DISEASES OF THE URINAKY ORGANS. 131 



small particles (gravel), or have concreted into large masses (stone, 

 calculus). In cattle it is no uncommon thing to find them distending 

 the practically microscopic tubes in the red substance of the kidney, 

 having been deposited from the urine in the solid form almost as soon 

 as that liquid has been separated from the blood. These stones ap- 

 pear as white objects on the red ground fonned by cutting sections of 

 the kidney, and are essentially products of the dry feed of winter, and 

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

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

 cows. Little water being introduced into the body with the food, and 

 a considerable amount being expelled with the breath and perspira- 

 tion 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 food, it becomes so charged with solids that it 

 is ready to deposit them on the slightest disturbance. If, therefore, 

 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 concen- 

 trated condition of the urine is not induced, and under such circiun- 

 stances, therefore, the formation of stone is practically unknown. 

 Nothing more need be said to show the controlling influence 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 food 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 succulent ration, yet such masses usually 

 date back to a former period when the animal was restricted to a dry 

 ration. 



In this connection it 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 Avhole amount of 

 the blood is thus decreased, and as the quantity of urine secreted is 

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

 sure exerted upon 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 



