82 THYSIOLOGY OF FARM ANIMALS [CH. 



is always present in the virine of the horse and many other 

 Herbivora. It may be made to yield indigo. 



Mucus. The urine of the horse is generally more or less 

 mucinous, the amount of mucus depending upon diet, the 

 occurrence of oestrus, etc. On a diet of oats without hay the 

 quantity may be considerable. Mucus in small amounts is 

 often present in the iirine of other animals. 



Pigments. The chief colouring matter of urine is urochrome, 

 an oxidation product (on exposure to air) of urobilin which is a 

 derivative of bile-pigment. 



Salts. These are derived partly from the salts of the food, 

 but to a greater extent are metabolic products of the tissues. 

 They are alwaj^s present in considerable quantity, but vary in 

 kind according to diet and according to the species of animal. 



Gases. The gases in virine only occur in insignificant quantities. 



Ammonia. Urine always contains a small quantity of 

 ammonia since blood containing this substance traverses the 

 kidney before reaching the liver where it is converted into urea. 



Pathological constituents of urine. Protein is present in 

 human urine in cases of Bright's disease (albuminuria) and in 

 certain other pathological conditions, especially when pus is 

 formed through bacterial action. Protein occurs in horse's 

 urine in cases of inflammation of the lungs and pleura. In cases 

 of glycosuria where the tissues are unable to utilise the sugar 

 in the blood glucose overflows into the urine. Such a condition 

 may be produced experimentally by removing the pancreas 

 (see p. 141), by puncturing the floor of the fourth ventricle of 

 the brain, or by injecting adrenaline, phloridzin and certain 

 other drugs. In lactating animals lactose may occur in the 

 urine. Sugar is rarely or never present in horse's urine. Bile 

 occurs in urine in cases of jaundice, rendering the fluid a dark 

 brown colour. Blood appears in the urine when haemorrhage 

 in any of the urinary passages takes place. Further, a blood 

 pigment (methaemoglobin) is found in cases of haemoglobinuria, 

 which is due to a disintegration of corpuscles in the circulating 

 blood. In cattle with 'black water fever' (a disease of Tropical 

 Africa) this pigment may also occur in urine associated with 

 oxyhaemoglobin. Amino-acids, such as tyrosine, are occasionally 

 found in urine after a disintegration of protein tissue (as in atrophy 

 of the liver) . 



