EXPLANATION OF THE PLATES. 



PLATE XXXY. 



DEVELOPMENT OF BONE. 



Fig. 1. A transverse section of the cartilaginous epiphysis 

 of the lower end of humerus, magnified 30 dia- 

 meters, showing the apertures of the canals by 

 which it is traversed. 



Fig. 2. The same in connection with the bone : in this figure 

 it will be observed that there are fewer canals, that 

 these are of larger calibre, and that the cartilage 

 cells are disposed around them in a radiate manner 

 in groups. 



Fig. 3. One of the apertures of the canal more highly mag- 

 nified, 330 diameters, showing more clearly the 

 arrangement of the cells around it, the contents of 

 the canal being granular corpuscles and blood- 

 vessels, as well as the fact that the intercellular 

 spaces nearest to the opening are the last to be- 

 come converted into bone : in most of the me- 

 dullary spaces of the second tier the granular 

 corpuscles have already made their appearance, the 

 cartilage cells having been removed by absorption. 



Fig. 4. The blood-vessels of the medullary cells of a young 

 bone near the epiphysis injected. For the speci- 

 men from which this figure was drawn I am in- 

 debted to the kindness of Mr. Quekett of the 

 Royal College of Surgeons. 



Fig. ,"). Transverse section of the shaft of a foetal long bone, 

 displaying the fact that in foetal bones there are no 

 llaversian canals, such entirely consisting of me- 

 dullary 



