OPH 
«d; and as there is a hole on each side, it' 
is impossible to know on which hand the 
object is situated, which you are looking 
at. 
OPERCULARIA, in botany, a genus of 
the Tetrandria Monogynia class and order. 
Essential character : flower compound ; ca- 
lyx common, one-leafed, unequally toothed, 
closed by a common receptacle, flowering 
above, seeding below, falling when ripe. 
There are three species. 
OPHIDIUM, in natural history, a genus 
of fishes of the order Apodes. Generic 
character : the head rather naked ; teeth in 
the Jaws, palate, and throat ; gill membrane 
seven-rayed ; body in the form of a sword. 
There are four species. We shall notice 
only O. barbatum, or the bearded Ophi- 
diura : this is generally about eight inches 
long, and is a native of the Adriatic and 
Mediterranean Seas. On the coasts of Pro- 
vence it is often taken with other fishes in 
nets, but by no means highly valued. It 
subsists on small fishes and crabs. 
OPHIOGLOSSUM, in botany, adder’s 
tongue, a genus of the Cryptogamia Filices 
class and order. Natural order of Filices, 
or Ferns. Generic character: capsules 
numerous, connected by a membrane into a 
distich spike, subglobular, when ripe open- 
ing transversely, without any elastie ring ; 
seeds very many, extremely minute. There 
ai'C. nine species. 
OPHIORHIZA, in botany, a genus of 
the Pentandria Monogynia class and order. 
Natural order of Stellat®. Gentianse, Jus- 
sieu. Essential character: corolla funnel- 
form ; germ bifid ; stigmas two ; fruit two- 
lobed. There are three species. 
OPHIOXYLUM, in botany, serpentine 
wood, a genus of the Polygamia Monoecia 
class and order. Natural order of Apoci- 
neae, Jussieu. Essential character: herma- 
phrodite, calyx five-cleft; corolla five-cleft, 
funnel-form ; stamens five ; pistil'one : male, 
calyx bifid ; corolla five-cleft, with a fun- 
nel-form mouth; nectary cylindric ; stamens 
two. There is but one species ; viz. O. ser- 
pentinum, scarlet-flowered ophioxylum, a 
native of the East Indies, 
OPHIRA, in botany, 3 genus of the Oc- 
tandria Monogynia class and order. Natural 
order of Onagrae, Jussieu. Essential cha- 
racter: involucre two-valved, three-flower- 
ed; corolla foiir-petalled, superior; berry 
one-celled. There is but one species ...viz. 
O. stricta, a native of Africa. 
OPH 
OPHRYS, in botany, a genus of the 
Gynandria Diandria class and order. Na- 
tural order of Orchideae. Essential cha- 
racter: nectary somewhat keeled under- 
neath. There are thirty-four species. These 
plants are of the same natural genus with 
the Orchis. Linnaeus distinguished this 
natural order into genera from the necta- 
rium, which in Orchis forms a horn or spur 
at the back of the flower, whereas the lip 
of it in this is a petal, hanging down with.a 
ridge or keel running along the back O. 
nidus avis, bird’s nest Ophrys, has the root 
composed of many strong fibres, from which 
arise two oval veined leaves, jointed at their 
base; between these spring up a naked 
stalk, about eight inches in height, termi- 
nated by a loose spike of herbaceous flowers, 
resembling gnats, composed of five petals, 
with a long bifid lip to the nectarium, a 
crest or standard above, and two wings on 
the side; capsule angular, opening in six 
parts, filled with small seeds like dust. Na- 
tive of several parts of Europe. 
OPHTHALMIA, in medicine, an inflam- 
mation of the membranes whieh invest the 
eye. 
OPIUM, in chemistry and' medicine, an 
inspissated gummy juice, which is obtained 
from the head of the “ papaper somnife- 
rum.” It is imported from Persia, Arabia, 
and other warm parts of Asia, in flat eakes 
covered with leaves to prevent their sticking 
together. It has a reddish brown colour, 
and strong peculiar smell : its taste at first 
is nauseous and bitter; but this soon be- 
comes acrid, and produces a slight warmth 
in the mouth. A peculiar substance has 
been detected in opium, to which it is sup- 
posed the properties it po.ssesses of pro- 
ducing sleep are owing. On account of 
this property this substance has received 
file name of narcotic matter. It is obtained 
from the milky juices of some plants, as 
those of the poppy, lettuce, and some 
others. Opium, which is extracted from 
the poppy, is prepared by the following 
process. The heads of the white poppv, 
which is cultivated in different countries of 
the east for this purpose, are wounded with 
a sharp instrument ; a milky juice flows out, 
which concretes, and is collected and formed 
into cakes. In this state opium is a tena- 
cious substance, of a brownish colour ; has 
a peculiar smell, and a di.sagreeable bitter 
taste. It becomes soft with a moderate 
heat. It readily takes fire, and burns rapid- 
ly, By the analysis of opium, it appears to 
