666 A N A T 
Thefe creatures, as was obferved of fowls in general, 
have no teeth. Some, indeed, have an appearance of 
teeth ; but thefe are only fmall proceifes or ferrae rifing 
out from the mandible, without any focket, &c. which 
would have been needlefs, as they fwallow their food en¬ 
tire. But their tongue is made fomewhat firm, left it 
fhould be hurt by the fharp points of the grain on which 
they feed. It is of a triangular figure, and pointed be¬ 
fore ; and, as by their depending pofture their meat is in 
hazard of falling out of their mouths, to prevent this, 
there are feveral fmall pointed papillae (landing out upon 
their tongue and palate, with their points inclined back¬ 
wards, allowing an eafy paftage to the food, but hindering 
it to return. We have here no velum palatinum, uvula, 
or epiglottis ; and, in place of two large holes opening into 
the nofe, there is only a long narrow rima furnilhed with 
ftrong mufcles ; and a fimilar rima fupplies the place of a 
glottis. Fowls have a power of Ihutting both at pleafure; 
the nature of their food feems not only to exempt them 
from the hazard of its getting into the nofe or trachea, but 
its fharp points would hurt an uvula or epiglottis. Hence 
we fee with w hat difficulty they fwallow dough or other 
fort of food that can be eafily moulded into any form. 
When we examine the upper end of the trachea, we ob- 
fervc a rima giottidis with mufcular Tides, which may adt 
in preventing the food or drink from palling into the lungs, 
for there is no epiglottis, as in man and quadrupeds. 
Their cranium is more cellular and cavernous than ours. 
By this means their heads are light, yet ftrong enough to 
refill external injuries ; for the enlarging of the diameter 
of bones contributes to their ftrength. By this cavernous 
cranium the organ of fmelling is fuppofed to be confidera- 
bly enlarged ; and farther, finging birds, as is obferved by 
Mr. Ray and Mr. Derham, have the cavernous Itrudtwre 
of the brain ftill more obfervable : and we are told that 
the cavity of the tympanum communicates with the cells. 
Their brain is covered with the common membranes, but 
its external furface is not formed into fo many gyrae or 
convolutions as ours. Its anterior part is quite folid, of a 
cineritious colour, and fo far refembies the corpora jlriata 
as to give rile to the olfactory nerves. The whole of it 
appears to us as imperfect, and we can fcarcely determine 
whether there be any thing analogous to a third or fourth 
ventricle; neither the corpus callofum, fornix, nates, or tefes, 
&c. can be obferved here ; which parts therefore cannot be 
imagined as abfolutely neceftary for the fundtions of life, 
fince we find thefe creatures perform them fufficiently well. 
Their organ of fmelling is very large, and w ell provided 
With nerves; hence they have this fenlation very acute. 
Ravens and other birds of prey give a fure proof of this, 
by their being abie to find out their prey, though conceal¬ 
ed from their fight, and at a confiderable diftance. Thofe 
birds that grope for their food in the waters, mud, &c. 
have large nerves, which run quite to the end of their 
bills, by which they find out and diftinguilh their food. 
The anterior part of their eyes, inftead of having the 
fclerotic coat contained, fo as to make nearly a fphere as 
an us, turns all of a fudden fiat; fo that here the fclerotic 
makes but half a fphere; and the cornea rifes up after¬ 
wards, being a portion of a very fmall and diltindl fphere: 
fo that in thefe creatures there is a much greater difference 
between the fclerotic and cornua than in us. Hence their 
eyes do not jut out as in man and quadrupeds. As moll 
of thefe creatures are continually employed in hedges and 
thickets, that their eyes might be fecured from thefe inju¬ 
ries, as well as from too much light when flying in the 
face of the fun, there is therefore a very elegant mechan- 
ifm in their eyes. A membrane rifes from the internal 
canthus, which at pleafure, like a curtain, can be made to 
cover the whole eye; and this, by means ot a proper mufcle 
that rifes from the fclerotic coat, and, palling round the 
optic nerves, runs through the mu/culus oculi attolens and 
palpebra, to be inferted into the edge of this membrane. 
