78 PHYSIOLOGY OF FARM ANIMALS [CH. 



to some extent in animals, micturition (like defaecation) may be 

 a voluntary act, that is to say, it is possible to inhibit the reflex 

 which would otherwise occur. 



A horse during micturition stands with its hind-legs extended, 

 its fore-legs generally adv^anced, and its tail raised upwards. 

 After micturition the mare erects the clitoris, but why this should 

 happen is not obvious. Horses as a rule can only micturate 

 when standing upright. They cannot do so while lying down, 

 or while at work or trotting, but an oestrous mare can discharge 

 urine while cantering. In the ox micturition can occur while 

 walking. The cow raises her back and brings her hind limbs 

 forward, at the same time lifting her tail. 



The following are the daily amovints of urine discharged in 

 man and the domestic animals under normal conditions : 



Man 1-5 litres 



Horse 5 to 8 litres 



Ox 10 to 25 ., 



Sheep 1 to 5 ,, 



Pig 1-5 to 8 „ 



Dog -5 to 3 „ 



It will be seen that the amounts given for any one species show 

 a wide range of variation. This is due partly to differences in 

 the size of the animal, but to a greater extent to the influence 

 of temperature variation and the factors referred to above. 



Composition of Urine. Normal urine may contain the follow- 

 ing substances : 



(1) Water. 



(2) Nitrogenous end products (urea, uric acid, hippuric acid, 



creatine, creatinine). 



(3) Aromatic compounds (benzoic acid, ethereal sulphates 



of indol, etc.). 



(4) Mucus. 



(5) Coloviring matter. 



(6) Inorganic salts (chlorides, sulphates and phosphates of 



sodium, potassium, calcium and magnesium). 



(7) Gases (chiefly carbon dioxide, and traces of nitrogen and 



oxygen). 



(8) Ammonia. 



We may now consider these separately and then pass on to 

 deal with certain features of special interest in the urine of the 

 different domestic animals. 



