104 BOXE. 



Fig. 62. 





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Fig. 62. — Highly magnified Transverse Section op Superficial Part op Femur — 

 Human Fcetus (Klein). 

 a, h, c, iieriosteiim ; c, internal layer, with numerous osteoblasts, passing in to form 

 d, new bony growth, which is covered with osteoblasts, some of which are imbedded iu it, 

 forming bone corpuscles. Numerous Mood-vessels are seen cut across, in the periosteal 

 ingrowth, some filled with blood-coi-puscles, others empty. 



the bone increases in length by the ossification continuing to extend 

 into the intervening cartilage, which goes on growing at the same 

 time ; and it appears that in the part of the shaft already ossified 

 little or no elongation takes place by interstitial growth. This 

 is shown by an experiment first made by Hales and afterwards by 

 Dnhamel and by John Hunter, in which, two or more holes being bored 

 in the growing bone of a young animal at a certain measured distance 

 from each other, they are found after a time not to be farther asunder, 

 although the bone has in the mean while considerably increased in 

 length.* In like manner the shaft also increases in circumference by 

 deposition of new bone on its external surface, while at the same time 

 its medullary canal is enlarged by absorption from within. A ring of 



* Hales, Yeget. Statics., 4th edit. p. 340 ; Duhamel, Mem. dc I'Acad. des Sc. 174-3 et 

 seq. Hunter (rejjorted by Home) iu Trans, of Soc. for Imp. of Med. and Chir. Know- 

 ledge, vol. ii. ; also Catalogue of Hunterian ]\Iuseum, vol. i., ix 249. Duhamel was led 

 from some of his exiieriments to infer that an interstitial elongation took place near the 

 ends ; but there is some doul)t left as to the precise circumstances of the experiments in 

 these cases. Ijoth Hales and Duhamel, in experimenting on the gi'owing tibia of a chicken, 



