SODIUM AND POTASSIUM PHOSPHATES. 49 



Notwithstanding various surmises which have been presented from 

 time to time with regard to its possible decomposition and the re-com- 

 bination of its elements in the body, we have no certain knowledge of 

 such changes taking place in the sodium chloride while forming a con- 

 stituent of the animal frame. It passes from the alimentary canal to 

 the blood, from the blood to the tissues, and is finally discharged with 

 the urine, mucus, and cutaneous perspiration, in solution in the water 

 of these fluids. Under ordinary circumstances, by far the largest pro- 

 portion passes out by the kidneys. The quantity of sodium chloride 

 thus discharged with the excretions by an adult man is about 15 

 grammes per day j 1 of which 13 grammes are contained in the urine, and 

 2 grammes in the perspiration. Thus, of all the sodium chloride con- 

 tained in the body, considerably more than ten per cent, passes through 

 the system in twenty-four hours. This fact plainly indicates the activity 

 and importance of this salt in the daily internal changes of nutrition. 



6, Potassium Chloride, KC1. 



This substance is found in very many if not all of the animal tissues 

 and fluids, accompanying the sodium chloride, many of the properties 

 of which it shares, and with which it is closely related in its physiological 

 characters. It is especially abundant, as compared with the sodium 

 chloride, in the muscles and in the milk, less so in the blood, the gastric 

 juice, the urine, and the perspiration. Both salts are neutral in reaction, 

 and are retained in the liquid form in the blood and secretions by solution 

 in the water of these fluids. The potassium chloride is introduced as 

 an ingredient of both animal and vegetable food, and is discharged with 

 the mucus, the urine, and the perspiration. 



7. Sodium and Potassium Phosphates, Na 2 HP0 4 and K 2 HP0 4 . 



These substances, associated under the name of the alkaline phos- 

 phates, are of the greatest importance as ingredients of the animal body. 

 They exist universally in all its solids and fluids, and in the latter are 

 present in the liquid form by means of their ready solubility in water. 

 No doubt they are useful in a variety of ways, but at least one of their 

 most important characters is their property of exhibiting an alkaline 

 reaction. This reaction is essential to a large number of the vital pro- 

 cesses taking place in the interior, and is present, without exception, in 

 all the animal fluids which are actually contained in the circulatory 

 system, or in the closed cavities of the body. An acid reaction, on the 

 other hand, is found only in a very few of the organic fluids which are 

 either employed in the process of digestion or are discharged externally. 



The following list shows the comparative frequency of alkaline and 

 acid reactions in the animal fluids : 



1 Neubauer und Vogel-, Analyse des Hams, Wiesbaden, 1872, p. 54. Beneke, 

 Pathologic des Stoffwechsels, Berlin, 1874, p. 322. 



