CHAP. V.] 



OSSIFICATION. 



117 



Scapula of a foetus at the seventh month ; shew- 

 ing the progress of ossification. Natural size. 

 The light parts are epiphyses as yet cartilaginous 

 From the Museum of King's College, London. 



a great measure to that in which 

 it is designed that the chief 

 strength of the structure may lie. 

 Thus, in the bones composing the 

 vault of the cranium, there is al- 

 ways a very decided radiation from 

 the most prominent part of the 

 convexity of each. In the scapula 

 this direction is indicated by the 

 lines of shading in the accompany- 

 ing figure. The outline marks 

 the limits of the temporary carti- 

 lage, in which no other points of bone have yet appeared. 



The minute history of the F!f J- 30 - 



process by which temporary 

 cartilage is converted into 

 bone, is of extreme interest, a 

 Very good descriptions of it 

 have been given by Sharpey, 

 Miescher, and others ; from 

 which, however, it will be 

 seen by the following ac- 

 count that we differ in some 

 important particulars. 



The nucleated cells of tem- 

 porary cartilage are small, 

 and pretty uniformly scat- 

 tered through a sparing, 

 homogenous intercellular 

 substance. The nuclei are 

 granular, and large com- 

 pared with the cells, which 

 are distinguished from the 

 surrounding substance 



Fig. 30. Vertical section of cartilage C 

 near the surface of ossification : a. Ordi- 

 nary appearance of the temporary carti- 

 a'. Portion of the same more highly 

 mamiified. 6. The cells beginning to 

 :c the linear direction. 6'. Portion 

 more magnified. Opposite c, the ossifica- 

 tion is extending i,, the intercellular spaces, 

 and the rows of cells are seen resting in the 

 cavities so formed ; the nuclei being more 

 ted than above, c'. Portion of the 

 same more highly magnified. From a new- 

 born rabbit which had been preserved in 

 spirit. 



'*' 



