C 194 ] 
it, will work its Way out at. And thus this Diftem- 
per may be confider’d differently, as it happens to 
be in the different Stages of it. 
The Alteration which the Bone fuffers from the 
extravafated Matter lodged within the Subftance or 
Cavities of the Bone in the firft Stage of a Spina 
ventofa , becomes the Occafion of fome Exfoliation 
or Detachment from it. As that Matter acquires a 
greater Acrimony, the Texture of the Bone being 
relaxed, and the Lamella made foft and yielding, the 
Bone is enlarged in its Dimenfions; and, in the lad 
Stage of it, wherein the Bone is carious, the corro- 
live Matter deftroys the Continuity, as it makes its 
Way thro* the Cortex, and into the Joints. At this 
time Impoftumations appear in as many Places as the 
Matter can make its Way out at. The callous Mar 
ter lodged under the PerioJlinm y gradually oflifying, 
covers the Bone more or lefs with Exofiofesb and 
the Joints are ftiffned, by the Extravafation and In- 
duration of the Sap flowing out of the Bone there. 
The Impoftumations that happen in the Bone to* 
wards the Centre of long Bones, are always attended 
with additional Mifchief, as the working out of the 
Matter there meets with a greater Reftftance from 
their Lamella , which lie clofe, and are compact $ 
the Exfoliations made in the firft Stage, and, as it 
were, in the Beginning of the Spina ventofa there, 
being frequently confined and locked in by the Cor- 
tex of the Bone, or fome callous Expanfion on the 
Surface of it. In the laft Stage of this Diftemper in 
this Place, the Bone is ufually perforated with large 
Holes, tubulous Cavities, and fiftular Openings, and 
the main Bone rotten, at a time that the Exfoliations 
inclofed 
