RICKETS AND CARIES. 163 



ment of bone, in the removal of old Haversian 

 systems, and in the formation of new ones> in the 

 union of fractured ends of bones, in caries, and in 

 the formation of bone cancer, the bioplasts or masses 

 of living germinal matter are the active agents. If 

 bone is to be absorbed these little masses of bioplasm 

 multiply very rapidly, and increase at the expense of 

 the surrounding bone. On the other hand, if bone is 

 io be formed, it has been shown that the masses of bio- 

 plasm having increased in number for a time, cease to 

 multiply. Each increases in size, and the outer part 

 slowly undergoes conversion into formed material, 

 which in its turn becomes gradually impregnated 

 with hard calcareous salts. The harder the bone is 

 to be, the slower must this process proceed. Now in 

 inflammation of bone the bioplasts of the lacunae 

 increase in size, and appropriate the formed material 

 adjacent to them. Thus, a lacuna becomes much en- 

 larged, and is found to contain several small spherical 

 masses of bioplasm instead of one. The bone tissue 

 between several lacunae may be disintegrated and re- 

 moved, and thus a space of considerable extent may 

 be scooped out even in the compact tissue, and may 

 be occupied by masses of bioplasm, resulting from the 

 division of the bioplasts belonging to several lacunae. 

 This is one way in which an abscess in bone may 

 originate. 



223. Rickets and caries. In these conditions the 

 vital changes going on in osseous tissue are much 

 more active than healthy bone, which lives and grows 

 but slowly in comparison. The morbid processes are 

 characterised by the increase of bioplasm, which 

 grows too fast for the condensation of the tissue 

 which is requisite for the production of true bone to 

 take place. Here, as in all other oases, rapid change 

 is associated with brief duration. The well developed 

 normal lasting bone tissue is formed very slowly, and 



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