124 DIURETICS 



MEDICINES ACTING ON THE URINARY ORGANS 

 ON THE KIDNEYS : DIURETICS 



Diuretics are agents which cause increased secretion of 

 urine. 



The amount of urine is liable to much variation, depending 

 mainly on the nature of the food, the quantity of water 

 drunk, and the proportion of fluid removed by the bowels 

 and skin. Horses during the twenty-four hours pass from 

 two quarts to two gallons, or on an average about ten 

 pints. Secretion is augmented during digestion, especially 

 when the diet is rich in proteids, by such food as heated 

 oats or musty hay, and by vetches, particularly when animals 

 are unused to them. More urine is passed during rest than 

 when the horse at active work is losing fluid freely by the 

 skin and lungs. Major-General Smith, from a series of 

 examinations of the urine of horses, finds the specific gravity 

 averages 1036, and that 3| ounces of urea are excreted in 

 the twenty-four hours. Cattle pass 10 to 40 pints of urine 

 per diem, the specific gravity ranging from 1007 to 1030. 

 Sheep pass 10 to 30 ounces of alkaline urine having a specific 

 gravity of 1006 to 1015. Pigs excrete 3 to 14 pints of urine, 

 which may be acid or alkaline. The quantity of urine, 15 to 

 35 ounces, excreted by the dog depends upon the diet and 

 the size of the animal. The specific gravity ranges from 

 1016 to 1060. 



The urinary secretion is increased by a variety of con- 

 ditions, notably by raising the pressure of blood in the 

 Malpighian tufts ; by cardiac stimulation, especially in 

 cases where there is valvular disease and consequent venous 

 congestion of the kidney ; also by contraction of the blood- 

 vessels of other vascular areas, as when cold diminishes 

 cutaneous activity. Then too, any condition which in- 

 creases the percentage of water in the blood (hydraemia), 

 such as saline infusions, causes diuresis. Irritation of the 

 medulla in the floor of the fourth ventricle experimentally 

 produced by mechanical injury, or naturally produced by 

 circulation of venous blood, greatly increases secretion, 



