NEW FORM OF SECTION - CUTTING MACHINE. 273 



track, and the fruitless jerking, bending, and quivering of the saw- 

 blade, as the teeth bit too deep, and rendered it necessary to dis- 

 lodge them before any further progress could be made. 



Tlien, again, think of the clumsy contrivances rendered necessary 

 in consequence of this vicious custom, the strong backs necessary 

 for tendon and surgical saws, some of these jBtted with joints so 

 that the operation of sawing may not be stopped when the back 

 reaches the edge of the sawslit. Think also of the torture of 

 sawing in the dissecting-room (both to the person who saws and to 

 the person who looks on), of the dangerous wounds caused, the 

 sweating, the jerking, and locking of the sawblade ; of the bent 

 blade and broken saw-teeth that inevitably result from this bad 

 principle ; and you may then be able to conceive how much trouble 

 may be avoided by simply reversing the position and action of the 

 saw-teeth. In this matter the Arabs are far ahead of us. When 

 in Arabia I noticed a native workman using a saw like an old 

 barrel-hoop in a most efficient manner on some rather ticklish 

 timber. On looking at it minutely I observed the reversed 

 direction of the teeth, and at once perceived the value of the 

 arrangement. 



It must be evident to you all that power can be better applied in 

 drawing back than pushing from one ; hence it is that beginners 

 generally get over any difficulty by sawing as they withdraw, thus 

 breaking off or blunting the saw-teeth. Again, with the teeth 

 reversed, no back is needed to the saw, for should the teeth bite 

 too deep the greater the strain applied the more tensely straight 

 the blade is held. 



Moreover, an unskilled arm can use more precision in drawing 

 back than in pushing forward, and thus this method of using a 

 saw will be found to be superior in every way, to the present 

 method ; and I hope soon to see it supersede it, more especially in 

 Surgery and Anatomy. In my dissecting-rooms in Edinburgh all 

 my pupils used, with the greatest facility and precision, an unbacked 

 saw thus prepared, without a single wound having been received, 

 and the saw itself was in as good a condition at the end as it was 

 at the beginning of the session. 



I think it unnecessary to apologise to you for this apparent 

 digression, the point being of the greatest importance in the 

 working of the saw in my machine ; for without this explanation 

 the utility and advantage of thus using the saw might have 



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