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The chorion, that most simple yet most 
perfect temporary substitute for tlie lungs, 
if examined in the latter half of incubation 
in an egg very cautiously opened, presents, 
without any artificial injection, one of the 
most splendid spectacles that occurs in the 
whole organic creation. It exhibits a sur- 
face covered with numberless ramifications 
of arterial and venous vessels. The latter 
are of the bright scarlet colour, as they are 
carrying oxygenated blood to the chick ; 
the arteries on the contrary are of the deep 
or livid red, and bring the carbonated blood 
from the body of the animal. Their trunks 
are connected with the iliac vessels ; and, 
on account of the thinness of their coats, 
they afford the best microscopical object for 
demonstrating the circulation in a warm- 
blooded animal. 
The other membrane, the membrana vi- 
telli, is also connected to the body of the 
chick ; but by a twofold union, and in a 
very different manner from the former. It 
is joined to the small intestine, by means of 
the ductus vitello-intestinalis (pedunculus, 
apophysis) ; and also by tlie blood-vessels, 
wliich have been already mentioned with 
the mesenteric artery and vena porta;. 
In the course of the incubation the yolk 
becomes constantly thinner and paler by 
the admixture of the inner white. At the 
same time innumerable fringe-like vessels 
with flocculent extremities of a most singu- 
lar and unexampled structure, form on the 
inner surface of the yolk-bag, opposite to 
the yellow ramified marks above-mention- 
ed, and hang into the yolk. There can be 
no doubt that they have the office of ab- 
sorbing the yolk, and conveying it into the 
veins of the yolk-bag, where it is assimilated 
to the blood, and applied to the nutrition of 
the chick. Thus in the chicken, which has 
just quitted the egg, there is only a re- 
mainder of the yolk and its bag to be disco- 
vered in the abdomen. These are com- 
pletely removed in the following weeks, so 
that the only remaining trace is a kind of 
cicatrix on the surface of the intestine. 
Comparative degree, among gramma- 
rians, that between the positive and super- 
lative degrees, expressing any particular 
quality above or beneath the level of ano- 
ther. 
COMPARISON of ideas, among logi- 
cians, that operation of the mind whereby 
it compai'es its ideas one with another, in 
regard of extent, degree, time, place, or 
any other circumstance, and is the ground 
of relations. This i$ a faculty which the 
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brutes seem not to have in any great de- 
gree. 
Comparison, in rhetoric, a figure that 
illustrates and sets off one thing, by resem- 
bling and comparing it with another, to 
which it bears a manifest relation and re- 
semblance, as the following figure in Shak- 
speare ; 
“ She never told her love. 
But let concealment, like a worm i’ the 
bud. 
Feed on her damask cheek : she pined 
in thought. 
And sat like Patience on a monument, 
Smiling at Grief.” 
COMPARTMENT, or Comparti- 
ment, in general, is a design composed of 
several different figures, disposed with sym- 
metry, to adorn a parterre, a ceiling, &c. 
A compartment of tiles, or bricks, is an ar- 
rangement of them, of different colours and 
varnished, for the decoration of a building. 
Compartments, in gardening, are an assem- 
blage of beds, plats, borders, walks, &c. 
disposed in the most advantageous manner 
that the ground will admit of. Compart- 
ments, in heraldry, are otherwise called 
partitions. 
COMPASS, or mariner's compass, an in- 
strument whereby the ship's course is de- 
termined. See Magnetism. 
Compass is also an instrument in survey- 
ing ot land, dialling, &c.' whose structure is 
chiefly the same with that of the mai-iner’s 
compass 5 and, like that, consists of a box 
and needle ; the principal difference being 
this, that instead of the needle’s being fitted 
into the card, and playing with it on a pi- 
vot, it here plays alone. See Surveying. 
Compass dials are small horizontal dials, 
fitted in brass or silver boxes for the pocket, 
to show the hour of the day, by the direc- 
tion of a needle, that indicates how to place 
them right, by turning the dial about till 
the cock or style stand directly over the 
needle and point to the northward ; but 
tliese can never be very exact, because of 
the variations of the needle itself. 
Compasses, or pair of compasses, a ma- 
thematical instrument for describing circles 
measuring figures, &c. They consist of two 
sharp.pointed branches or legs of iron, 
steel, brass, or other metal, joined at top 
by a rivet, whereon they move as on a 
centre. 
Compasses of three legs are, setting aside 
the excess of a leg, of the same structure 
with the common ones •, their use being to 
