26 



Ch. M. Lapiere 



one. These results are in agreement with the hypothesis that the collagen framework 

 of bone is synthesized as a non or slightly calcified matrix which undergoes progressive 

 changes related to aging and mineralization. 



On the basis of our knowledge of the organization of the collagen fibers in soft 

 connective tissues, these data allow us to propose a schematic representation of what 

 could be the relationship collagen — mineral — water in bone (Fig. 2). When 



N 



NM 



^ 



%. 



17 



1.9 



2.1 



Fig. 2. Schematic illustration of the organization of collagen fractionated from soft and calcified connective- 

 tissues. From left to right are represented the neutral isotonic salt extractable collagen (N) compared to the 

 least calcified 1.7 bone collagen, the neutral hypertonic salt extracted collagen (NM) from more compact fibers 

 and the 1.9 denser more calcified bone structures, the fibers extracted in acid medium (A) and the calcified 

 fibrous 2.1 element, finally, the bulk of the Insoluble fibers (I) and of the 2.2 most calcified bony structures 



collagen is synthesized in bone, It appears in the extracellular space as a very loose 

 arrangements of molecules comparable to the N fraction of soft connective tissue. 

 These loose fibers undergo immediate calcification as seen with the electron micro- 

 scope (S. F. Jackson, 1957). They may already have been present inside the osteoblast 

 according to Scott and Glimcher (1963). As they are loose fibers and slightly 

 calcified they contain a large amount of bound water and therefore have a light 

 density. As time passes after the formation of this new bone, the amount of water 

 decreases in the fibers while the deposition of calcium salt Increases. This process can 

 be compared to the maturation of the fibers In soft connective tissue. Their increased 

 organization requires a hypertonic medium for extraction (NM). This condensation 

 process has been demonstrated in vitro by Gross (1958 c). A further evolution of the 

 process of maturation and calcification of the newly formed element would lead to 



