ANIMAL MECHANICS. 



421 



of the joint in such a position as to give the muscle the maxi- 

 mum amount of advantage in performing its work. The mus- 

 cles that lift the wing are the Deltoid and Pectoralis avium 

 which latter corresponds with the Subclavius in Mammals. 



Combining together the Depressor and Levator muscles 

 I have found the following interesting results : — 



Depressor and Levator Muscles in the Wings of Birds. 





Depressors. 



Pect. major 



and 

 Pect. minor. 



Levators. 



Deltoid 

 and 

 Pect. avium. 



Ratio. 





64-43 



10. 18 



15. 80 per cent 





6 4-55 



13.36 



20.70 



3. Dorking Fowl, . . 



58.00 



22.67 



39- °9 „ 



4. Aylesbury Duck, . . . 



63.84 



15.03 



23-54 ,. 





67.56 



8.82 



1 3«°6 „ 





57.62 



19.90 



34.54 





63.90 



14.74 



23.07 





66.68 



12. 81 



19 21 „ 



9. Common Heron, . . . 



68.99 



10.83 



J5-70 „ 



10. Squacco Heron, . . . 



74- 17 



10.91 



H-7 1 » 





63.59 



15. 9 2 



25-04 



12. White-headed Eagle, 



61.39 



14.54 



23.68 





75-82 



r 1 26 



14.84 „ 



14. African Parrot, .... 



69. 14 



1596 



23.08 „ 





59-2^ 



17.22 



2 9-°5 



16. White Crane, .... 



54.90 



20.95 



38.16 „ 



i 



38.28 



20.00 



52.25 



The birds in which the great pectoral becomes least are 

 the Dorking Fowl and Curassow, which are notoriously heavy 

 fliers, and the Weka Rail, which uses its wings principally in 

 propelling itself through the long grass. The birds of 

 greatest soaring power are those in which the levator muscles 

 bear the least proportion to the depressor muscles, viz., the 

 Gannet, Grebe, Heron, and Albatross. 



If we arrange the muscles Wto groups, as before, we find 

 the following Table : — 



