6o 



ELEMENTS OF HISTOLOGY. [Chap. vn. 



origin. At the extremity of the 

 <3eT 



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Fig. 36. From a Longitudinal Section of 

 Femur of Rabbit, through the part in 

 which the intermediary cartilage joins 

 the end of the shaft. 



a. Intermediary cartilage; 6, zone of calcified 

 cartilage; c, zone, in which the calcified 

 trabeculae of cartilaee become gradually in- 

 vested in osseous substance, shaded light in 

 the figure; the spaces between t lie traboculse 

 contain marrow, and the capillary blood- 

 vessels are seen here to end in loo'ps ; rf, in 

 this zone there is more bone formed : the 

 greater amount the farther away from this 

 zone. (Atlas.) 



as the periosteum reaches, e.g., to 

 articular cartilage. 



shaft, however, the 

 spongy bone is all 

 endochondral bone, 

 and it continues to 

 grow into the inter- 

 mediate cartilage as 

 stated above, so long 

 as the bone grows as 

 a whole (Fig. 36). 

 Of course the parts 

 of this spongy bone 

 nearest to the centre 

 of the shaft are the 

 oldest, and ulti- 

 mately disappear by 

 absorption into the 

 central medullary 

 cavity. In the epi- 

 physis the spongy 

 bone is also endo- 

 chondral bone, and 

 its formation is con- 

 nected with the deep 

 layer of the articu- 

 lar cartilage. 



Underneath the 

 periosteum and on 

 the surface of the 

 spongy endochon- 

 dral bone at the 

 extremity of the 

 shaft, the periosteal 

 bone is represented 

 only by a thin layer, 

 extending as far 

 the margin of the 



