558 VETERINARY PHYSIOLOGY 



In herbivora, when suckling or when fasting, the urine is 

 acid, but when on their normal diet it is alkaline. 



The alkalinity is due to the presence of alkaline carbonates 

 formed from the citrates, malates, and tartrates of the vegetable 

 foods, and also from the acetates, etc., produced by the decom- 

 position of cellulose in the rumen and intestine. 



Urine in carnivora is normally transparent; but when it 

 has stood for a few hours, a cloud of a mucin-like substance is 

 seen floating in it. In herbivora, as the urine cools, it rapidly 

 becomes turbid and throws down a white precipitate composed 

 cbieHy of carbonate of lime. 



The smell of urine is characteristic, and it may be modified 

 by the ingestion of many different substances. 



III. Composition. 



The tests for the various constituents of the urine must be 

 studied practically {Chemical Physiology). 



Since the relative amounts of water and solids vary Avithin 

 such wide limits, the percentage amount of the later is of little 

 moment. Under average conditions, the water constitutes 

 about 96 per cent., and the solids about 4 per cent. Of these 

 solids, rather more than half is organic, rather less than half 

 is inorganic. Since water and solids are derived from the 

 water and solids taken by the animal, the amounts excreted 

 depend upon the amounts taken, and must be considered in 

 connection with them. Thus, if a horse takes little fluid, it will 

 pass little water in the urine. If it takes little food, a small 

 quantity of solids will be excreted by the kidneys. 



Since excretion and ingestion must be studied in relation- 

 ship to one another, it is convenient to compare them during a 

 definite period of time, and the natural division into days of 

 twenty-four hours is generally adopted. 



Under ordinary conditions, the amount of solid food taken 

 per day does not vary very greatly, but the amount of fluid 

 imbibed varies within much wider limits. For this reason, 

 Avhile the amount of water excreted in the urine per diem varies 

 enormously, the amount of solids is more fixed. 



In the horse, on an average diet, about 5 to 8 litres- of water 



