36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I43 



Although the size of a muscle is inherited through many generations 

 and is usually related to the activity, this is not always so. In a com- 

 parison of domesticated and wild forms in the same families, we find 

 that in the domesticated parakeet, Melopsitticus undulatus, the various 

 values are similar to those of the wild forms, while in the domestic 

 fowl, Gallus gallus, the pectoral muscles and wings are much smaller, 

 but the leg muscles are equal to those in wild species of the family. 

 Although the parakeet leads a rather inactive life, it is not far removed 

 from its wild ancestor. On the other hand the domestic fowl has 

 passed through countless generations of selective breeding. 



In conclusion, our observations show that muscle weights are re- 

 lated to the activities of the bird. Since the heart is the driving force 

 that circulates oxygen and nutrients and removes waste products, a 

 small heart limits activity, while a large heart can maintain it much 

 longer. In other words, heart size indicates staying power. The flight 

 muscles tend to parallel the performance in the air, or at least the 

 ability to perform. The area of the wings together with their aspect 

 ratio gives further indication of their use. Finally, the relative weight 

 of a muscle or group of muscles, and the wing areas together with 

 their aspect ratios, appear to be just as characteristic of a species as 

 is the body weight. 



LITERATURE CITED 



American Ornithologists' Union Committee. 



I 957- Check list of North American birds, 5th ed. 

 Aymar, G. C. 



1935. Bird flight. New York. 

 Beddard, F. E. 



1898. The structure and classification of birds. New York. 

 Bent, A. C. 



1922. Life histories of North American petrels and pelicans and their allies. 

 U.S. Nat. Mus. Bull. 121. 

 Convreur, E., and Chapeaux. 



1926. Conditions of sustained flight in pigeons. C. R. Soc. Biol., vol. 94, 

 pp. 1160-1161. 

 Demoix, R. 



1930. Flight in large and small birds. Zeitschr. Biol., vol. 90, pp. 199-230. 

 Eisenmann, E. 



1955. The species of Middle American birds. Trans. Linnaean Soc. New 

 York, vol. 7. 

 Fisher, H. I. 



1946. Adaptations and comparative anatomy of the locomotor apparatus of 

 New World vultures. Amer. Midland Nat., vol. 35, pp. 545-727. 



