HE OSSEOls SYSTEM. 



365 



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to it. In a cylindrical bone of this kind consequently, the 

 i n tire portion formed from cartilage, presents the figure of a 

 double cone with rounded bases; 

 and that formed from the periosteal 

 layers, 1, 2, '6, 4, P 3 , and l 1 , 2 l , S\ 

 4\ P 3 , the form of an elongated 

 tube thickest in the middle, and re- 

 sembling an elongated vertebra of a 

 Pish, with conically hollowed, termi- 

 nal surfaces. The articular cartilage 

 C, is the unossified portion of the 

 epiphysal cartilage, and the medul- 

 lary cavity which is not shown in 

 the figure (it may be supposed to 

 be indicated pretty nearby by the 

 outlines of the fourth bone E 3 E 3 ), 

 is formed by the resorption of the 

 entire osseous substance derived 

 from the cartilage and periosteum 

 of the younger bones; — in this 

 case the first three, E E, E 1 E 1 , 

 and E 2 E 2 . 



In the cylindrical bones, with- 

 out a medullary cavity, and in all 

 other bones containing nothing 

 but spongy substance in the in- 

 terior, the absorption does not pro- 

 ceed to nearly the same extent 

 as it does in the above-described 

 cases, that is to sav, onlv to the 

 production of a looser spongy substance in the interior, and, 

 consequently, we find, for instance in the vertebne, more or 





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Fig. 134. Diagram of the growth of a cylindrical hone. B, primary rudiment 

 the diaphysis ossified and the epiphyses cartilaginous : A, the same bone in four 

 stages of further advance, E'PPE', E-P'P'E 2 , E 3 P 2 P 5 E 3 , E 4 P 3 P 3 E 4 ; PP'P S P 3 , peri- 

 osteal layers of these four bones ; the space contained within 1, 2, 3, 4, and 1'. 2', 

 3 ', 4', indicates the portion which in the largest bones is formed from cartilage; 

 E'E 1 , cartilaginous epiphyses of the second bone; E 2 E 2 , epiphyses of the third bone, 

 in one of which is an osseous nucleus; E 3 E 3 , E 4 E', epiphyses of the fourth and fifth 

 bones, all with larger epiphysal nuclei : G, articular cartilage ; /, K, interstitial car- 

 tilage between the ossified epiphysis and diaphysis. 



