ORGANS OF BREATHING. 
63 
are of a more firm and compact texture. At the same 
time they are most plentifully supplied with air- 
cells, communicating with other cells, profusely dis- 
tributed over every part of the system, by which 
their bodies are in a manner blown up and rendered 
buoyant ; a considerable portion of the skeleton 
moreover, as we have shown, being formed into re- 
ceptacles for this light and elastic fluid, of which 
birds partake in so much greater a degree than most 
other parts of the creation. In fact, a bird, destined 
as it is to live in air, may he almost called an abso- 
lute air-vessel, so completely does air fill up and 
circulate throughout its whole frame. While men 
and other land animals breathe in air through the 
nostrils alone, a bird respires through a variety of 
other channels. A wounded Heron was observed 
to live a whole day, breathing solely through a 
broken portion of the wing-hone *. Other experi- 
ments have confirmed the fact ; the fractured portion 
of a hone that had been separated, when immersed 
in soap and water, was observed to emit bubbles from 
the part nearest the body, proving beyond a doubt 
that it contained air in considerable quantities. 
The quills of the feathers are also air-vessels, 
which can be emptied and filled at pleasure. 
There is a bird called the Gannet, or Solan-Goose, 
which is a beautiful instance of this wonderful pro- 
vision ; it lives on fish, and passes the greater part 
of its time either in the air or on the water, even in 
the most tempestuous weather, when it may be seen 
floating like a cork on the wildest waves. To enable 
it to do so, with the least possible inconvenience, it 
* See Linncean Transactions , vol. xi., p. II. 
