1 6 HUMAN PHYSIOLOGY 



muscles iof c The amount of ash in each tissue varies much 

 with age and nourishment. The ash percentage of tissues is 

 as follows : 



Skeleton 22.0$ Heart \.\% 



Muscle 

 Liver. 



Spleen.. . 

 Lungs. . . 

 Intestine. 



Pancreas i.< 



Brain and spinal cord. 1. 



Blood 0. 



Kidneys 0. 



Skin o. 



The ash contains (with the exception of iron oxide) only 

 neutral salts, derived from the bases potassium, sodium, 

 calcium, magesium, and from carbonic, sulphuric, phosphoric, 

 and hydrochloric acids. More than 80$ are phosphates 

 (chiefly calcium phosphate); the "next largest in quantity are 

 the chlorides (sodium chloride) ; then follow the carbonates 

 and, last of all, the sulphates. 



The salts of potassium and sodium, found in ash, are 

 soluble in water, while the carbonate and phosphate of 

 calcium and magnesium, iron oxide and iron phosphate are 

 insoluble in water. In the body fluid the carbonate and 

 phosphate of calcium and magnesium are acid and therefore 

 soluble in water. The carbonates of the alkalies are also 

 present in the body as acid salts (sodium bicarbonate). 



When two or more salts of different bases or acids are dissolved 

 in water, they exchange their components reciprocally, in such a 

 manner that each base is united with each acid. In the body 

 fluid there are four bases and four acids; according to this theory, 

 sixteen salts ought to be formed. Moreover, the dibasic sulphuric 

 acid and carbonic acid form two salts with each base, while the 

 tribasic phosphoric acid forms three salts (the primary, secondary, 

 and tertiary salts). According to the theory, therefore, many 

 more salts must be formed. The quantity of each salt formed 

 depends, however, upon the chemical affinity and upon the abso- 

 lute quantity of the components entering into the reaction (law 

 of mass action). Hence, many of the salts formed according to 

 the theory may be present only in traces, and the number of salts 

 to be considered is much reduced. In reviewing the salts of our 

 body, an uncertainty always remains, so that the existence of 

 many salts is not absolutely proved. 



