328 



ANIMAL MECHANICS. 



The following measurements were made from a large adult 

 lion : — 





Pectinceus Muscle (Lion). 







Length of origin, . . . 



1.70 in. 



= a. 



2- 





2-95 » 



= &. 



3- 



Length of anterior fibres, 



4-5 2 » 



= c. 



4- 



Length of posterior fibres, . . 



7.61 „ 



= d. 



5- 



Length of first diagonal, . . 



5-77 » 





6. 



Length of second diagonal, 



6.76 „ 



= f- 



Now, since a, 6 are opposite sides, and <?, d are also oppo- 

 site, and e, f are diagonals, we have, by Ptolomy's Theorem, 



but 



and also, 



ab + cd = ef ; 



ab = 1.70 x 2.95 = 5.01 

 cd = 4.$2 x 7.61 = 34.39 

 ab + cd = 3940 



(79) 



<?/*= 5.77 x 6.76=39.00. 



These results are so close as to prove that, in the Lion, the 

 adductor quartus and the adductor quintus are quadrilaterals, 

 inscribable in a circle. 



2. Man. — I made the following measurements, on a well 

 developed male subject : — 



Pectinceus Muscle {Man). 



I. 



Length of origin, .... 



. 1.82 in. 



= a. 



2. 



Length of insertion, . 



. 1.52 „ 



= b. 



3- 



Length of anterior fibres, 



. 4.70 „ 



= c. 



4. 



Length of posterior fibres, . 



. 6.30 „ 



= d. 



5- 



Length of first diagonal, 



. 5.52 „ 



= e. 



6. 



Length of second diagonal, 



. c.66 „ 



= /• 



