450 PHYSIOLOGICAL CHEMISTRY. 



debted to Liebig for showing that the mineral substances are just 

 as necessary for the normal composition of the tissues and organs, 

 and for the normal course of the processes of life, as the organic 

 constituents of the body. The importance of the mineral constit- 

 uents is evident from the fact that there is no animal tissue or 

 animal fluid which does not contain mineral substance, and also 

 from the fact that certain tissues or elements of tissues contain 

 habitually certain mineral substances and not others, which ex- 

 plains the unequal division of the potassium and sodium compounds 

 in the tissues and fluids. With the exception of the skeleton, which 

 contains about 220 p. m. mineral bodies (VoLKMANtf), the animal 

 fluids or tissues are poor in inorganic constituents, and the quan- 

 tity of such only amounts, as a rule, to about 10 p. m. Of the total 

 quantity of mineral substances in the organism, the greatest part 

 occurs in the skeleton, 830 p. m., and the next greatest in the mus- 

 cles, about 100 p. m. (VoLKMAtftf). 



The mineral bodies seem to be partly dissolved in the fluids and 

 partly combined with organic substances. In accordance with this 

 the organism persistently retains, with food poor in salts, a part of 

 the mineral substances, also such as are soluble, as the chlorides. 

 On the burning of the organic substances the mineral bodies com- 

 bined therewith are set free and are eliminated. It is also ad- 

 mitted that they in part combine with the new products of the 

 burning, and also that they in part are attached to organic nutri- 

 tive bodies absorbed from the intestinal canal which are poor in 

 salts, or nearly salt-free, and are thus retained (VoiT, FORSTER). 



If this statement be correct, it is possible that a constant supply 

 of mineral substances with the food is not absolutely necessary, and 

 that the amount of inorganic bodies which must be administered 

 is insignificant. The question whether this be so or not has not, 

 especially in man, been sufficiently investigated ; but generally we 

 consider the need of mineral substances by man as very small. It 

 may, however, be assumed that man usually takes with his food a 

 ^considerable excess of mineral substances. 



Investigations on animals in regard to the action of an insufficient 

 supply of mineral substances with the food have been made by sev- 

 eral investigators, especially FORSTER. He observed, on experiment- 

 ing on dogs and pigeons, with food as poor as possible in mineral sub- 



