Callous Tumour. 297 
butes its formation entirely to the internal 
membrane, another entirely to the external 
membrane; another to a thickening of the 
periosteum alone, and others to the bone it- 
self. In this conflict of opinion the subject 
still remains very much undecided, and upon 
the origin and formation of the callous tu- 
mour, all authors 1 have consulted are ob- 
scure. I hope sufficient has been said to shew 
that this tumour consists of two successive 
effusions ; the primary one from the internal 
membrane, smoothing the face of the frac- 
ture by the removal of its asperities, thereby 
preventing further injury to the soft parts, 
and offering a fit medium for the reciprocal 
communication. of the vessels of the injured 
parts: the secondary effusion from the exter- 
nal membrane aided by the injured soft parts, 
and forming the great mass of the tumour, 
a deficiency of either of which is attended 
by its peculiar inconveniences and mischiefs, 
and incompatible with an early and perfect 
recovery. 
VOL, It. Pp 
