Comparative.] A N A r 
otherwife certainly do at this time. There are mucous 
glands placed here to fecern this gluten, which on the 
breaking of the membranes with the contained waters make 
a fapo that lubricates and waflies the parts, and makes 
them ealily yield. The fil'd of the proper involucra of 
the foetus is the chorion. 
The chorion is a ftrong firm membrane, on whofe exter¬ 
nal furface are difperfed a great many red flefhy bodies of 
the fame number, lize, and ftrufture, with the papillae, 
with which they are mutually indented. They have been 
called cotylcdones, from aort> 7 wj, “cavity.” This is greatly 
difputed by fome authors as a name very improper; but 
we think without reafon, lince the furface that is conneCt - 
ed to the papillre is concave, though when feparated it ap¬ 
pears rather convex. To fiiun all difpute, they may be 
called properly enough placentulae, fince they ferve the fame 
ufe as the placenta in women. The reparation of thefe 
from the papillae without any laceration, and our not being 
able to injedt coloured liquors from the velfels of the glands 
of the uterus into the placentulae, feem to prove beyond 
a reply, that there can be here no anatlomofes between 
the veflels: on their coats run a great number of velfels 
that are lent to the feveral placentulae, on the external fide 
next to the uterus; whereas in creatures that have but 
one placenta, as in the human fubjedt, cats, dogs, See. the 
adhefion is fomewhat firmer. The placentae are likewile 
joined to the papillae in the cornua uteri. 
The allantois is a fine tranfparent membrane contiguous 
to the former. Jt is not a general involucrum of the foe¬ 
tus in the mother, for it covers only a lYnall part of the 
amnios. It is moftly lodged in the cornua uteri. In mares, 
bitches, and cats, it furrounds the amnios, being every 
where interpofed between it and the chorion. In Iheep 
and goats it is the fame as in the cow; and in fwine and 
rabbits it covers ftill lefs of the amnios. This lac is pro¬ 
bably formed by the dilatation of the urachus, which is 
connected at its other end to the fundus of the bladder, 
through which it receives its contents; and a great quan¬ 
tity of urine is commonly found in it. The membrane is 
doubled at the extremity of the canal, to hinder the re¬ 
turn of the urine back into the bladder. Its velfels are 
fo excelfively fine and few, that we cannot force an inject¬ 
ed liquor farther than the beginning of this coat. This 
membrane is fo far analogous to the cuticula, as not to be 
liable to corruption, or ealily irritated by acrid liquors. 
The third proper integument of the foetus is the amnios. 
It is thinner and firmer than the chorion; it has numerous 
ramifications of the umbilical velfels fpread upon it, the 
lateral branches of which feparate a liquor into its cavity. 
This is the proper liquor of the amnios; which at firft is 
in a fmall quantity, afterwards increafes for fome months, 
then again decreafesq. and, in a cow near her time, the 
quantity of this liquor is not above a pound. This mem¬ 
brane does not enter the cornua uteri in this creature, be¬ 
ing confined to the body of the uterus; whereas the allan¬ 
tois occupies chiefly its cornua. There are two vena um- 
bilicales , and but one in the human fubjedt; becaufe the 
extreme branches coming from the feveral placentulae 
could not unite fo loon as they would have done had they 
come all from one cake as in the human. There is a fmall 
round flefhy body that fwims in the urine of cows, mares, 
&c. which is the hippomanes of the ancients. Several idle 
opinions have been entertained as to its ufe; but that feems 
to be ftill unknown, or how it is generated or nourilhed, for 
it has no connection with the foetus or placenta. 
The umbilical vein joins the vena portarum in the cap- 
fula Gliffoniana, without fending off any branches as it 
does in the human fubjedt. This vein loon after birth 
turns to a ligament; yet there are fome inftances where it 
has remained pervious for feveral years after birth, and 
occafioned an haemorrhage. We may next obferve the 
duet called canalis venofus, going ftraight from the capfu- 
Ja Gliffoniana to the vena cava ; this turns alfo afterwards 
to a ligament. The umbilical arteries rife at acute angles 
O M Y. 659 
from the internal iliacs, whatever fome may fay to the 
contrary'; thefe alfo become impervious. 
