252 OBSERVATIONS 



the thigh-bone, this improvement of Cheselden is more ef- 

 fential than in the amputation of the humerus, where the 

 flefhy fibres, though oblique, are proportionally longer, and of 

 courfe their retraction greater. 



Where the fibres of mufcles run obliquely,- it is evident, 

 and has been obferved by Borellus and others, that the fi- 

 bres will be more numerous than if the fame fpace had been 

 covered with longitudinal fibres \ and although an oblique fi- 

 bre will not raife a weight with the fame force as a ftraight 

 fibre, yet the number of the fibres may be fo much increafed 

 by their obliquity, as to do more than compenfate for the lofs 

 of force occafioned by the obliquity. Thus, let us fuppofe a 

 longitudinal mufcle to be five inches long, and one inch in 

 breadth, and let us fuppofe it to contain in its breadth four fi- 

 bres or ropes, each one-fourth of an inch in diameter, as in 

 T. 2. fig. i. the force of this mufcle may be reprefented by the' 

 number 4. 



Let us next fuppofe thefe ropes to be cut into pieces, each of 

 which is one inch and a quarter in length, as reprefented by 

 dotted tranfverfe lines A, B, C, we (hall, by doing fo, form 16 

 ropes or fibres. 



Let us next fuppofe, that thefe ropes, reprefenting mufcular 

 fibres, are laid obliquely, like the hypotenufes of right-angled 

 triangles, of which the bafes are equal to one inch, and the 

 height or perpendicular equal to three quarters of an inch, as 

 in T. 2. fig. 2. each fuch fibre will, as Borellus has demonr 

 flrated, lofe two-fifths of its force. But as there are 16 fibres 

 inftead of 4, their force will be as 16 multiplied by 3, to 5 mul- 

 tiplied by 4, or as 48 to 20, or as 12 to 5. 



But that the mere increafe of the number of fibres, or force 

 of the mufcles, which alone has been obferved by authors, is 

 not the fole purpofe of nature, appears from this, that in fome 

 places, and particularly between the ribs, oblique fibres are em- 

 ployed, although it is evident, that a greater number of 



ftraight 



