The Urine. 205 



heavy proportion of potassium salts, the small proportion 

 of sodium salts, the excess of lime salts, the small proportion 

 or absence of phosphoric acid, the large proportion of 

 sulphuric acid, and the small amount of magnesia. 



There is a considerable variability in the ash analysis, 

 which, no doubt, is largely due to the difference existing in 

 foods. It has been found that in ruminants the calcium 

 salts are mostly excreted with the feces, whereas in the 

 horse the bulk passes through the kidneys ; in the same 

 way it is said that sheep excrete nearly all the potassium 

 of the food by the kidneys, whilst the horse only excretes 

 rather more than half by this channel. It is certain that 

 phosphoric acid, which forms such a prominent feature in 

 the urine of carnivora and omnivora, is in the horse almost 

 wholly excreted by the intestines. 



Calcium.— More lime exists in the urine than is soluble 

 in an alkaline fluid, so that we have both suspended and 

 dissolved lime, the former increasing with the age of the 

 urine owing to the development of ammonia, until pre- 

 sently the whole of the lime is precipitated. The lime 

 exists in combination with oxalic, carbonic, hippuric, and 

 sulphuric acids. The whole of these combinations do not 

 necessarily exist in one specimen of urine ; the salts formed 

 depend upon the amount of lime and the affinity it possesses 

 for the unsaturated acids. I cannot find that the amount 

 of lime in the food influences the production through the 

 kidneys, but I have found more lime in the urine of horses 

 at work than of those at rest. Oxidate of lime crystals are 

 common microscopic deposits in the urine of the horse ; the 

 oxalic acid is probably in part derived from the food. 



Magnesium in the urine is also suspended and dissolved, 

 the amount which is suspended being increased by that 

 thrown down by the ammonia generated as the urine gets 

 older. 



Potassium exists largely in the urine, derived from the 

 potash of the food ; it forms numerous combinations, the 

 one with carbonic acid being the cause of the fixed alka- 

 linity of the urine. There is more potash found in the 



