RET 
•there is nothing to do but to number the luminous and ihe 
dark parts. 
RETICULUM, one of the divisions of the stomach in 
ruminating animals, so called from the reticulated arrange¬ 
ment of the folds of its internal membrane. 
RETIERS, a town of France, department of the llle and 
Vilaine, containing, with its parish, a population of 3000; 
20 miles south-west of Vitre, and 21 south-east of Rennes. 
RE'TIFORM, adj. [ retiformis , Lat.] Having the form 
of a net.—The uveous coat and inside of the choroides are 
blackened, that the rays may not be reflected backwards to 
confound the sight; and if any be by the retiform coat re¬ 
flected, they are soon choaked in the black inside of the 
uvea* 'Ray. 
RETIMO (sometimes called Rhetzmo), a sea port of 
European Turkey, in the island of Candia, situated on the 
north coast of the island, about 40 miles west of the town of 
Candia. This town extends a considerable way along the 
shore, and has still some fortifications, but they are in decay. 
The citadel, situated on a sharp projecting rock, was built, 
as well as a fort at the other end of the town, for the protec¬ 
tion of the harbour. The latter is now in ruins, and the port 
itself so neglected, that it is now almost blocked up with sand. 
The population of Retimo amounts to about 6000, employed 
for the most part in agriculture, gardening, and the culture 
of the vine; also in making soap from olive oil. Lat. 35. 
20. N. long. 24. 21. E. 
RE'TINA, s. [Latin.] A coat or tunicle of the eye, 
formed by the expansion of the optic nerve. 
Whether the retina, or the choroides, be the principal 
organ of vision, and that on which the images of objects 
are represented, has been much controverted between 
several members of the Royal Academy; particularly 
Messrs. Mariotte, Pecquet, Perrault, Mery, and de la Hire. 
Mariotte first referred vision to the choroides, and was 
supported by Mery; the rest asserted the cause of the 
retina. 
The retina was always judged to have all the characters 
of the principal organ. It is situated in the focus of the re¬ 
fraction of the humours of the eye; and of consequence 
receives the vertices of the cones of rays, proceeding from 
the several points of objects. It is very thin, and con¬ 
sequently, very sensible. It has its origin from the optic 
nerve, and is itself wholly nervous; and it is the common 
opinion, that the nerves are the vehicles of all sensations. 
Lastly, it communicates with the substance of the brain, 
where all sensations terminate. 
As to the choroides, its use was supposed to be to stop 
the rays, which the extreme tenuity of the retina should 
let pass; and to do the same office with respect to the re¬ 
tina, which the quicksilver does to a looking-glass; espe¬ 
cially in those animals in which it is black. 
But from an experiment of a cat plunged into water, 
M. Mery conceived a different opinion. He observed 
the retina to disappear absolutely on that occasion, 
as well as all the other humours of the eye; while the 
choroides still appeared distinctly, and even with all the 
lively colours which it has in that animal. Hence, he con¬ 
cluded, that the retina was as transparent as the humours, 
but the choroides opaque; consequently the retina was 
not a proper instrument to terminate and stop the cones of 
rays, or to receive the images of objects; but that the 
light must pass through it, and could only be stopped on 
the choroides; which therefore would become the principal 
organ of vision. The black colour of the choroides in 
man is extremely favourable to this opinion ; the principal 
organ should seem to require, that the action of the light 
should terminate on it as it arrives; which it is certain it 
here does in the black, that absorbs all the rays, and re¬ 
flects none; and it should also seem necessary, that the 
action of the light should be stronger on the organ of sight 
than any where else : now it is certain that the light, be¬ 
ing received and absorbed in a black body, must excite a 
greater vibration there than any where else; and hence it is 
RET 19 
that black bodies are kindled by a burning glass much 
sooner than white ones. 
The situation of the choroides behind the retina is an¬ 
other circumstance on its side; M. Mery having observed 
the same position of the principal organ behind a mediate 
organ in the other senses, which makes an happy analogy. 
Thus the cuticle .extended over the skin is the mean organ 
of feeling; but the cutis underneath is the principal organ. 
The like is observed in the ear, nose, See. 
The retina, therefore, should seem a kind of mediate or 
secondary organ, serving to break the too strong impres¬ 
sion of the light on the choroides, or to preserve it; which 
is the use ascribed to the cuticle. Add to all this, that the 
retina is insensible, as having its origin from the medullary 
substance of the brain, which is so too; and the choroides, 
on the contrary, is very sensible, as arising from the pia 
mater, which is certainly sensible in a great degree. 
This last argument being doubted of, M. Mery was en¬ 
gaged to prove it; which he did before the Royal Academy, 
where he shewed that the optic nerve is not composed, 
like the other nerves, of fibres; that it is only a train of 
the medulla inclosed in a canal, out of which it is easily 
separable. 
We are inclined to think it probable that the choroides 
does effect an important agency in the production of our 
perception of colours. But that whatever its action may be, 
that action (or its. effects) must be transmitted to the brain 
through the retina and optic nerve seems indisputable, since 
there is no other course that it can take. 
RETINACULUM, the name of an old chirurgical in¬ 
strument used in the operation for hernia, to prevent the 
intestines from falling into the scrotum. 
RETINARIA. See Gouania. 
RETINASPHALTUM, an inflammable kind of resinous 
substance, found in Bovey coal. It was analysed by Mr. 
Hatchett, and is composed of 55 resin, 41 asphaltum, 3 
earths. 
RE'TINUE, s. [retenue, Fr.] Formerly, and accord¬ 
ing to Johnson, pronounced reti'nue. A number attending 
upon a principal person; a train. 
Not only this your all-licens’d fool. 
But other of your insolent retinue. 
Do hourly carp and quarrel. Shakspeare. 
RETINUE, Retinentia, the attendants or followers 
of a prince, or person of quality, chiefly in a journey. 
In Law, those persons are properly said to be of a noble¬ 
man’s retinue, who belong to him in quality either of servants 
(•- retainers. 
RETIRADE, in Fortification, a retrenchment made in the 
body of a bastion. 
To RETIRE, v. n. [retirer , Fr.] To retreat; to with¬ 
draw ; to go to a place of privacy. 
Thou open’st wisdom’s way, 
And giv’st access, though secret she retire. Milton 
To retreat from danger. 
From each hand with speed retir'd. 
Where erst was thickest plac’d, the angelic throng. Milton. 
To withdraw from any station. 
While you, my lord, the rural shades admire, 
And from Britannia’s public posts retire. 
Me into foreign realms my fate conveys. Addison. 
To go off from company.— Retire; the world shut out, 
thy thoughts call home. Young. —To withdraw for safety. 
—He, that had driven many out of their country, perished 
in a strange land, retiring to the Lacedemonians. 2 Mac. v. 
To RETIRE, v. a. To withdraw; to take away; to 
make to retire.—! will thence retire me to my Milan. Shak¬ 
speare. 
RETIRE, s. Retreat; recession. Not in use. 
I heard his praises in pursuit. 
But ne’er, till now, his scandal of retire. Shakspeare. 
Retirement; 
