OSSIFUATION. 337 



of the edifice proceeds. The way is cleared at first 

 by the absorption of the central part of the carti- 

 lage, and a few particles of ossific matter are depo- 

 sited in its room. While this process is going on, 

 greater activity is displayed in the arteries ; they 

 rapidly enlarge in diameter, so as to admit the 

 colouring globules of the blood ; and they thus 

 become visible to the eye, which can now follow 

 their course without difficulty. From being at 

 first red points, they soon spread out into lines, of 

 which we trace the branches to a certain extent, 

 although we cannot pursue them to their minuter 

 ramifications. They now assume more active func- 

 tions, and hasten to execute their task by depositing 

 granules of calcareous phosphate : these are laid 

 down, particle by particle, in a certain determinate 

 order, and in regular lines, so as to form con- 

 tinuous fibres. When a great number of these 

 delicate fibres are gathered together and connected 

 by other fibres, which shoot in various directions 

 across them, a texture composed of an assemblage 

 of long spicula and thin plates, is constituted. 



In the cylindrical bones, the spicula prevail, 

 and they are arranged longitudinally, and parallel 

 to one another, and to the axis of the bone. They 

 first constitute a ring in the middle of its length : 

 this ring enlarges in all its dimensions, but prin- 

 cipally in its length ; the spicula becoming larger, 

 not by the stretching of their parts, in consequence 

 of the insinuation of fresh materials between those 

 already deposited, but by the addition of new par- 

 ticles at both their extremities. In like manner, 

 the ring increases in thickness, not by the depo- 

 sition of phosphate of lime between the original 



VOL. I. z 



