664 rHlLOSOPHICAL TRANSACTIONS. [aNNO 1742-3. 



more conveniently the head and the neck of the humerus, and to preserve the 

 soft parts from any contusion, which the impulse of the machine might pro- 

 duce, by its greatest forces acting on that part. 



The arm being thus placed, and well stretched out on the bracer, you tie 

 about it 1 sliding knots, one above the elbow, and the other over the wrist, 

 after having guarded those parts with a very thick and soft compress ; the 2 

 sliding knots are fastened to the fork of the elastic tail of the bracer ; after 

 which you complete the fixing of the arm with the 3 girths of the bracer, under 

 which are also put compresses like those just mentioned. 



The arm being thus well adjusted, you endeavour to give to the body, and 

 to the hollow of the articulation of the luxated bone, the proper situation and 

 steadiness necessary for the success of the operation, which is easily executed 

 with this machine, by the girths of the bodice, of which the horizontal one 

 keeps the patient's breast closely applied against this piece, and the vertical 

 girth retains the scapula, the clavicula, in short, all the parts where the bone 

 is to be pushed back, in a situation proper for receiving it, and for not deviat- 

 ing by yielding to the efforts of the machine. 



Every thing being thus disposed, the surgeon places himself behind the pa- 

 tient, mounted on something that raises him high enough to inspect the effects 

 of the process ; to examine by the touch where it operates : in short, to con- 

 duct the whole both by feeling and by the eye. The surgeon being placed, 

 the assistant who is to conduct the extremity of the lever, works it according 

 to his directions, but exceedingly slow, that the extensions may be made with 

 less pain, and more effectually. 



When the luxation is below, it is sufficient for its reduction to lower the ex- 

 tremity of the lever, as is done with the ambe of Hippocrates. But here ap- 

 pears a great difference between the working or playing of these 2 sorts of 

 levers. The ambe of Hippocrates is a plain lever ab, fig. 7, pi. l6, the motion of 

 which is from a to a, and consequently has for its extension only the space ca, 

 when it is brought to its last term of becoming perpendicular, ab, while it has 

 all AC, or ia, for its elevation. The ambe of Hippocrates therefore only raises 

 the bone of the arm, without scarcely stretching it ; and this is the defect 

 which M. Petit, with reason, blames it for ; and which is still more sensible, 

 if we take the action of the lever in d, the point whereabouts it must meet the 

 edge of the cavity, and may cause those mischiefs that are apprehended from 

 it; but instead of placing the fixed point of that lever in 1, lower it to 2, by 

 means of the tenant 1 2 ; then the direction of the end of the lever becomes 

 VE : its elevation is but ih ; and the extension it produces is ae, or de : if you 

 lower still the lever's point of rest, as in 3, by a longer spur, the elevation of 



