fig 88.) 
CLASS II. AVES. 
Remarks. Animals of this class do not have 
their lungs divided into lobes—the whole being in 
a single mass. Neither are their lungs ventilated 
by their own contractions and dilatations. Air is 
made to pass through them by the action of other 
organs. It is admitted to the blood by an infinite 
number of vessels from the axils of the wings and 
various other parts of the body. 
Their forms are adapted to their peculiar cir- 
cumstances ; they being the only animals of this 
grand division which travel in the atmosphere. 
The muscles of the breast are very large and 
strong, giving great force to their wings. Their 
covering of feathers, being non-conductors of elec- 
tric fluid, secures them in some measure against 
its frequent discharges in the form of lightning in 
the upper regions ; and more especially when sit- 
ting upon their nests, on high trees. | 
Their rapid passage through different regions 
of the air, and its perpetual action upon them, af- 
ford them the means of progunosticating the varia- _ 
tions of the atmosphere by a method totally un- 
known to us. 
| Tue cLuass AVES Is DIVIDED INTO SIX ORDERS. 
ORDER I. ACCIPITRES. 
Having strong hooked beaks and claws ; toes 
4; the thumb toe, and inner one of the other three, 
are larger. Birds of prey. 
Vuxrour, (vulture,) bill straight, hooked at the 
tip, and covered at the base by a cere or skin ; 
