OBT 
other aerige of dropfy ; and the occurrence of all large 
tumours in the vifcera, which, by preffure upon the conti- 
guous an 8, oe and derange their action. All 
chronic enlargements of the glands and other parts tend, by 
fuch preffure, to obftru& the proper circulation and excre- 
tion of the fluids, and therefore to produce various fecondary 
or fymptomatic difeafes. Thus f{cirrhous tumours of the 
mefentery, pancreas, or of the liver itfelf, by prefling upon 
the vena porte, or great veflel of the liver, are liable to pro- 
duce dropfy of the belly, in confequence of impeding the 
circulation of the blood through the veffels of the abdomen, 
which therefore pour out the ‘thinner or watery part of the 
blood into the cavity of the belly, from their exhalent extre- 
mities. The fame tumours, if they prefs upon the bile- 
ducts, will impede the flow of the bile into the inteftines, 
and occafion jaundice. i i 
of the lungs, heart, kidnies, brain, an ery 
of the body, are derange by obftruCtions, occurring within 
their | own fubftance, or in the adjoining parts. 
obftruGtions are feated in organs of various ftructure, 
and confit of difeafed changes of various nature, the proper 
treatment of the difeafes which they produce, can only be 
directed with fuccefs, after a careful and filful inveftigation 
them. 
ms, with certain organic derange- 
ments of the internal pats is learnt by an obfervation of the 
f any partic 
remedy, as a deobftruent, iy be often altogether ufelefs, 
and not unfrequently injurio 
The various difeafes, pean from obftruction, will 
be found under ti = heads. See Droprsy, JAun- 
pice, MarasMu 
OBSTRUENTS.. " See DrossrRuEnT. 
U 
° The opening is called the 
obturator foramen; the ligament which occupies it, an 
aint a vein, a nerve, and two mufcles, have the fame 
thet. 
The obturator externus ({ous- pubo-trochanterien etal 
is a mufcle of a tri eee ar figure, fituated at and 
igh, and ex Beer oon the rane 
y a tendon to the lower 
part of the internal furface of the great trochanter, adhering 
firmly to the orbicular ligament. It is covered in front by 
the petinalis, the adductors, and the quadratus. The upper 
edge is rather concave, and extends obliquely from within 
outwards, and from above downwards, from the pubes to 
the great trechanter : the obturator veffels and nerve come 
over it towards the infide, and it is connected, on the outfide, 
OB Y 
by cellular tiffue, to the orbicular ee The inferior 
margin is nearly tranfverfe in its direGion. The pofterior 
urface covers the obturator Geom and a part of the 
one. 
This mufcle is flefhy at its origin, and in moft of its — 
{tance ; but its attachment to the trochanter is tendinou 
It rotates the greene outwards, and draws it foes 
the oppofite lim 
The internal fitiace of this uc is cavers by the le- 
vator ani, and the pudendal veffels; the external covers the 
obturator ligament, and a part of the aoa —— the 
outfide of the pelvis, the tendon lies upon the ifchium and 
= i -joint, with the gemelli more or lefs clotely aaa 
° An interval is left between two portions of the mufcle, 
at its origin, and gives paflage to the obturator veffels and 
nerve. 
The origin is flefhy, and comparatively broad ; the mufcle 
has become narrow where it turns round the ifchium, and it 
is ftill narrower on the outfide of the pelvis, where it is al- 
moft entirely tendinous. A very well-marked burfa mucofa 
covers the tendon and bone, where the former turns over the 
From the fharp turn which 
the an makes over the bone at this part, the rubbing in 
its ation muft be very confiderable: we find the bone here 
marked - feveral rf correfponding to divifions in the 
tendon. 
The obturator externus rotates the thigh-bone outwards : 
when the hip is bent, it will feparate the thigh from the op- 
pofite limb. 
OBTUSE literally i imports blunt, dull, &c. in oppofition 
to acute, fharp, brifk, &c. 
~ OstusE Angle, in Geometry. See A 
Oxtuse-Angled Triangle, isa cane or one eat whofe angles 
is obtufe. 
Ostuse-Angular Section of a Cone, a name given to the 
hyperbola by ancient geometricians, becaufe they confidered 
it only in fuch a cone, whofe fection by the axis is a triangle, 
oo at the vertex. See Cowic Seéfions, and Hy- 
BOLA. 
2) 
B 
Ouie Apput. See Apput. 
OBVA, in Gesgraphys a river of Ruffia, which runs inte 
the Kama, near Obvin 
OBVENTIONS, Geernes in Ancient Law Bo aks, 
fignify the produce of a benefice, or fpiritual ving 5 in- 
cluding oblations, tithes, rents, and o 
OBVINSK, in Geography atown of ees in ‘the go= 
vernment of Perm ma; 60 miles N. of Perm. 
‘se 
e largeft river in the Ruffian empire, 
euleeaae to its name, which fignifies «* Great,”’ originates 
Qq properly 
