66q. ANATOMY, f Comparative, 
Not long before'the excktlion of the chick, the whole 
yolk is taken into its abdomen. The whole albumen and 
vitellus are not confumed by the chick : for fome part of 
the humours of the egg efcapes through the fhell, and is 
not lupplied by any tiling from without; as evidently ap¬ 
pears by an "egg’s becoming fo much fpecifically lighter 
as to fwiin in water after incubation, though it funk in it 
when recent. 
The chalazae remain long without being conliderably 
changed, unlefs that they are brought nearer to each other 
by the crefccnt form of the yolk; at la(t they degenerate 
into a dry chalky fuMance. The cicatricula very foon is 
enlarged by incubation ; and, being buoyed up oil the top 
of the yolk to the fuperior part of the egg, it is placed 
very near to the air-bag ; and, when both increafe, they 
become contiguous. The cicatricula is called amnios, when 
it becomes large, and contains the colliquamentum or li¬ 
quor in which the chick is immerled. The quantity of 
the colliquamentum gradually increafes till the fifteenth 
or fifteenth day of incubation; on the eighteenth, it is all 
confumed; and, in the three following days, fcarcely any 
moifture can be obferved on the internal furface of the 
amnios. The liquor of the amnios is more clear and tranf- 
parent than the colliquated white; its talle is more fait, 
and it has no obfervable fmell. Its confidence is at firft a 
little vifeous, then it becomes more fluid, and afterwards 
turns a little ropy again. We can fay nothing of the par¬ 
ticular times when it does or does not coagulate by heat : 
for it is in fo (mail quantity during the greater part of the 
time of incubation, that one can fcarcely gather as much in 
a fpoon as is fit to make any experiment with: and when 
all the egg is boiled hard, it adheres fo clofely to the white, 
that it is hardly poflible to difiinguifh the one from the 
other. Malpighius, fpeaking of the egg between the four- 
teenth and nineteenth day, lays, “ That this thin diapha¬ 
nous liquor of the amnios was fometimes forced, by boil¬ 
ing, into a white tarty fubrtancewhich Dr. Monro’s 
trials alfo confirmed. 
The allantois and its contained urine are to be feen in 
an e< TO ', as well as in the fecundines of viviporous animals. 
Though the heart is among the firrt parts of the chick that 
can be diltinguirtied, yet the umbilical velfels are feen 
much about the fame time that the heart is obferved. The 
umbilical velfels gradually difperfe their branches upon 
the amnios, upon the vitellus, and upon the membranes 
of the albumen: the extremities of the much greater num¬ 
ber, being immerfed into the white, are extended propor¬ 
tionally as it is colliquated. Near the end of incubation, 
the umbilical velfels begin to fhrivel and decreafe, till at 
The exclufion they are very fmall. 
The embryo is feen in an egg at firft in the form of a 
fmall worm : then its carina or (pine, with the large pro¬ 
minences, that afterwards Ihew themfelves to be the brain 
and eyes, appear ; the other bowels feenr hanging from the 
fpine ; the chafm of the mouth difeovers itlelf; the extre¬ 
mities fprout out; the vifeera are gradually covered with 
the integuments ; and at laft the beak, nails, and feathers, 
are feen; after which all the parts become ftronger and 
firmer, the proportional bulk of the head decreuling. Af¬ 
ter all the parts of the chick are formed, it is always found 
lying on the fide, with its neck greatly bent forward, the 
head being covered with the upper wing, and the beak 
placed between the thighs. When the (hell is opened af¬ 
ter the chick is large and ftrong, it may be feen to bounce 
and fpurn, fometimes opening its mouth wide, efpecially 
if it is ftirred or pricked. The mouth, oefophagus, and 
ingluvies, are always found moift ; but never contain any 
quantity of liquor that can be collected or will run out in 
drops. The bulbous glandular part of the oefophagus 
immediately above the ftomach, or what Payer calls the 
infundibulum , and the ftomach, are full of a liquor, in the 
youngeft chick we can diflect, and continue full the whole 
time of incubation; neither infundibulum nor ftomach 
having yet the tendinous firmnefs they have in adults ; 
nor can we obferve the dry pellicle which is fo eafily fepa- 
