DISINTEGRATION AND REMOVAL OF BONE. 159 



of obtaining sufl&ciently thin sections for examination 

 by very high powers. Such sections are absolutely 

 necessary for demonstrating the changes which occur 

 here on a scale very small compared with that upon 

 which they proceed in the cartilage of the frog. 



218. The disintegration and remoTal of bone. — 

 The removal of the osseous tissue is effected upou the 

 same principle as the removal of fatty matter, § 194, 

 and other substances which have to be gradually dis- 

 solved and taken up by the blood as soluble sub- 

 stances, instead of being cast off and carried away as 

 particles of considerable size like the old cells of cuticle 

 or of a mucous membrane. No one would, however, 

 have been led to expect that the hard matter of bone 

 would have been easily dissolved away and appro- 

 priated by living bioplasm; for bone is not easily 

 dissolved, and when subjected to the action of ordi- 

 nary fluids undergoes very little change. Small 

 pieces of bone have been subjected to the action of 

 serum and pus for long periods of time without any 

 appreciable change being induced. Nevertheless, it 

 has been distinctly demonstrated that the hardest 

 tissues like the fang of the temporary tooth, may be 

 dissolved away, and removed during life. It is re- 

 markable that the material concerned in the process 

 of removal should be a soft and moist semi-fluid 

 substance which comes into very close contact with 

 the bone and dentine. By employing the carmine- 

 solution as I have described, § 68, the actual par- 

 ticles engaged in the removal of these hard tissues 

 have been demonstrated very distinctly, and in bone 

 tissue at different periods of age. They are little 

 particles of bioplasm which, as they grow and mul- 

 tiply, take up the formed material that was produced, 

 it may have been, by their predecessors. In the same 

 way it has been shown that the bioplasm of mildew 

 may grow and live upon the formed material it has 

 already produced, § 9-i. The bone tissue diappears 