Whenever this nuifde ceufes to acl, the membrane by its 
O M Y. [Comparative. 
owm elafticity again difcovers the eye. This covering is 
neither pellucid nor opaque, both which would have been 
equally inconvenient; but, being fomewdiat tranfparent, 
allows as many rays to enter as to make any objedt juft vi- 
fible, and is fufficient to diredt them in their progreliion. 
By means of this membrane it is that the eagle is faid to 
look at the fun. Quadrupeds alfo have a fmall membrana 
niB.it ans. 
Befides, all fowls have another particularity, the ufe of 
which appears not fo well underllood; and that is, a 
longifh black triangular purfe, rifing from the bottom of 
their eye juft at the entry of the optic nerve, and ftretched 
out into their vitreous humour, and perhaps it gives fome 
threads to the cryftalline. To this the French (who were 
the firft that took notice of it in their dilfedlions before the 
Royal Academy) gave the name of bourfe noire. It may 
poffibly ferve to fuftocate fome of the rays of light, that 
they may fee objedts more diftindtly w ithout hurting their 
eyes. It has a connedtion with the vitreous, and feems to 
be joined alfo to the cryftalline, humours. If we fuppofe 
it to have a power of contradlion, (which may be as well 
allowed as that of the iris,) it may fo alter the pofition of 
the vitreous and cryftalline humours, that the rays from 
any body may not fall perpendicularly upon the cryftal¬ 
line; and this feems to be neceftary in them, lince they 
cannot change the figure of the anterior part of their eye 
fo much as we do : and, as this animal is expofed often to 
too great a number of rays of light, fo they have no ta- 
petum, but have the bottom of their eye wholly black on 
the retina; and in confequence of this, fowls fee very ill 
in the dark. 
They have no external ear; but in its place a tuft of 
very fine feathers covering the meatus auditorius, which 
eafily allows the waves of found to pals them, and like- 
wife prevents dud or any infedl from getting in. An ex¬ 
ternal ear would have been inconvenient in their paftage 
through thickets, and in flying, &c, A liquor is lepara- 
ted in the external part of the ear, or meatus auditories, 
to lubricate the paftage, and farther prevent the entrance 
of any infedls, &c. The membrana tympani is convex exter¬ 
nally; and no mufcles are fixed to the bones of their ear, 
which are rather of a cartilaginous confidence: any tremu¬ 
lous motions impreffed on the air are communicated in 
thefe creatures merely by the fpring and elafticity of thefe 
bones; fo, probably, the membrane is not fo ftretched as 
in the human ear by mufcles. The femicircular canals 
are very diflindl, and eafily prepared. 
We (hall next confider carnivorous birds, commonly 
called birds of prey ; and for an example (hall take a llan- 
nel or fmall hawk. The principal difference to be ob¬ 
ferved in them, is in their chylopoietic vifcera, which 
may be accounted for from their different way of life. 
Immediately under their clavicles, we obferve the cefo- 
phagus expanded into their ingluvies, which is propor¬ 
tionally lefs than in the granivorous kind, fince their food 
does not fwell fo much by maceration : and for the fame 
reafon, there is a lefs quantity of menftruum to be found 
there. They have alfo a ventriculus fuccenturiatus, plenti¬ 
fully llored with glands, fituated immediately above their 
Itomach, which is much more thin and mufculo-membra- 
nous than in the granivorous kind ; and this difference, 
which is almoft the only one we find between the two dif¬ 
ferent fpecies of fowls, is eafily accounted for from the 
nature of their food, which acquires lefs attrition, being 
ealier of digeftion than that of the other kind ; neverthe- 
lefs, it feems requifite it fhould be lironger than the hu¬ 
man, to compenfate the want of abdominal mufcles, which 
are here very thin. The fame mechanifm obtains in this 
creature’s duodenum, that we have hitherto obferved. As 
being a carnivorous animal, its guts are proportionally 
lliorter than thole of the granivorous fpecies, for the reafon 
firft given, viz. its food being more liable to corrupt, is 
therefore not proper to be long detained in the body ; and 
for that reafon it has no inteftina caeca, of which the other 
1 fowls 
