52 INORGANIC PROXIMATE PRINCIPLES. 



The alkaline carbonates are partly introduced as such with the food, 

 but are to a great extent formed within the body by the decomposition 

 of other salts contained in the substance of certain fruits and vegetables. 

 Various of these fruits and vegetables, such as apples, cherries, grapes, 

 potatoes, carrots, and the like, contain malates, tartrates, and citrates 

 of the alkaline bases. It has, furthermore, been often observed that 

 after the use of acescent fruits and vegetables containing the above salts, 

 the urine becomes alkaline in reaction from the presence of the alkaline 

 carbonates. Lehmann 1 found, by experiments upon his own person, 

 that within thirteen minutes after taking 15.5 grammes of sodium lactate, 

 the urine had an alkaline reaction. He also observed that, if a solution 

 of this substance 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 found that, in 

 many persons living on a mixed diet, the urine became alkaline in two 

 or three hours after swallowing 0.65 gramme of sodium acetate. 



The organic acid in these cases is decomposed and oxidized with the 

 production of carbonic acid and water ; and the original salts are thus 

 replaced by the alkaline carbonates, which appear in the urine and tem- 

 porarily modify its reaction in the manner above described. 



A preponderance of vegetable food, accordingly, influences the quan- 

 tity of the alkaline carbonates in the system, and consequently the reac- 

 tion of the excretions. As a rule, the urine of man and of the carnivo- 

 rous animals is clear and acid, while that of the herbivora is alkaline 

 and turbid with calcareous deposits. This turbid and alkaline urine 

 will often effervesce with acids, showing the presence of carbonates in 

 considerable quantity. Bernard has shown that this difference depends 

 upon the alimentation of the animal, and that although in carnivorous 

 and herbivorous animals under ordinary conditions the urine is respec- 

 tively acid and alkaline, if they be both deprived of food for a few days 

 the urine becomes acid in both, since they are then, in each instance, 

 living upon their own tissues. Furthermore, a rabbit, whose urine is 

 turbid and alkaline while feeding on fresh vegetables, if kept upon a diet 

 of animal food, soon produces an excretion which is clear and acid. The 

 reverse effect is produced upon a dog by changing his food from meat 

 to vegetable matters. Finally, it is also shown 2 that the urine of the 

 young calf while living on the milk of the mother is clear and acid ; but 

 after the animal has been weaned and feeds upon vegetable matter, its 

 urine becomes alkaline and turbid, like that of the adult animal. 



9. Sodium and Potassium Sulphates, S0 4 Na 2 and S0 4 K 2 . 

 The sulphates are also to be regarded as constant ingredients of the 

 body, as they are found in several of the animal fluids, including the 



1 Physiological Chemistry. Cavendish edition. London, 1851, vol. i. p. 97. 



2 Milne Edwards, Legons sur la Physiologie. Paris, 1862, tome vii. p. 471. 



