INORGANIC ELEMENTS. 21 



tively high sulphur content. Of the exact manner in which 

 the sulphur is combined in most of these bodies but little is 

 known. 



Bases. The several acid radicals referred to occur in com- 

 bination with metals and four of these only are present in 

 the body in appreciable quantity. These are calcium, mag- 

 nesium, sodium and potassium, and they exist in the form of 

 salts with the acid radicals. To these four the iron of the 

 blood must be added, but it is present in organic combina- 

 tion. In a following chapter it will be shown to what extent 

 these bases are present in ordinary foodstuffs. Of some it is 

 important that they enter the body in certain forms only, 

 otherwise their utilization assimilation is imperfect or even 

 impossible. This is especially true of the iron, the chief use 

 of which is in the building up of hemoglobin. For this pur- 

 pose the iron of the ordinary mineral salts is not available, but 

 it may be taken from certain peculiar organic combinations. 

 Many mineral matters are as essential for the growth of the 

 body as are the organic foods to be described in the next chap- 

 ters and care must be observed to provide them in sufficient 

 quantity, especially in the feeding of the young. There is 

 some reason for believing that most of the basic material 

 assimilated in the body is in the form of complex salts or 

 organo-metallic combinations of some kind. The sulphur, 

 phosphorus and carbon are so found and possibly the metals 

 also. It has been pointed out that in the oxidation of such 

 organo-metallic compounds carbonates or basic salts must 

 result, and some portion at least of these salts must be avail- 

 able to combine with the sulphuric acid arising from the 

 oxidation of the protein substances. According to Bunge 

 common salt is the only mineral substance, in excess of that 

 furnished by the usual organic foods, which the body actually 

 demands in large amount. 



