CALCIUM PHOSPHATE AND CALCIUM CARBONATE. 30 1 



the homogeneous appearance due to the fusion of these discrete 

 particles into one mass. Pacchioni has also described the first ap- 

 pearance of lime salts in bone in the form of fine granules which 

 later form a homogeneous mass. 



The possible origin of these particles either by precipitation or 

 secretion will be discussed later. 



PART 3. DISCUSSION OF RESULTS. 



Concerning some of the physical phenomena of the precipitation 

 reactions studied, remarks have been made at appropriate places in 

 the previous pages describing the work and need not be repeated 

 here. 



There are a few points to be constantly borne in mind in con- 

 sidering the question of ossification, which have been very clearly 

 demonstrated by Wells. The most important is the fact that there 

 is a very definite and fixed ratio between the amount of calcium 

 carbonate and calcium phosphate deposited in bone. The second 

 point is that this same ratio is equally true in areas of calcification 

 in tissues other than bone. The third fact is that the processes of 

 ossification and of calcification are essentially the same, the kind of 

 matrix or tissue in which the deposit occurs differentiating the two 

 processes. 



Theories Regarding Deposition of Calcium Salt's. 



The reactions with calcium phosphate show it to be invariably 

 precipitated in a granular form so that if it were visible in bone 

 it should be evident in a finely divided amorphous form. As this 

 salt forms over eighty per cent, of the inorganic material, it ought 

 to be readily demonstrated, but this is not the case, because the 

 matrix is clear and homogeneous, not granular, except at the ad- 

 vancing edge of ossification in developing fcetal bones. 



It has been shown that in mixed solutions calcium carbonate is 

 not prevented, by the presence of the phosphate, from coming out 

 in typical spherules or crystals, so that it might be expected that 

 the carbonate would show in one of these forms in bone, in which 

 it forms fifteen per cent, of the salts. This expectation is further 

 strengthened by the fact that typical spherules have been found in 

 the shells of invertebrates, which are mostly calcium carbonate, by 



