952 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. 
Wuenre the fibres of mufcles run obliquely, it is evident, 
and has been obferved by Boret.us 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. 1. the force of this mufcle may be reprefented by the 
number 4. 
Ler 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 fhall, by doing fo, form 16 
ropes or fibres. 
Let us next fuppofe, that thefe ropes, Yoprefesthiig 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 demon- 
ftrated, lofe two-fifths of its force. But as there are 16 fibres 
inftead of 4, their force will beas 16 multiplied by 3, to 5 mul- 
tiplied by 4, or as 48 to 20, or as 12 to 5. 
Bur 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 
