Vl] THE EXCRETORY ORGANS 83 



The urine of the horse has normally a spccilic gravity of about 

 1036 (that of man being about 1020). In colour horses' urine 

 is yellowish-brown, rapidly becoming brown on standing. It is 

 alwaj^s turbid (owing to suspended calcium and magnesium 

 carbonates). Its odour is due to aromatic substances. Indican 

 and hippuric acid are well-marked constituents, the latter taking 

 the place of xiric acid. Phosphates are absent or only present in 

 small amounts. The quantity secreted depends upon the season, 

 the diet, and the amount of work done. On a nitrogenous diet 

 the amount of water in the tirine is greater ; on a diet of oats and 

 no hay the mucinous substances are more numerous and may be 

 so much so that the urine has the consistency of egg albumin. 

 In winter owing to the effect of cold on the skin the quantity of 

 urine is greater than in summer. For a similar kind of reason 

 horses at work secrete less than horses at rest. The urine of 

 mares during oestrus may have the consistenc\' of oil. 



The urine of the ox has a specific gravity of about 1015, being 

 less than that of the horse owing to the greater amount of water 

 secreted. The nitrogenous content consists chiefly of urea and 

 hippuric acid but there is less of the latter than in the horse. 

 Straw of cereals produces a large amount of hippuric acid, and 

 when this is so the amount of urea is correspondingly less. Calves 

 while sucking jield a urine in which phosphates and uric acid 

 are abundant, such animals resembling Carnivora. 



The urine of the sheep has a specific gravity of about 1010. 

 Hippuric acid is abundant, being produced especially by a diet 

 of new meadow hay. 



The urine of the pig has a specific gravity of about 1015. Its 

 composition varies with the diet, pigs being comparatively 

 speaking omnivorous. Uric and hippuric acids are both important 

 constituents, and there is also much urea. 



The urine of the dog has a specific gravity of about 1030, but 

 it varies within wide limits. Uric acid is present typically, but 

 is absent on a herbivorous diet. On a normal flesh diet the 

 reaction is very acid (owing to acid sodium phosphate resulting 

 from oxidation of the phosphorus of proteins in the meat). 

 Indican is usually present. 



