PHOSPHATES OF MAGNESIA, SODA, AND POTASSA. 77 



of lactate of soda, the urine had an alkaline reaction. He also ob- 

 served that, if a solution of lactate of soda were injected into the 

 jugular vein of a dog, the urine became alkaline at the end of five, 

 or, at the latest, of twelve minutes. The conversion of these salts 

 into carbonates takes place, therefore, not in the intestine but in the 

 blood. The same observer 1 found that, in many persons living on 

 a mixed diet, the urine became alkaline in two or three hours after 

 swallowing ten grains of acetate of soda. These salts, therefore, 

 on being introduced into the animal body, are decomposed. Their 

 organic acid is destroyed and replaced by carbonic acid ; and they 

 are then discharged under the form of carbonates of soda and potassa. 



7. CARBONATE OF POTASSA. This substance occurs in very 

 nearly the same situations as the last. In the blood, however, it is 

 in smaller quantity. It is mostly produced, as above stated, by 

 the decomposition of the malate, tartrate, and citrate, in the same 

 manner as the carbonate of soda. Its function is also the same as 

 that of the soda salt, and it is discharged in the same manner from 

 the body. 



8. PHOSPHATES OF MAGNESIA, SODA, AND POTASSA. All these 

 substances exist universally in all the solids and fluids of the body, 

 but in very small quantity. The phosphates of soda and potassa 

 are easily dissolved in the animal fluids, owing to their ready solu- 

 bility in water. The phosphate of magnesia is held in solution in 

 the blood by the alkaline chlorides and phosphates ; in the urine, 

 by the acid phosphate of soda. 



A peculiar relation exists between the alkaline phosphates and 

 carbonates in different classes of animals. For while the fluids of 

 carnivorous animals contain a preponderance of the phosphates, 

 those of the herbivora contain a preponderance of the carbonates : 

 a peculiarity readily understood when we recollect that muscular 

 flesh and the animal tissues generally are comparatively abundant 

 in phosphates ; while vegetable substances abound in salts of the 

 organic acids, which give rise, as already described, by their decom- 

 position in the blood, to the alkaline carbonates. 



The proximate principles included in the above list resemble 

 each other not only in their inorganic origin, their crystallizability, 



1 Physiological Chemistry, vol. ii. p. 130. 



