662 PHILOSOPHICAL TRANSACTIONS. [aNNO 1742-3. 



room not only for the foot, or for the point it rests on, which may meet there, 

 but also for a part of the lever, called its spur, which always moves towards 

 that notch when the lever is lowered. The figures and the use of the machine 

 will show the necessity of this construction much better than any description. 

 From the bodice come out 2 broad straps, of the strongest leather, with their 

 buckles. One of those straps is to go about the back of the chair, and round 

 the body of the patient : the other goes over the shoulder, very near the arti- 

 culation, and keeps the scapula and the clavicula in their situation against the 

 efforts of the lever. 



That part of the machine, which may properly be called the ambe, is com- 

 posed, like that of Hippocrates, of 2 pieces ; one vertical, which he called the 

 foot of the ambe; and the other horizontal, which forms the lever. It is 

 chiefly in these 2 pieces that this ambe differs from that of Hippocrates. 



The foot is a piece made either of wood, pi. l6. fig. 2, or of iron, fig. 3. 

 Its upper extremity is split into a sort of mortise, which receives the spur or 

 tenant t of the lever ab, fig. 8. It is pierced by several holes, which answer 

 to as many others on the spur. Below this mortise the foot becomes more 

 slender and cylindrical ; by this part it enters into a round hole in the arm of 

 the chair ; this slender part of the foot is pierced by several holes, in order to 

 run an iron pin through, which lies flat on the arm of the chair, and keeps the 

 foot raised to a height proper for the person that undergoes the operation. For 

 the greater security, 2 pins may be run through; one which rests on the arm of 

 the chair, and the other on the seat itself, through which the foot also passes. 

 The iron foot, fig. 3, may be provided with a sort of large ring c, under the 

 pin, which will render its rotation the easier. If an iron foot should be pre- 

 ferred, the hole for it in the arm of the chair must be made narrower, either by 

 filling up the old one with an iron box or clout, which may be taken away, if a 

 wooden foot be used ; or we may even at first fit those holes for the iron foot, 

 setting the wooden one quite aside. 



The lever abhd, fig. 3, pi. 15, is the most compound piece of all, and also 

 the most important. It is made of a real lever ab, and of a piece fitted to it 

 DG. The lever properly so called, ab, is made round on its inferior surface ; 

 the upper surface is fiat; and all along on the middle of it there runs a rod, 

 forked at the end, which fits to a groove of the same figure in the inferior surface 

 of the sliding-piece fg, fig. Q, pi. l6. This lever diminishes towards the extre- 

 mity a, where the moving power is to be applied ; the other extremity, b, is 

 somewhat rounded off at the end, the better to insinuate itself under the arm- 

 pit. On this larger extremity is a kind of spur or tenant, t, the upper part of 

 which is joined to the lever by 2 iron pins ; so that, on taking out the pins, the 



