UROGENITAL SYSTEM 221 



food taken. In meat-eaters 98 per cent, of the proteid in the 

 food is absorbed ; in man living on a mixed diet 2^-6 per cent 

 of proteid and 1-3 per cent, of carbohydrates (vegetables and 

 bread) are rejected in the faeces, almost the whole of the re- 

 mainder being assimilated. 



VI. Urogenital System, 

 i. Urinary Organs. 



We have already seen in the chapters on anatomy that in 

 man and the majority of mammals the urinary organs consist 

 of a pair of symmetrically placed, bean-shaped kidneys, each 

 with a ureter opening into the bladder. In the urine are ex- 

 creted water and inorganic substances, together with certain 

 effete nitrogenous compounds. 



The amount of urine passed in twenty-four hours is shown 

 in the following table : 



Adult man . . . 1,500-1,700 c.cm. 

 Horse .... 3-S-io litres 



Ox .... 6-10-25 ,, 



Sheep and goat . . O' 3-0*9 



Pig .... 1-5-8-0 



Dog (large) . . 0-3-1-3 



Cat .... 0-2-0-3 



Human urine has certain specific characteristics. It is 

 faintly acid in reaction, has a salt, bitter taste, and an odour 

 like bouillon. The specific gravity averages 1015, the tempera- 

 ture when passed 39 C. ; its organic constituents are urea, uric 

 acid, creatin, hippuric acid, xanthin, hypoxanthin, urinary pig- 

 ments, phenol and indigo sulphates The inorganic constituents 

 are sodium and potassium chlorides, ammonium sulphate, acid 

 potassium phosphate, calcium and magnesium phosphates, am- 

 monium salts, iron and CO 2 . 



The urine of carnivora (dogs) is strongly acid, has an odour 

 of garlic, and brown in colour ; its specific gravity varies from 

 1025 to 1055; it contains a large amount of urea, rather less 

 uric and hippuric acids, is rich in sulphates and poor in chlorides. 

 The urine of herbivora is alkaline, is muddy yellow in colour, 

 and has a most unpleasant only faintly aromatic (benzoic acid) 



