28 



LECTURE II. 



some of the phenomena of osteogeny to surmise that the walls and the 

 nucleus of the cell were in opposite electric or magnetic states, one 

 attracting, the other repelling, the surrounding earthy particles. 



Certain of the columnar series of nucleated cells become more 

 aggregated or pressed together ; their nuclei become more concen- 

 trated, and, according to Miescher and Gerber, they coalesce and be- 

 come dissolved, leaving a cylindrical tube, parallel with the l9ng 

 axis of the future bone. First, a reddish lymph, and then a capillary 

 vessel is prolonged into each of these cylinders, which is converted 

 into a " Haversian," or vascular canal : before, however, the direct 

 influence of the circulation has penetrated so far, the nucleated carti- 

 laginous cells have arranged or propagated themselves in concentric 

 series round the cylinder, and the intervening layers of the mole- 

 cular blastema begin to be impregnated with the hardening salts, 

 which, being repelled by the nuclei of the cells, are forced into the 

 concentric laminated arrangement around the Haversian canal. The 

 establishment of the capillary circulation in these canals accelerates 

 the progress of ossification by the rapid import of new material : the 

 resisting nuclei of the surrounding concentric cells, pressed on all 

 sides, undergo a remarkable change, and the nucleolar matter is 

 forced out in rays, but chiefly in the direction where the resistance 

 is least, viz. towards the Haversian canal. The remaining central 

 nuclear matter and that of the divei'ging rays finally become dis- 

 solved, and establish permanent bone-cells and minute tubes, which 

 tubes, traversing the concentric lamella^, open into the Haversian 

 canal, and receive the transuded plasma from the blood- capillary. 

 The tubes branch and anastomose, and form the medium of the trans- 

 mission of the plasma through the densest osseous tissue. This sys- 

 tem of cells and tubes, in fact, perform the same important function 

 in the nutrition of the osseous tissue, which I ascribed in 1838 to 

 the corresponding cells and tubes of the cemental tissue of the teeth 

 of the Megatherium (vi. p. 104.) : and they might be appropriately 

 termed the " Plasmatic system." They correspond with one of the 

 series of the " vasa lymphatica" of the older physiologists ; the first 

 kind, for example, specified in Noquez's edition of Kiel, quoted by 

 Hunter : " Les premiers naissent des extremites arterielles ; on les 

 nomme ' arteres lymphatiques,' qui peut-etre ne sont autre chose que 

 les conduits excretoires d'une lymplie tres subtile, ou de la matic-re 

 qui transpire" (vii. vol. ii. p. 11.). The dentinal tubes of teeth and the 

 plasmatic tubes of bone are not, indeed, prolonged from attenuated 

 ends of arterial capillaries, but they receive the plasma transuded or 

 transpired from the parietal pores of the capillary system, and thus 



