CALCIUM PHOSPHATE AND CALCIUM CARBONATE. 305 



First, Schafer and Pacchioni have described the first appearance 

 of bone salts in developing bone in the form of minute granules 

 which quickly coalesce. This I have confirmed. This evidence 

 could also be interpreted as showing the presence of the salts to be 

 due to secretory activity. Secondly, Olivier in a tumor of the 

 breast and Pettit in a tumor of the maxilla and also in a renal cyst 

 saw and made illustrations of calcospherites. These bodies can be 

 explained only as a precipitation phenomena, but they do not afford 

 sufficient evidence to prove that this is the process whereby the 

 bone salts are deposited. And so these salts, after reaching the 

 bone in correct proportions as the double salt above mentioned, 

 must be deposited in the matrix by some more subtle process than 

 ordinary precipitation. 



Here we have recourse to the secretion theory. The bone salts 

 in their proper proportions having been brought to the cell by the 

 blood, are taken by the cell and secreted as an integral part of the 

 matrix in combination with the ossein, the organic base, which it 

 is generally admitted already, is a product of the cells. This will 

 produce a matrix uniform in appearance, with salts invisible, and 

 provides the proper proportion of each salt, as the cell is in its turn 

 provided with the two salts in that exact amount. Histological 

 evidence shows that the fibrous matrix appears first in the newly 

 forming bone and impregnation with the bone salts begins immedi- 

 ately, the salts showing as fine granules at first, and coalescing as 

 their quantity increases, to form a homogeneous matrix. 



Reversibility of Calcium Reaction. 

 There seems to be evidence that this process of secretion is 

 reversible, the bone cells being able to take up the calcium salts 

 again. Wells and others have shown that calcium is removed from 

 the bones in cases where there is a great demand for it in the body, 

 as in pregnancy, or where it is being steadily lost by the body, for 

 instance by way of a pancreatic fistula. Also, the osteoclasts re- 

 sponsible for the normal resorption of bone are supposed by some 

 authors to be only osteoblasts which have changed their function. 

 And further, where a graft of either living or dead bone, or a bone 

 plate and bone screws are used to repair an injury, a process known 



