Considerable evidence has accumulated in the recent years in support of the view that fat forms the chief fuel for the energy during long and sustained muscular activity '52; George and Jyoti, '53, '55, '57; and Bing, '56). It has also been shown that migratory birds store up fat in the body prior to migration (Odum and Perkinson, '51; Farner, '55; McGreal and Farner, '56; Odum and Connell, '56; Merkel, '58) and that fat is reduced during migration (Williamson, '52, '55). The pectoralis muscle of flying birds and other highly active muscles such as the breast muscle of the bat and the fight muscles of insects and the vertebrate heart muscle have been shown to contain a high concentration of a fat splitting enzyme lipase (George and Scaria, '56, '57; George, Susheela and Scaria, '58; George, Vallyathan and Scaria, '58; George and Bhakthan, '60; George and Iype, '59). The presence of high concentration of lipase in these muscles is therefore of special significance.
The breast muscle of flying birds also contains high concentrations of the oxidative enzyme, succinic dehydrogenase (SDH) (George and Talesara, '61a). The higher SDH activity (George and Talesara, '61a) and an increased storage of fat in the liver (Naik, '63) and the breast muscle (Vallyathan, '63) have also been noted in the pre-migratory period of the Rosy