ANIMAL MECHANICS. 285 



Hence we have 



IW'^P^Mu^Y (62) 



In the case of the pectoral muscle of the Albatross, I found 

 by measurement — 



$ld6 = 7. 17 inches. 

 20 = 47°. 

 p = 129 0 . 



Introducing these values into equation (62), and solving for b, 

 we find 



7.17 



b = ■ ; = 8.IQ17 inches. 



. . tan 76 0 i*' 3 ' 



sin (129 0 ) log e ■ 0 



v * ' 0 tan 52 45 



The right line^ 7 ^" is drawn, in Fig. 76, parallel to AB, and 

 intersecting the bisector OX, at the distance just found, from 

 the vertex 0. 



A straight bone. A"B'\ acting as the origin of the quadrila- 

 teral pectoral muscle, would produce upon the wing bone, 

 A'B\ a mechanical effect similar to that of the curved bone, 

 AB ; but it would, obviously, cause much inconvenience by 

 its awkward shape and length. Hence we see the reason for 

 the curved outlines of many bony origins of muscles, which 

 frequently occur in Nature. The curved bone fits into a 

 smaller space, gives rounded outlines to the structure, and at 

 the same time produces all the mechanical effects of the 

 straight bones, which mathematicians use in their calculations ; 

 and we are obliged, in order to interpret Nature, first to 

 translate the expressive language of her beautiful and sym- 

 metrical curves, into the less perfect language of the rigid 

 lines and bars used by geometers. 



