a correspond- 

 ing diminution of the water of the blood, and as the whole quan- 

 tity of the blood is thus decreased and as the urine secreted is 

 largely influenced by the fullness of the blood vessels and the pres- 

 sure exerted uj^on their walls from within, it follows that with this 

 decrease of the mass of the blood and the lessening of its pressure 

 outward there will be a corresponding decrease of urine. The waste 

 of the tissues, however, goes on as before, and if the waste matter is 

 passed out through the kidneys it must be in a more concentrated 

 solution, and the more concentrated the urine the greater the danger 

 that the solids will be deposited as small crystals or calculi. 



Again, the concentrated condition of the urine which predisposes 



to such deposits is favored by the quantity of lime salts that may be 



present in the water drunk by the animal. Water that contains 20 



or 30 grains of carbonate or sulphate of lime to the gallon must con- 



33071°— 16 9 



