FRANCIS H. McCRUDDEN 



physiological action of the magnesium and calcium ions does not come 

 into consideration here. We merely have a partial substitution of mag- 

 nesium phosphate for calcium phosphate as a structural material. 



Such a substitution has been experimentally reproduced. 



Koenig fed three sets of young rabbits food poor in calcium 

 phosphate. Then to the diet of one set calcium phosphate was added ; to 

 the diet of a second set, magnesium phosphate; and to the diet of the 

 third set, strontium phosphate. The rabbits which were given magnesium 

 phosphate were found to have twice as great an absolute amount of mag- 

 nesium in the bones as the others. In the case of the rabbits fed strontium 

 phosphate, an element foreign to the body, the amount of calcium in the 

 bones was decidedly decreased, and about five per cent strontium found 

 instead. Table 13 shows the figures obtained in these experiments. 



TABLE 13 



EFFECT OF CALCIUM, MAGNESIUM, AND STRONTIUM CONTENT OF THE DIET ON BONE 



COMPOSITION 



The earlier experiments of Weiske(&), in which he used adult animals, 

 gave negative results; but later experiments (c), in which he used young 

 animals, gave results similar to those of Koenig. 



Table 14 shows Weiske's figures. 



TABLE 14 



EFFECT OF CALCIUM, MAGNESIUM, AND STRONTIUM CONTENT OF THE DIET ON BONE 



COMPOSITION 



More recent studies of Weiser show this same replacement of calcium 

 by magnesium on a diet poor in calcium, but containing an abundance 

 of magnesium (Weiser(a)). 



