22 A Manual of Veterinary Physiology. 



pound, and that the administration of inorganic compounds, 

 of lime in rickets is irrational and useless. 



Lime exists largely in clover and hay, but only in 

 small quantities in the cereal grains ; it is principally by 

 the hay that the amount excreted by horses through the 

 kidneys is supplied; it passes from the body in such 

 quantities that it cannot be held in solution by the alkaline 

 urine. In the body the calcium is in the form of phos- 

 phate, sulphate, and carbonate ; in the urine as carbonate 

 and oxalate. 



Magnesium salts occur in the body principally as phos- 

 phates, and in this form they enter largely into certain 

 foods, such as oats. The amount of magnesium passing 

 away from horses through the kidneys is small, but con- 

 siderable quantities derived from the food, and which 

 cannot be utilized in the body, pass out with the fasces ; by 

 collecting in the bowels this salt produces the ammonio- 

 magnesium phosphate calculi so common in horses. 



Phosphates are united with soda, potash, lime, and mag- 

 nesium. They are principally taken in with the food, 

 but may also be formed in the body from the metabolism 

 of phosphorus-containing compounds. The foods richest 

 in phosphoric acid are oil-cake and bran, whilst hay and 

 straw are poorest in this constituent. The combination of 

 phosphates with magnesium has just been alluded to. 

 Phosphoric acid is principally execreted by herbivora with 

 the faeces, only small quantities passing away with the 

 urine. 



Carbonates are found in several of the secretions of the 

 body, notably in the urine where they cause the most 

 intense evolution of gas on the addition of an acid. The 

 carbonates in the system of the herbivora result from the 

 combustion of the organic acids, malic, citric, tartaric, etc., 

 which enter the body as potassium salts, the potassium 

 being set free and uniting with carbonic acid to form 

 carbonate of potash ; the potassium also unites with sul- 

 phuric acid, for which see sulphur. 



The Sulphur in the body is derived from the albumin of 



