[ 40 © ] 
to be reduced ; and thefe are the Perfections which 
have been hitherto required in this Machine. 
Commonly, when the Bone of the Arm is fuffici- 
ently ftretched and raifed, fo as to be on a Level with 
the Cavity of the Articulation, thofe Bones replace 
themfelves as it were -of themfelves, becaufe this 
Level is not always exa&; on the contrary, the Ex- 
tenfion and Counter-extenfion being never regular 
enough to hinder the Scapula , which is a moveable 
Part, from following a little the Head of the Bone, or 
its Extenfion, it happens almoft always, that this Head 
bears pretty ftrongly againft the Edge of the Cavity* 
and confequently does not fail to fall into the faid 
Cavity, as foon as it has only patted its Edge, and 
even before it has met the Level, or the Axis of the 
Hollow of the Articulation 5 but it is otherwise after 
an Extenfion, a Counter-extenfion, and an Elevation 
fo regular as thofe which may be performed by our 
Machine ; it may happen, that after the Three pre- 
ceding Operations, the Head of the Bone, without 
having touched the Edge of the Cavity, will be 
placed over-againft this Cavity, and upon a Level 
with its Axis, without being able to enter into it, by 
reafon of the Firmnefs and Exa&nefs of the Powers for 
retaining the oppofite Parts in this State of regular 
. Extenfion 5 and, in this Cafe, there will remain for 
you, in order to finilh the Operation, to condu& 
the Head of the Bone into its Cavity, or to let it go 
into it : But what will you do then > If you flacken 
the Extremity of the Lever, or if you lift the fame 
up, you will bring the Head back to the fame Place 
where you took it upj that is to fay, you will bring 
the Luxation to its former State. If you refolve to 
relax 
