68 THE GROWTH OF BONE 



the epiphyses was damaged ; from this end the new 

 bony development was slenderer than from the un- 

 injured end. 



In another experiment, two and a half inches of 

 bone with its periosteum were removed from the 

 radius of a young dog, and metal caps fitted over 

 the sawn extremities of the shaft remaining in situ. 

 Seven weeks later, the gap was found completely 

 bridged by bone, and the two metal caps had come 

 together. Owing to bending of the ulna, they did 

 not absolutely meet, but passed one another laterally. 



In yet another case, the plate of cartilage between 

 the shaft and epiphysis was removed from the radius 

 of a young dog. The bone failed to grow at that end, 

 and a lateral expansion of the epiphysis became 

 attached to the ulna and stunted its growth also. 

 This experiment is of course paralleled in man, 

 when a separation of an epiphysis takes place, or 

 when the growing end is removed in the excision of 

 a joint. 



Increase in the girth of bone has been attributed to 

 the periosteum. Between it and the bone, osteoblasts 

 are to be found in young animals, and these lay down 

 ring after ring of concentric lamellae. If the develop- 

 ing animal is fed with pigment, such as madder, for a 

 short period, there may be found months later a 

 buried pigmented ring of bone which was laid down 

 at that time. Another classical experiment we owe to 

 Duhamel (1739), who buried a silver ring under the 

 periosteum of a young animal, and found some time 

 after that the ring had become covered by subsequent 

 bone formation. 



