120 Dr. LaTHAM’s Effay on the Trachea or Windpipes of Birds. 
The trachea here is more confpicuous on account of the bony 
dilatation in the middle of it than for any other circumftance: in- 
deed a manifeft difference from any other may be obferved juft below 
the /arynx, being an oblong bony cavity of nearly an inch in length. 
From this part the #rachea defcends for near two-thirds of its length, 
when it fwells out into a {trong bony hollow, flat on one fide, and 
moderately convex on the other, about the fize of a {mall walnut. 
At the divarication the parts again lofe their rings, and become bony, 
not greatly enlarged, but equally fo on both fides—the two éron- 
chie taking rife at the under part of this laft bony hollow. 1 have 
obferved fome diverfity in the ¢rachee of this fpecies, and in one in 
particular the hollow round bone was lefs offified; befides which, the 
oblong bone next the /arynx differed much in being fhorter, (Fig. 6.) 
as alfo the bony part at the bifurcation of fcarcely more than half 
the dimenfions, (Fig. 7.)—which laft circumftances taken together 
feemed to prove its being a young bird. 
WE now clofe the account of fuch fpeties of the Duck Tribe 
as the males of them have fomewhat in the conformation of the 
trachea differing from the other fex; and I flatter myfelf, that, 
by means of the preceding defcriptions, aided by engravings of the 
parts in queftion, the reader will find every thing as clear as was 
reant to be. 
Endeavouring to add to this lift, I have examined feveral others of 
the Duck genus, as the Grey Lag, White-fronted, Bean, Bernacle, 
Brent and Scoter; in none of which have I ever found any thing 
remarkable. —But I mean not to defift from the enquiry, and recom- 
mend attention to it by others; for I truft that many fingular and 
curious occurrences will be difclofed on.a further inveftigation of the 
fubject. 
Wk 
