4G8 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



that process. In siicli instances, the new bone proceeds from 

 points corresponding to the ulcerations, and shoots in the 

 form of arches across the smooth portion of the okl bone, 

 meeting from either side, and giving rise to new processes 

 which ultimately enclose the whole. In instances of this sort 

 regeneration is effected with difficulty, and there is a tendency 

 in the old shaft to ulcerate out on the side on which it has 

 supplied no osseous centres of regeneration. 



The death of the entire shaft of a long bone must be a 

 very rare occurrence. In a case of this kind, the shaft would 

 be found lying loose in a cavity formed by the epiphysis at 

 each end, and the separated periosteum on the sides. The 

 bone itself, although its surface might be opened up by in- 

 flammation, wordd present no ulceration or actual deficiency 

 of substance. In a case of this kind, I believe no regeneration 

 whatever would take place. The epiphyses have no tendency 

 to assist ; and the periosteum has separated without a single 

 portion of the shaft from which new bone might be produced. 



In the majority of instances of what is incorrectly named 

 death of the entire shaft, ulcerated portions or deficiencies of the 

 surface will be met with ; and in the periosteal sheath, scales 

 of new bone corresponding to these will be perceived. I have 

 observed the process by which these ulcerations are produced, 

 and have already described it in the chapter on ulceration. 



The first appreciable inflammatory changes in bone occur 

 within the Haversian canals. These passages dilate or become 

 opened up, as may be seen on the surface of an inflamed bone, 

 or better in a section. The lesult of this enlargement of the 

 canals is the conversion of the contiguous canals into one 

 cavity, and the consequent removal or absorption of all the 

 osseous texture of the part. This removal of the substance 

 of the walls of the Haversian canals is not to be explained by 

 pressure arising from effused lymph, understood either in a 

 mechanical sense, which is inapplicable to actions of this 



