dangerous in the firft three months; but a frequent habit 
of mifcarriage debilitates the fyftern, thatters theconftitu- 
tion, and lays the foundation of chronic difeafes of the 
1110ft obftinate and dangerous nature. In the advanced 
months, the prognofis will be'more or lefs favourable, ac¬ 
cording to the patient’s former ftate of health. The prox¬ 
imate caufe of abortion is the fame with that of real tra¬ 
vail,- namely, a contradling effort of the uterus, and abdo¬ 
minal mufdes, aflifted by the other expulfive powers. The 
remote caufes cannot be explained with precifion, as many 
circumftances, with regard to the nature of impregnation 
and connection of the foetus with the placenta and uterus, 
are fubjedts involved in many difficulties ; fo that the ge¬ 
neral maxims which follow, are the heads that require 
particular attention, i. Whatever interrupts the regular 
circulation between the uterus and placenta. 2. Every 
thing that excites the fpafmodic contradlion of the uterus, 
or'other aflifting powers. 3. All accidents, or occafions, 
that deprive the foetus of life. 
In confequence of the great abridgment of the human 
race by abortion, and of the ill health it induces to thofe 
unfortunate females who become fubjedl to it, the late Dr. 
Hunter bellowed infinite pdins to inveftigate its caufe, and 
to check i|ts progrefs. He diflefted three abortions, which 
happened at the mod ufual time women are fubjeft to this 
'misfortune, namely, toward the end of the third month ; 
'whence it appeared that there is an extindtion of life in the 
foetus for fome time before any fymptoms of abortion oc¬ 
cur. For inftance, if the mifcarriage happens about the 
end of the third month, the age of the foetus is generally 
no more than eight or nine weeks; or if it perifhes in the 
fifth, fixth, or feventh, month, it will ft ill be retained in 
the uterus, and the expulfion will rarely happen until near 
the completion of its full time. 
Previous to opening thefe abortions, Dr. Hunter had 
made feveral ufeful difcoveries relative to the human preg¬ 
nant uterus, which fee under Anatomy. His brother, 
Mr. John Hunter, had likewife, by a number of furgical 
operations, manifefted, that “ the blood is the life of the 
body;” which fee under Blood. Hence Dr. Hunter 
concluded, that a careful inveftigation of the minuter vef- 
iels of the uterine fyftern, with their ramifications, would 
be the likeiieft means of obtaining fatisfafilory information 
on this delicate fubjedf. This alfo led him to the diicovery 
of the Decidua, which is a membrane of a very peculiar 
nature, the knowledge of which throws great light upon 
the contents of the pregnant womb, and upon the connec¬ 
tion between the mother and child. It appears to be an 
efflorefcence of the internal coat of the uterus; and is 
therefore (lied, as often as a Woman bears a child, or fuf- 
fers, a mifcarriage. Itconfiftsof two parts, called decidua 
veira, and decidua rejlexa. In feparating it from the chorion, 
and from the mu'fcular fibres of the uterus, an infinite 
number of fmall veins and arteries are difeovered full of 
blood, which ramify from its outer furface inwards through 
its whole fubftance, blending itfelf infeparably with the 
umbilical portion of the placenta. Its principal arteries 
run in winding convolutions, like the coilings of a fnake ; 
forming an appearance much refembling that of lace; ■ and 
confidering the number and fize of the veflels, which are 
neceflarily broken upon the expulfion of the foetus, we 
cannot longer wonder at thofe frequent fatal bleedings, 
which accompany mifcarriages in an advanced ftate of 
pregnancy. The fubjedts of thefe curious and mafterly 
difletlions are reprelented on the annexed plate,-of which 
the. following is an explanation. 
Fig. 1. An abortion of about nine weeks old, feen on 
that fide which is membranous. The decidua is torn, and 
turned fomewhat alide, to (hew the fmooth and opaque de¬ 
cidua reflexa. A, the rough external furface of the deci¬ 
dua, which exfoliated from the womb. B, the outlide of 
a fmall portion of the placenta, the reft of which was fitu- 
ated on the back part of this objeft. CC, the internal 
cribiform furface of the decidua, which, in the firft months 
of pregnancy, does not adhere to the membranes which it 
ABO 
enclofes. DD, the lacerated edge of the decidua which 
had been continued into the edge EE of the fame 
membrane. F, the decidua reflexa fipread over the out- 
fide of the chorion. GG, the angle of reflection at the 
edge of the placenta, where the inner layer of the decidua 
is turned over the chorion ; much in the fame manner as 
the inner lamella of the pericardium is reflected, to cover 
the outer furface of the heart. H, the termination of the 
decidua at the cervix uteri. 
