ANIMAL MECHANICS 



385 



(or nearly so) to the axis SC, and let us use the following 

 notation : — 



CY=b, CX = a, 



XCY=$ y YP = y, XP = x. 



It is easy to see that we have the following relations : — 



y 2 — x 2 = b 2 - a 2 , 



y 2 + x 2 = b 2 + a 2 - lab cos 0, 



from which we obtain 



V_ = lb (b - a cos 0) 

 # \a (a- 6 < 



(«- b cos 0) 



Work done 



Maximum work 



= sm 2(7. 



Substituting, in the foregoing, the following observed 

 values, 



a = 4.29 in., b = 4.30 in., <p = g° 30', 

 we obtain 



| = tan (49°45 / ) > 



Work done „ _ 



sm 20 = ^ — ; — r = 08.63 P er cent - 



Maximum work 



7. Obturator externusi — This muscle has the usual origin, 

 and is inserted into the deepest portion of the pit of the great 

 trochanter ; it may be regarded as a triangular muscle, and the 

 proportion of the work done by it to the maximum work 

 possible may be found by measuring the distances from the 

 insertion and central point of origin from the centre of the 

 socket. We thus find — 



Distance from insertion to centre of socket = 2.33 in. 



From centre of Obturator foramen to centre of socket = 2-27 ,, 

 2 c 



