308 JAMES CRAWFORD WATT. 



9. In the rapidly developing foetal skeleton the first appearance 

 of bone in the matrix is in the form of fine granules or globules 

 which quickly fuse or coalesce to form a homogeneous mass. This 

 might be interpreted according to the bias of the observer as sup- 

 porting evidence either of precipitation or of secretion of the salts 

 into the matrix. 



10. The view advanced by Barille and supported by Wells's 

 work, that calcium is carried in the blood as tribasic calcium car- 

 bonophosphate, is probably correct, as it furnishes the bone salts 

 in the proper proportion, but their view of its deposit in the matrix 

 as a precipitate due to change in concentration of carbon dioxide 

 does not appear correct in view of the fact that no precipitate of 

 the bone salts is visible. 



11. The theory that the salts furnished by the blood are taken 

 by the bone cells and secreted by them along with the matrix seems 

 reasonable in view of the condition found in the matrix. 



12. The action of the osteoblasts seems to be reversible, they 

 being able to absorb or take up the calcium salts again out of the 

 matrix. 



In concluding this paper I wish to acknowledge my indebtedness 

 to others by thanking Professor J. Playfair McMurrich for special 

 apparatus and for valuable references, also the following for pro- 

 viding material for investigation : Professor W. H. Piersol, Dr. 

 R. D. Defries, Dr. Banting, Dr. Simpson, Dr. Dafoe, and Dr. Low. 



BIBLIOGRAPHY. 

 Barill6, A. 



'04 De Taction de l'acide carbonique sous pression sur les phosphates metal- 

 liques; combinaison (carbonophosphates) ou dissolution, applications 

 diverses. Journ. de Pharm. et de Chimie, Ser. 6, T. 19, p. 14, 71, 196, 

 245, 295. 



'10 Role des constituants de la dissociation de la carbonophosphate trical- 

 cique dans la genese du tissu osseux et des diverses concretions a 

 base de phosphate et de carbonate de calcium. Journ. de Pharm. et 

 de Chimie, Ser. 7, T. i, p. 342. 

 Bast, T. H. 



'21 Studies on the Structure and Multiplication of Bone Cells facilitated 

 by a new Technique. Amer. Jour, of Anat., Vol. 29, pp. i39-i57> 



