448 CALCIFICATION, CONCRETIONS, AND INCRUSTATIONS 



bones remains constant, as also does the proportion of calcium and 

 phosphoric acid; if the decalcification occurred through solution by 

 lactic or other acids, he argued, the carbonate should be decomposed 

 first, ^^ whei'eas the lime salts seem to be taken out as molecules of 

 calcium carbonate-phosphate; i. e., in the same proportion as they 

 exist in the bone. On the other hand, it has been found in Pawlow's 

 laboratory that dogs kept for long periods after a pancreatic fistula 

 has been established, develop a condition resembling osteomalacia,^" 

 which would seem most reasonably explained as due to the constant 

 loss of alkali in the pancreatic juice. Furthermore, investigation 

 of Levy's objection to the acid solution theory has led to the observa- 

 tion that when mixtures of calcium carbonate and phosphate are in 

 colloids they are dissolved at equal rates. *^ Histologically, absorption 

 seems to depend largely upon a direct eating out of bone tissue, both 

 organic and inorganic substance, by osteoclasts (Cohnheim), followed 

 by a formation of an uncalcified osteoid tissue. (Senile osteoporosis 

 differs chiefly in that no new osteoid tissue is formed.) According to 

 Dibbelt^^ when osteomalacia is experimentally induced in pregnant 

 dogs and then recovery is allowed to take place, the decalcified bone 

 substance present in the active stage does not become calcified, but is 

 absorbed and replaced by new bone. 



Studies of metabolism in osteomalacia have shown a loss of calcium 

 by the body, especially in the urine, as shown by the following table 

 given by Goldthwait et al.:^^ 



McCrudden also found a considerable retention of nitrogen and 

 sulphur, which may be retained in the new-formed osteoid tissue; 

 magnesium^^ is also retained, probably being substituted for calcium 

 in the bones. It is known that when magnesium and strontium are 



^' Goto reports that in experimental HCl acidosis the bones lost 20 per cent, 

 of their CaCOa without appreciable loss of phosphate (Jour. Biol. Chenu, 1918 

 (36), .355). 



"> Babkin, Zeit. Stoflfwechsel, 1910 (11), 561; Looser, Vcrh. Deut. Patli. Gcsell., 

 1907 (11) 291. 



" Kranz and Liesegang, Deut. Monat. Zahnhcilk., 1914, p. 628. 



^2 Arbeit. Path. Inst. Tubingen, 1911 (7), 559. 



*' Goldthwait, Painter, Osgood and McCrudden, Amer. Jour. PhvsioL, 1905 

 (14), 389. 



** Corroborated by Cappezzuoli, Biochem. Zoit., 1909 (16), 355. 