The pulmonary artery coming from the right ventricle 
of the heart divides into two: the largeft, called canalis 
artcriofus, opens into the defeending aorta; the other di¬ 
vides into two, to ferve the lungs on each fide. The force, 
men ovale, is placed in the partition between the right and 
left auricles. At the edge of the hole is fixed a mem¬ 
brane, which when much ftretched will cover it all over; 
but more ealily yields to a force that aCts from the right 
auricle to the left, than from the left to the right. After 
what has been faid, we may ealily underftand how the 
circulation is performed in a foetus. The blood, being 
brought from the placenta of the mother, is thrown into 
the capfula Gliffoniana, where it is intimately blended 
with the blood in the vena portarum: then part of this 
blood goes directly into the vena cava by the duBus venofus ; 
the reft palles through the liver. Firft, then, the whole 
is fent from the vena cava into the right auricle, from 
whence part of it is fent by the foramen ovale into the left 
auricle ; the reft paffes into the right ventricle, then into 
the pulmonary artery ; then the greateft lhare it receives 
is fent immediately into the defeending aorta by the cana¬ 
lis arteriofus, and the remainder circulates through the 
lungs, and is fent back by the pulmonary veins into the 
left auricle; which, with the blood brought there by the 
foramen ovale, is fent into the left ventricle, from whence 
it is driven by the aorta through the body. The great 
defign of this mechanifm is, that the whole mafs of blood 
might not pafs through the collapfed lungs of the foetus; 
but that part of it might pafs through the foramen ovale 
and canalis arteriofus, without circulating at all through 
the lungs. 
This was the opinion that univerfally prevailed till the 
end of the laft century, wdien it was violently oppofed by 
M. Mery, who is very lingular in feveral of his opinions. 
He will not allow that the foramen ovale tranfmits blood 
from the right to the left auricle, but on rite contrary from 
the left to the right; and that for no other reafon, but be¬ 
caufe he obferved the pulmonary artery in a foetus larger 
than the aorta. Mr. Window endeavours to reconcile 
thefe two opinions, by faying the blood may pafs either 
way, and that it is here as it w'ere blended. His reafon is, 
that, on putting the heart in water, the foramen ovale 
tranfmits it any way. Mr. Rohault, profelforof anatomy 
at Turin, and formerly one of Mery’s fcholars, ftrongly 
defends his mailer, and criticifes Mr. Window. What 
he principally builds on, is the appearance this foramen 
has in fome dried preparations; but this Mr. Window will 
not allow as proof. After all, the common opinion feems 
the mod rational. 
We now come to confider the cow as a ruminant animal. 
There are no dentes inafores in the upper jaw ; but the 
gums are fomewhat hard, and the tongue rough. This 
roughnefs is occaiioned by long (harp-pointed papillae with 
which the whole fubdanceofit is covered. Tl»efe papillce 
are turned towards the throat; fo that by their means the 
food, having once got into the mouth, is not ealily pulled 
back. The animals therefore fupply the defeat of teeth 
by wrapping their tongue round a tuft of grafs ; and fo, 
prelling it againft the upper jaw, keep it ftretched, and cut 
it with the teeth of (lie under jaw ; then, without chewing, 
throw it down into the cefophagus, which in thefe crea¬ 
tures conlifts of a double row of fpiral fibres decollating 
one another. All animals which ruminate nnift have more 
ftomachs than one ; fome have two, fome three ; our pre- 
fent fubjeCt has no lefs than four. The food is carried di¬ 
rectly dow'n into the firft, which lies upon the left fide, 
and is the largeft of all; it is called yuo-ir,^ ventrkulus, and 
ytn'hicc. by way of eminence. It is what is called by the 
general name of paunch by the vulgar. There are no rugae 
upon its internal furface; but indead of thefe there are a 
vaft number of fmall blunt-pointed precedes, by which the 
whole lias a general roughnefs, and the furface is extended 
