332 On some Elementary Principles in Animal Mechanics. [May 2, 



sected animals, and the biquadratic coefficients then calculated, with the 

 following results. 



1. Llama. Adductor secundus (/3) : — 



-0-116\ 4 + 3'375/\ 3 + 4-903X+0-042=0 ; 

 root, X= -0-0085. 



2. 'Master Macgrath"*. Adductor secundus (/3) : — 



-0-479X 4 + 2 < 395\ 3 + 2-128\ + 0'135=0; 

 root, \= -0*063. 



3. Woman. Adductor secundus (Jj) : — 



-0-153\ 4 + 5'288\ 3 + 3710\+0-040=0; 

 root, X= — 0-011 . 



4. African Leopard. Adductor secundus (/3) : — 



+ l-372X 4 +l-343/\ 3 +l-091\- 0'077 = 0; 

 root, \=+0'07. 



5. Lion. Adductor secundus (/3): — 



-0-647A 4 + 5-456\ 3 + 4-495\ + 0-405 = ; 

 root, X=-0-09. 



The position of the points O and O' being determined, I found, by calcu- 

 lations too long to give in an abstract, the relation between the work actually 

 done by the muscle and the maximum work possible, with the following 

 satisfactory results : — 



Work done expressed in 

 Muscle. percentage of maximum possible. 



Adductor secundus (/3) : — 



1. Llama 99*63 per cent. 



2. " Master Macgrath " .. 9878 „ 



3. Woman 99'86 



4. African Leopard 97*13 „ 



5. African Lion 97*92 „ 



Adductor secundus («) : — 



6. African Leopard 99*98 „ 



7. African Lion 98*88 „ 



Adductor primus : — 



8. African Lion 97*70 „ 



Skew muscles are only employed in nature as a supplemental contri- 

 vance ; and they differ from all other muscles in this respect, that whereas 

 the equivalent fibre of any other muscle always coincides with some real 

 fibre of the actual muscle, the equivalent fibre of the skew muscle does 

 not coincide with any actual fibre, but, on the contrary, may lie completely 

 outside the muscle. Hence the skew muscle is used to produce an addi- 

 tional force along O O f , where the points O and O' are already occupied 

 for other purposes ; and in producing this force along O O' portions of bone 

 A B, A' B' at a distance, and not occupied for other purposes, are made 



* Lord Lurgan's famous greyhound. 



