SINGING BIRDS. 
3 
contained oil, after which, having drawn its bill 
fucceflively over the greateft part of its feathers, 
tney thus acquire a new luftre, and become im- 
p netrable to the heavieft rains, for the water 
rolls off in large drops; 
Every part of their median ifm, as was before 
obferved, feeavs adapted for the improvement of 
their flight; their bones are extremely light and 
•thin, and. their muffles feeble, except .the large 
pe floral mufcle, by means of which they move 
their wings with Inch eafe and rapidity. This 
very itrong mufcle fills up all that ipace on. each 
fide of the breaft bone-, which, though fmah in 
quadrupeds, is, in thefe, large, broad, and exter- 
nally of a very great fur face : by means of this, 
a bird, can move its wings with a degree of 
Arength, which, when compared to the ani- 
mal’s Aze, is almoA incredible. The tail of 
birds ferves to counterbalance the head and 
ii ck, guides their flight infteadof a rudder, a d 
greatly affifts them either in their afeent, or 
when defcendi ig. 
Granivorous birds, or fuch as live upon fruits, 
corn, and other vegetables, have their mtefi; os 
differently formed from thofe of the rapat .is 
kind. Their gullet dilates juft above the bn t- 
bone, and forms itfelf into a pouch or bag, L- 
ed the crop. This is replete with falivary glands, 
which ferve to moiften and feften the ain and 
other food which it contains. Thefe glands are 
A 2 
