296 Ovservations upon the 
tion of parts which have served their destined 
purpose, and the deposition of earthy matter 
so as to assimilate the new formed parts to the 
original bone ; this requires a period far be- 
yond that when the limb becomes useful, for 
the tumour at the point of fracture does not 
arrive at its greatest diminution for a great 
length of time; the absorbent vessels of the 
part would seem to retain for ever afterwards — 
an aptitude to be easily excited into action, 
since under circumstances of long continued 
fatigue, privation, and disease, at any suc- 
ceeding: period of life, they will take up the 
parts thus formed and leave an ununited bone, 
as was the case in some instances of the crew 
of the Centurion under Lord Anson. 
These observations were made by fractur- 
ing the thigh bone of young rabbits; the 
fracture constantly overwrapped, no attempt 
being made at reduction, hence I was enabled 
to’ attend to what was going on upon the 
face of the fracture much better than if the 
bone had been replaced. 
It has been thought that the callous tumour 
was a coagulable juice flowing from the face 
of the fracture, and gradually hardening into 
bone. It has been asserted that the effused 
blood itself underwent changes from which 
this tumour resulted. One observer attri- 
