[ 206 ] 
body to lye upon the fternum, and terminating in 
the lungs ; whereas, in thefe birds, which are the 
fubje&s of this difccurfe, they have certain turnings 
within the fternum or breaft-bone, and run back again 
to double up into the thorax : which elongates them 
to double the length of thofe in other birds of equal, 
nay of greater magnitude, than the birds that have 
them. 
In the wild fwan, the wind-pipe runs down from 
its upper extremity under the epiglottis, in company 
with the oefophagus, till it comes within about four or 
five inches of the laft vertebra of the neck ; here the 
pipe quits the oefophagus, (which keeps its courfe to 
the inteftines) and makes a convex curve forward 
between the offa jugalia, in a circular fweep, till it 
enters into a hole formed through a ftrong membrane 
in the center between the infertions of the ofta juga- 
lia into the fternum under the bread:; and, in that 
circular fweep, is covered clofely by the fkin, fo, that, 
in that place, a very flight blow would deftroy the 
bird. 
This hole is the beginning of a theca or cavity in 
the keel of the fternum, in which the pipepaftes on to 
the end, and then returns back, forming a loop 
which is circular; and, palling out by another hole 
through the fame ftrong membrane, makes another 
circular fweep within, and parallel to the exterior one, 
and then riles in that round direction, till it enters the 
cavity of the thorax, and is divided into two 
branchiae, which terminate in the lungs. 
When one views this ftrudture, it is impoftible to 
avoid being furprized at the wonderful formation of 
this part, efpecially too if we attend to the noble 
contri- 
