526 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



phosphate would immediately be precipitated in the blood. It has, however, 

 been conclusively shown that such salts when eaten produce an increase in the 

 calcium of the urine ' and it is known that blood has a special capability for 

 carrying calcium phosphate. Calcium carbonate and chloride are capable of 

 absorption, while absorption of the phosphate may be considered as still in 

 doubt. If calcium chloride be given, a little of the calcium appears in the 

 nine, and all of the chlorine, this being due to the conversion in the intes- 

 tine of calcium chloride into calcium carbonate and sodium chloride, which 

 latter is completely absorbed. Organic salts of calcium such as the acetate are 

 absorbable, as are probably proteid combinations with calcium such as casein. 

 Milk and egg-yolk are the foods richest in calcium salts, cow's milk containing 

 more calcium to the liter than does lime-water. 2 



The excretion of calcium takes place in major part as triple phosphate from 

 the wall of the small intestine, 8 in minor part through the urine (for the latter 

 see pp. 515 and 524). It is excreted during starvation, and is the principal 

 inorganic constituent of starvation feces (Yoit). The secretions of the intes- 

 tines, according to Fr. Miiller, 4 hardly contain enough calcium to account for 

 that found in the feces, so that it is probably excreted by the epithelial cells 

 of the villus. In starvation the source of excreted calcium is principally 

 from the breaking down of tissue, but partially from the metabolism of the 

 bones. The excretion is never large. On subcutaneous injection of small 

 amounts of calcium acetate in dogs, 5 the calcium excretion may be raised for 

 several days. On venous injection of 0.8 gram CaO as acetate, after one 

 hour but 0.3 gram could be found above the normal in the blood, and analy- 

 sis of the liver, kidney, spleen, and intestinal wall failed to reveal more than 

 the usual minimal amounts of calcium. As it is never rapidly excreted, it 

 must have been temporarily deposited in some unknown part of the body. 



Strontium, Sr = 87.5. 



Cremer 6 has shown, on adding strontium phosphate to almost calcium-free food of young 

 growing dogs, that the strontium line could he detected in the suhsequent spectral analysis 

 of their bones. Weiske, 7 on feeding young rabbits with food nearly free from calcium, 

 and with addition of strontium carbonate, found the ash in some of the bones to contain, 

 in the place of CaO, as high as 4.09 per cent, of SrO. In both of the above experiments 

 the skeleton remained very undeveloped in comparison with the normal, so that strontium 

 cannot be considered a physiological substitute for calcium. 



1 Riidel, Op. cil., S. 79. 



2 Bunge: I'liy.siologische Chemie, 3d ed., 1894, 8. 101. 



3 Voit F. : Zeitachriftfur Biologie, 1893, Bd. 29, S. 325. 



4 Zeitschrift fur Biologie, 1894, Bd. 20, S. 356. 



5 Rev : Archiv fiir exper, Pathologie unci Pfiarmakologie, 1895, Bd. 35, S. 298. 



r ' SUzungtiberichte der Gesellschaft fiir Morphologic unci Physiologie in M'dnchen, 1891, Bd. 7, 

 s. 124. 



7 Zcitxrhrift fiir Biologie, 1894, Bd. 31, S. 437. 



