78 



MACROMOLECULAR COMPLEXES 



It should be clearlv kept in mind that what we have been dis- 

 cussing is the phvsicochemical basis of the induction of mineiahza- 

 tion. The minerahzation of the endoskeleton of vertebrates and the 

 exoskeleton of certain invertebrates is a vital process which demands 

 exquisite homeostatic control mechanisms which are highly specific 

 in their operation. As in so many other cases in the organism where 



NATIVE TISSUES 



I 



Fig. 13. Diagrammatic illustration of the possible role of certain components 

 of the ground substance (long threadlike material surrounding the collagen 

 fibrils) in helping to inhibit calcification in normally unmineralized tissues. The 

 "?" indicates that it is not yet certain whether depolymerization (represented 

 by the short segments surrounding the fibrils) is itself effective, or whether 

 depolymerization and subsequent removal from the tissue are necessary. (From 

 Glimcher, 1958.) 



control and specificity must be of the highest order, in both nor- 

 mally mineralized and normallv unmineralized tissues a number of 

 highly specific regulating mechanisms obviously must exist. There 

 is every reason to expect that mineralization in both kinds of tissues 

 is imder the control of many delicately balanced regulatory factors, 

 providing the organismic and cellular regulation of the mechanism 

 which initiates the formation of the inorganic crystals and which 

 controls their further growth. 



