310 THE SOLIDS. 



of bones was first observed by Drs. Todd and Bowman*, 

 who considered that it was concerned in the development of 

 blood-vessels. 



Presuming it to be proved that the bone cells are derived 

 from true corpuscles, we have yet to decide whether we are 

 to believe with Schwann f> that they are complete cells, and 

 that the canaliculi are prolongations of the walls of these 

 cells ; that, in fact, they possess a structure conformable with 

 that of the stellate pigment cells of the skin of the frog, or 

 of the lamina fusca of the eye ; whether we are to consider 

 with Gerber J, Bruns , and E. H. Mayer ||, that they are the 

 nuclei of primitive elementary cells and that the canaliculi are 

 prolongations of these ; whether, again, we are to regard them 

 with HenlelT as the cavities of cells, the walls of which have 

 become thickened, and the canaliculi of which proceed from 

 the central cavity through the thickened walls of the cells, as 

 do the porous canals of many vegetable cells ; lastly, whether 

 we are to believe, with Todd and Bowman, that the canaliculi 

 proceed from the nucleus, which afterwards becomes absorbed, 

 and that thus the lacuna is left. 



That the first view is the correct one, and that the bone 

 cells are to be regarded as complete corpuscles, the canaliculi 

 of which are formed by the extension of the cell wall, is, I 

 think, proved by watching the formation and development of 

 bone cells in growing spiculaB and by the action of dilute 

 hydrochloric acid, which, by removing the earthy matter, 

 allows the granular texture, which originally characterised 

 them, to be again seen. 



The last points left for consideration in reference to the 

 development of bone are, the modes of formation of the 

 medullary cavity, medullary cells, and Haversian canals. 



Formation of medullary Cavity. Traversing the sub- 

 stance of each cartilaginous epiphysis, a number of large and 



* Physiological Anatomy, Chap. 5. 



f Mikroskopische Untersuchungen, pp. 35. 115. 



| Allgemeine Anatomie, p. 104. 



Ibid. pp. 240. 252. 



|| Muller, Archiv. 1841, p. 210. ^[ Anat. Gen. t. vii, p. 409. 



