[ 2IJ ] 
malSj called amphibious ; and although a bird and a 
fnake are not the lame, in the confcrudtion ©f the 
refpiratory organs, yet the circU-mftance of the air 
palling beyond the lungs, into the cavity of the 
abdomen , in both, naturally leads us to fuppofe, 
that fo fimilar a ftrudure is defigned for the fame 
purpofe in both ; and this analogy is further con- 
firmed by the texture of the lungs in both, which 
con lift of large cells. Now in amphibious animals, 
the ufe of this conformation of the lungs is evi- 
dent; for it is in confequence of this, that they 
can breathe lefs frequently than others. Confidering 
the matter in this light, it may flill, in birds, 
have fome connexion with dying ; for that motion 
may eafily be imagined, to render frequency of 
refpiration difficult j and may, therefore, make a re- 
fervoir of air Angularly ufeful. 
It may, perhaps, occur to fome, that the whole 
of thefe communicating ceils are to be confiafered 
as extended lungs ; but I can hardly think, that any 
air, which gets beyond the veficulated lungs them- 
felves, is capable of affedi ng the blood of the ani- 
mal ; as the other cavities, into which it comes, as 
well thofe of the foft parts, as of the bones, are- 
very little vafcular. 
How far this conftrudion, of the refpiratory or- 
gans, may affilt birds' in Anging", is worthy of con li- 
beration, as the vaft continuance of fong, between 
the breathings, in a canary-bird, would appear 
to be owing to thiscaufe. 
At prefent, I fhall purfue this fubjed no farther ; 
but leave it to a fubfequent paper, as requiring a 
great many comparative fads,- to. efbablifh the final 
caufe. 
NXX. M. D" luc’ s 
