ANIMAL MECHANICS. 



351 



and by constructing this fibre, we may obtain a clear and 

 direct view of the action of the skew muscle, and, as I believe, 

 discover the reason for the invention of such muscles, and, at 

 the same time, test directly and satisfactorily the truth or 

 falsehood of the ^Postulate (p. 238). 



Making X = o, in equation (100), which gives the work 

 done by the skew muscle for any generator, we find for the 

 work done by the generator IX (Fig. 90), the following 

 expression : — 



\pj Vm*+i \PJ 



because mT = sin <h 2 ( - 

 Y \P 

 Let us now assume 



where n denotes the number of fibres, P the length of the 

 equivalent fibre, and U its distance from the point I'. Hence 

 we find 



S \W = W — p — ; (lo6) 



which represents the work done by a single fibre, n times as 

 strong as any single fibre, attached to the bone A'B' at the 

 point 0 ; , corresponding to L\ and having a length, P. 

 The only assumption in the foregoing is (105), that 



which means that the ratio of L' to P is given. Hence, there 

 are an infinite number of single fibres, any one of which 



