44 PHYSIOLOGICAL CHEMISTRY. 



vegetable food, and is discharged with the mucus, the urine, and the 

 perspiration. 



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



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

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

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

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

 no doubt useful in a variety of ways, but one of their most important 

 characters is their alkaline reaction. This reaction is essential to a 

 large number of the vital processes, and is present in all the animal 

 fluids contained in the circulatory system, or in the closed cavities of 

 the body. An acid reaction, on the other hand, belongs to but few of 

 the animal fluids. One of these is a secretion employed in the digestive 

 process ; the rest are all discharged externally. 



The following list shows the comparative frequency of alkaline and 

 acid fluids in the human body : 



FLUIDS WITH AN ALKALINE REACTION. FLUIDS WITH AN ACID REACTION. 



1. Blood-plasma. 1. Gastric juice. 



2. Lymph. 2. Perspiration. 



3. Aqueous humor. 3. Mucus of the vagioa. 



4. Cephalo-rachidian fluid. 4. Urine. 



5. Pericardial fluid. 



6. Synovia. 



7. Fluids of the living muscular 



tissue. 



'8. Mucus in general. 

 9. Milk. 



10. Spermatic fluid. 



11. Tears. 



12. Saliva. 



13. Bile. 



14. Pancreatic juice. 



15. Intestinal juice. 



If we take into account the carbonic acid exhaled with the breath, it 

 is evident that an alkaline condition is in general characteristic of the 

 internal fluids, while the products of excretion present an acid reaction. 



Of the internal fluids the most essential is the plasma of the blood, 

 since it supplies the materials of nutrition to the entire system ; and its 

 reaction has been found invariably alkaline, not only in man, but also 

 in every species of animal in which it has been examined. This reac- 

 tion is necessary to life, since Bernard demonstrated that an injection 

 of dilute acetic or lactic acid into the veins of a living animal produces 

 death even before the point of neutralization has been reached. 



The alkaline reaction of the blood-plasma gives to this fluid its 

 capacity for dissolving carbonic acid. According to Liebig, water 

 which holds in solution one per cent, of sodium phosphate can absorb 



