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Bartholin, who took delight in comparative anatomy, 
from whom Blalius has taken it. 
It is difficult to fay what may be the real ufe of this 
kind of wind-pipe in the feveral birds that have it, if 
it be not to procure them a longer retention of infpired 
air, (while they feek their food where they are obliged 
to remain fome time immerfed in water,) than if the 
pipe was firait, as in geefe, ducks, andfuch like; for 
lliefe and the river fwan often dive down to feed, yet 
it is always in ffiallow places, and their continuance 
under water is very ffiort ; whereas the wild fwan 
dwells upon and feeks his food in great lakes, and 
arms of the lea; and dives into deeper waters, and 
confcquently requires a power of continuing longer 
without refpiration than the others. 
Poets and natural hiftorians in great numbers have 
aflerted that thefe birds fing very harmonioully ; and 
this gave occafion to a friend of mine, to whom I 
iliewed thefe drawings, to furmife that this flrudture 
might be of ufe to them in tinging; but I never found 
any one who would fay they ever heard either wild 
or river fwans fing: and therefore I doubt it much. 
But, if they do ling, the length of the pipe contributes 
nothing towards it ; it is the glottis, which forms the 
voice, and modulates it, whether the pipe be long or 
fhort: befides, none of the fong, or fpeaking-birds, 
have any fledtion in their pipes, that we are acquainted 
with. 
The crane is the next I ffiall take occafion to men- 
tion, which has fuch a turning of the afpera arteria 
in the keel of the fternum ; but the volution of this 
bird is round within the bone, and may be compared 
to that of a French-horn ; whereas that of the wild 
fwan 