rated from thefe parts in hens. This liquor of the fto¬ 
mach is at firft thin and more watery ; afterwards it be¬ 
comes curdy; and at laft refembles a greyiih white mucus, 
unlefs that fome part of it frequently is coloured yellow 
or green by a mixture of bile. It always coagulates, by 
boiling, into a firm yellowifti white fubrtance. A little 
time before the exclufion, the chick may frequently be 
heard making the fame piping found that hatched chick¬ 
ens make. In three eggs, which were opened in this ftate, 
the beak of the chick had perforated the membrane of the 
folliculus asris. The lhell at the obtufe end of the egg 
frequently appears cracked fome time before the exclufion 
of the chick. The chick is fometimes obferved to perfo¬ 
rate the (hell with its beak; but in thole Dr. Monro favr 
tumbling out of the lhell, it was broke oft' irregularly, at 
the place where the membrane of the folliculis aeris was 
joined to it. After the exclufion the yolk is gradually 
wafted, being conveyed into the fmall guts by a fmall duff, 
its membranes gradually contradf themfelves, and the duct 
becomes Ihorter. On the tenth day after exclufion, the vi¬ 
tellus was no larger than a fmall pin’s head, and the duct 
was fcarcely one-twentieth part of an inch long. 
From this hiftory of the egg, we lhail endeavour to de¬ 
duce the manner in which the colliquated white is taken in 
by the chick. Authors generally feem to agree, that the 
oviparous foetus, while very young, receives its nourifh- 
ment by the navel; but feveral of the belt reputation have 
been of opinion, that afterwards it is conveyed by the 
mouth. Let us examine the arguments they have tiled in 
proof of this, and then fubjoin fome negative reafons 
which they have not noticed. 
Bellini has deferibed the cicatricula, or facculus amnii, 
with the chalazae firft formed in the back of the hen ; to 
which, according to him, the vitellus is afterwards joined, 
and the white is acquired as they pafs down the oviduct. 
He fays, the chalazae are compoled of numerous canals, 
which open into the amnios, and fend out their roots into 
the cavity of the yolk, and into the white. It is eafy to 
conceive what confequences may be drawn from this de- 
feription, by thofe who aflert the nourilhment to be car¬ 
ried by the mouth, viz. That here are diredt paftages in¬ 
to the cavity where the chick is, which can take up the 
liquors no other way than by the mouth. We deny, how¬ 
ever, that the facculus amnii is formed before the vitellus; 
on the contrary, the vitellus is evidently to be feen before 
the cicatricula or chalazae can be difcerned. We alio deny 
the chalazae (if they are canals) to have the leaft commu¬ 
nication with the amnios, at any time, or in any ftate of 
the egg, otherwife than as they are both adhering to the 
membrane of the vitellus ; upon which, or within which, 
no particular fibres, no canals, are ftretched to the cica¬ 
tricula. Every one has it in his power to examine thefe 
fadts. If then the fadls are denied, the confequences can¬ 
not be admitted. 
Since there are no canals palling through the yolk, that 
open into the faccus colliquamenti, and the cicatricula comes 
to be placed on the upper part of the yolk, and contiguous 
to the air-bag, it is evident, that the liquor amnii mull be 
furniihed by the chick, which being covered with feathers, 
having no mammas, bladder of urine, or large falivary 
glands, can only fupply it by the branches of the umbili¬ 
cal velfels fpread on the amnios. Harvey affirms, that a 
liquor is found in the mouth and ingluvies of the chick, 
which he concludes to be the colliquamentum or iiquor 
amnii, from their refemblance ; from the quantity of the 
contents of the ftomach ; from the chick’s being feen to 
open its mouth; and from the necelfity creatures are in of 
fwallowing, or of forcing back by vomiting, whatever is 
introduced to the root of their tongue. As to the refem¬ 
blance, we do not fee how the comparifon can be made, 
fince the liquor in the mouth and crop is in fuch a fmall 
quantity. But, fuppofe that a fufficient quantity was col- 
ledfed, the two liquors agreeing in their feveral properties 
would not of itfelf be a fufficient proof of their being the 
fame ; and if, for argument’s fake, the liquor in the crop 
was 