Fig. 2. (hews a vertical fedtion of the fame fubject. 
AA, the fedtion of the placenta; which, wemuftfuppole, 
had adhered to the upper and back part of the womb. B, 
the fedtion of the anterior portion of the decidua. C, the 
fedtion of the pofterior portion of the decidua. D, the ter¬ 
mination of the decidua at the cervix uteri. E, the cavity 
of the amnion, in which the embryo hangs by a (lender 
navel-ftring, from the infide of the placenta. F, the fec- 
tion of the three membranes, which are not only conti¬ 
guous, but adhere to one another, viz. the amnion, the 
chorion, and the decidua reflexa. GG, the angle at the 
edge of the placenta where the inner layer of the decidua 
is refledted over the outfide of the chorion. H, here thofe 
three membranes are a little feparated, to (hew their courle 
at the placenta. 
Fig. 3. reprefents an abortion of about eight weeks old. 
A (mail ftrap of the decidua is cut out, and turned up, to 
(hew the cavity between it and the other membranes. A, 
the cut flip of the decidua. B, the part of the concep¬ 
tion where there is no decidua, viz. oppofite to the paiTage 
through the cervix uteri. CC, the external furface of the 
decidua. D, the decidua reflexa covering the chorion 
and amnion, which projedt and fill up the cavity of the 
decidua. E, the outlide of the upper part of the pla¬ 
centa. 
Fig. 4. reprefents the fame fubject, when the decidua 
had been opened by a crucial incifion, and the four angles 
had been turned oft’, and then a round piece of the deci¬ 
dua reflexa diffedted off, and turned to one fide, to (hew 
the loofe veflels on the outlide of the chorion. AA, the 
infide of the four angles or flaps into which the decidua 
was reduced by a crucial incifion. BB, the decidua re¬ 
flexa covering the other membranes. C, the angle at the 
edge of the placenta where the interior lamella of the de¬ 
cidua is continued over the outlide of the chorion, forming 
the decidua reflexa. D, a round portion of the decidua 
reflexa dilfedfed from the outfide of the chorion and turn¬ 
ed afide. E, the chorion, with itsfhaggy veflels, laid bare. 
Thefe veflels adhered firmly to the decidua reflexa, and 
parts of them were cut off with, that membrane. 
Fig. 5. (hews an abortion of the fame age,- confiding of 
the chorion only, with its veflels and contents; that is, 
without the .decidua, or uterine part of the fecundines. 
A, the larger and more crouded branches of the (baggy 
veflels which (hoot from the external furface of one part 
of the chorion, to mix with the decidua, or uterine part, 
to form the placenta. B, that portion of the chorion which 
afterwards becomes the uniform tranfparent membrane. 
It is covered with fewer and more delicate floating veflels, 
which lofe themfelves in the decidua reflexa. The em¬ 
bryo is feen through it. C, the velicula umbilicalis on the 
outfide of the amnion, feen through the chorion; with a 
whitifh thread, (the remains of an artery and vein,) lead¬ 
ing from it, towards the navel of the embryo. 
Fig. 6. reprefents the fame abortion opened. The mem¬ 
branes, which were at the fore-part, being cut from the 
placenta, and turned- up, the embryo is diftindtly feen. 
A, the veficula umbilicalis, from which B, the remains 
of an artery and vein, in the form of a white thread, 
pafs to C, the navel of the embryo, with fome turns of 
the inteftines lodged in the beginning of the navel-ftring. 
The common caufes of abortion are, the death of the 
child; weaknefs or relaxation of the mother; or too great 
evacuations. It however proceeds oftener from a violent 
diftention, or rupture, of the minuter veflels of the uterine 
iyftern, occafioned by too ftrong exercife; railing, great 
