204 A Manual of Veterinary Physiology. 



sulphate is excreted it undergoes change in the presence 

 of the oxygen of the air, forming, amongst other bodies, 

 pyrocatechin, which gives the brown colour to stale urine. 

 The daily amount of ethereal sulphate compounds is 

 about I oz. 



Another sulphur compound of the urine is sulphocvanic 

 acid, found regularly in the urine of herbivora. The only 

 other substance of this class to which allusion will be made 

 is indoxylor indican, which is formed from indol, and yields 

 on oxidation indigo blue, which is commonly found in the 

 urine of the horse. 



The Colouring Matter of the Urine is urobilin, which is a 

 decomposition product of haemoglobin ; the change may 

 possibly take place in the liver, though it is generally 

 supposed to occur in the small intestine, through the bile 

 pigment being acted upon by the nascent hydrogen, the 

 product being absorbed and excreted by the kidneys. It is 

 generally considered that there is only the one urine pig- 

 ment ; it is certain, however, that in a diseased condition 

 other decomposition products of hemoglobin appear. 



The inorganic substances found in the urine are chlorine, 

 salts of calcium, magnesium, sodium, and potassium, phos- 

 phoric, sulphuric, and silicic acids. 



The nature and proportion of the salts vary with the 

 diet. Of the alkalies, potassium salts predominate in the 

 urine of the horse ; calcium salts are also largely repre- 

 sented. Meade Smith gives the following ash composition 

 of horse's urine : 



The quantities in this ash analysis do not agree with 

 my observations, but they convey the same truths, viz., the 



