KEl'KODUCTION OF BONK. 4G7 



is seen to be shooting, in thu manner peculiar to this mode of 

 regeneration, from a point corresponding to an ulcerated 

 portion of the old shaft. So striking is this peculiarity, that 

 it will at once recur to those who have had an opportunity of 

 observing new shafts in an early stage of formation ; as well 

 as the remarkable contrast between the smooth hard portions 

 of the dead or dying bone and the nodulated scales lying in 

 the separated periosteum, alternating with the former, and 

 concealing from direct view the rough or idcerated portions of 

 the dead shaft. In those instances in whicli the shaft has 

 died, with the exception of a ring or small portion at each or 

 one end, close to the epiphysis, the new bone shoots in 

 stalactitic masses in the longitudinal direction, their course, 

 direction, and magnitude, coiTcsponding to the forms of the 

 rings or portions of ulcerated bone in the old shaft. This is 

 an unfavourable form of necrosis, in consequence of the 

 difficulty encountered by the extremities of the new shell in 

 meeting in the centre, and the length of time required for the 

 process of regeneration. This form has also given rise to a 

 mistaken view of tlie source of the new bone in necrosis, u 

 belief that it is derived from the epiphysis. I have never seen 

 an instance in which the epiphysis supplied the new shaft, 

 and I have had occasion to point out that the specimens on 

 which such opinions were founded are in fact exemplifications 

 of the formation of the new, from a ring or portion of the old 

 shaft close to the epiphysis. An epiphysis is a distinct part, 

 ami has no greater tendency to supply the losses of the 

 principal mass of the bone to which it belongs than the femur, 

 fibula, or astragalus, to supply the loss of a tibia. 



Another remarkable peculiarity, arising from the circum- 

 stance of the new bone invariably shooting from spots 

 corresponding to ulcerated portions of the dead shaft, is met 

 with in instances where one side of a dead shaft is not 

 ulcerated, and the other side, or a portion of it, has undergone 



