[ 207 ] 
contrivance for fecuring thefe circular volutions of the 
pipe, from comprefling one another, or from bending 
into angles; for, if this was the cafe, their long and 
free refpiration could not be maintained, and the end, 
for which the pipe is fo formed, would not be anfwer- 
ed. An explanation of this contrivance will be ne- 
ceflary in this place : there is a ftrong membrane, 
which arifes from all the clavicle, and is inferted all 
along the jugal bone on each fide, very ft iff like a 
drum ; and as the afpera arteria makes its anterior 
volutions between the latter, (for the pofteriour turn- 
ing is that loop within the keel of the fternum def- 
cribed,) it was neceffary that the pipe fhould be fup- 
ported by a ftay in each circular fwsep, to prevent the 
impediments juft mentioned. Accordingly there are 
three ftrong tranfverfe ligamentous membranes, run- 
ning from one jugal drum to the other ; over the outer 
of which, the pipe goes into the keel of the fternum 
through the under hole, and, in its return, rides over 
two others in a circular direction in its way to the 
thorax. Thefe are the ftays, which prevent its 
doubling back in an angle, in thefe two volutions; and 
in that within the theca, there was no need of fuch a. 
fulcrum, being fecured in its bed from any external, 
pre fture. 
This wild fwan was brought alive from Philadelphia,, 
but- died foon after its arrival ; and 1 aflifted in the 
diffedtion, and made thefe drawings from the prepared, 
parts. I find no mention of this ftrudufe of the 
a'jpera arteria in the wild fwan*, but originally in. 
* Mr. Edwards found it in the fwan he defcribes. See his 
Pillory of: Birds.. 
Bartholin,, 
