334 A MANUAL OF VETERINARY PHYSIOLOGY 



develops an acid urine, and it is certain that if hay be withheld 

 from the diet, the urine of the horse may be rendered acid by 

 feeding entirely on oats. This is said to be due to hippuric acid 

 in rye-grass feeding. In the case of oats it is probably due to the 

 formation of acid phosphates from the food, due to the absence 

 of vegetable organic acids in the oats. 



In the dog the urine is acid, due to the acid phosphate of soda, 

 and not to any free acid ; no free acids exist in the urine of any 

 animal. In the pig the reaction is either acid or alkaline, depend- 

 ing on the diet : an animal diet producing an acid and a vegetable 

 diet an alkaline urine. The acidity of the urine may be increased 

 by the use of mineral acids, as we have seen in speaking of 

 ammonia (p. 329). The alkalinity of the urine is increased on 

 standing, especially in summer weather. 



The amount of water secreted with the urine differs consider- 

 ably in the various classes of animals. It is generally considered 

 in the horse that of the total intake of water not more than 

 one-third leaves the body by the kidneys. The writer obtained 

 as the mean of many observations, 4-8 litres (8J pints) of urine 

 in twenty-four hours. This agrees with the observations of 

 Munk,* who regarded 3 to 4 litres as the mean excretion in the 

 horse. In the ox a larger amount of urine is passed — 6 or 10 to 

 25 litres (10, 17, 44 pints) daily. Sheep, 0-3 to 0-9 litre (J pint to 

 1 J pints). Pigs, 1*5 to 8 litres (2-6 to 14 pints). Dogs, 0-5 to 1 litre 

 (o-8 pint to i-6 pints). Tereg,f who gives this table, states that 

 the excretion of water by the kidneys and other channels in the 

 various classes of animals is as follows : 



Herbivora : 20 per cent, excreted by the urine ; 80 per cent, by 



lungs, skin, and bowels. 

 Omnivora : 60 per cent, excreted by the urine ; 40 per cent. 



by lungs, kidneys, and bowels. 

 Carnivora : 85 per cent, excreted by the urine ; 15 per cent. 



by lungs, skin, and bowels. 



Food rich in nitrogen causes a greater secretion of urine. 



Urine of the Horse. 



Specific Gravity. — This varies within wide limits dependently 

 on the diet and the amount of dilution. The mean of a large 

 number of observations was 1036, the highest registered was 

 1050 and the lowest 1014. 



The Quantity of urine is liable to very considerable variation, 

 depending on the season and the diet ; the more nitrogen the 

 food contains the larger the amount of water consumed, and the 

 greater the bulk of urine excreted. The mean of a large number 

 of observations was 4-8 litres (8J pints) in twenty-four hours, 



* Quoted by McKendrick. f Ellenberger, op. cit. 



