Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/171

 OVA

cundine; and in the child itfelf, the face at this time began to be formed, and the features were diftinguifhable, and the prin- cipal parts of the body eafily traced. At longer periods from the time of impregnation, the features and lineaments of all the parts appear more and more ftrong; and the author has given accurate defcriptions of the progrefs of the fcetus to- ward perfection, and figures of it at three, four, five, and fix weeks after conception, at which lafl: time all is very fair and plain.

The ova in which thefe lineaments of th - fcetus are found af- ter conception, are themfelvcs formed without fuch lineaments, not only in married women, but in maids who have had no commerce with men at all ; and it is the fame in creatures na- turally oviparous. The pullet will even lay her eggs without any intercourfe with the cock, but then they will have none of the lineaments of the young fowl, which are found in the eggs laid after treading, and enlarging every day after the beginning of the incubation.

The eggs found in the tefticles of unmarried women are gene- rally of the fize of a pea, round, and containing a glutinous liquor, which will harden, on boiling, in the fame manner as the yolk and white of a common egg. The tafte is rather un- pleafant than infipid, and they are inveloped in two (kins, which after they are fallen into the womb become two mem- branes, called the amnion and chorion, which enlarge as the contents enlarge.

Fallopius obferved thefe eggs in women before the time of Kerkring, but it was this author who carried on the conjec- tures of the other into a fort of certainty, and added proofs to what he had firft hinted from a number of experiments; and Wharton, in his account of human generation, is of opinion, that the femen penetrates into the teftes of thefemale by means of the Fallopian tubes ; in which cafe, the impregnation is in this inftance performed exactly as in others of the oviparous creatures, and the whole difference amounts to no more than this, that in fome the impregnated matter lofes its figure of the egg before it is excluded the parent; but in others, it re- tains it till it is not only put forth out of the body, but hatch- ed by its genial heat afterwards.

The egg being impregnated by the femen admitted this way, defcends into the womb, and there becomes, in a few days, of the biggnefs of a cherry ; and afterwards increafes, as we have already obferved. This author having an opportunity of opening the body of a woman who had died fuddenly about four days after the end of one of the menftrual dif- charges, found in the womb an egg, of the biggnefs of a black cherry : he afked the husband carefully, whether he had lain with his wife fince the time of the menfes ; and was in- formed that he had. This egg was evidently the produce of that impregnation ; and tho', at the utmoft, it could be no more than four days old, the fcetus was plainly diftin- guifhable in it, on an accurate infpe&ion ; and the head in fome fort found : the reft of the body feemed an unformed mafs of flefh. In fuch another cafe, where there was reafon to believe the embryo about fifteen days old, the eyes, nofc, ears, and mouth, were eafily diftinguiftiable in the head ; and the body was fo far fafhioned, as to be eafily known by its flupe, and the rudiments of legs and arms appeared very plainly from it. The bones, as they are afterwards to be- come, are at thefe young periods mere griftles, and harden by degrees afterwards ; but they foon acquire that degree of firmnefs, that the Heft may be taken off and they preferved as fkeletons.

At about three weeks from the time of the conception, the

fcetus has its cartilages for bones fo perfeft and fo firm, that with due care in the management of fo tender an object, the

flefh may be feparated, and a fkeleton preferved of this final!

t \ The head is very large at this period, in proportion to the body ; but what is afterwards to become the Ikull, is only a membrane inflated with wind. The arms and hands are feen diftinftly, and even all the fingers are formed. The number of the ribs may be eafily counted, and the toes are as diftmfl as the fingers; but they are all fo minute and tender, that a very nice hand, and very great art are ne- ■ ceffary for the difplaying them. After another week, that is, when the fcetus is a month old, the bones are fo well formed, that the whole figure preferves its form, and is able to lupport itfelf. The jaw bones appear; the clavicles are formed ; and all the ribs are very fair and diftma, except the hrft and lafl ; and thefe two, even after another month, do not acquire the conhftence of bones.' At this period of one month, the joints of the arms, and thofe of the Ws are all very diftinflly feen. °

On examining a fcetus at two weeks beyond this period, that is, at fix weeks from the time of conception, the inferior jaw bone has in it fomewhat very remarkable; for it is plain- ly feen to be compofed of fix little bones ; whereas, in the younger periods this is not obfervable; and when the child is born they are all joined together, and make but one bone. I hefe are the proportions of growth in foetus's, which have continued regularly growing to the time of the death of the parent, and have been taken out by diflbaion afterwards: much lefs is to be judged from abortions, where the re- gular procefs of nature in the growth and formation of the

Suppl. Vol. II.

OVA

fcetus is perverted, and the child has, perhaps, been dead fome months before it is excluded, or has been fickly, and therefore not capable of taking nourifhment, and growing as it mould have done. For thefe reafons it not unfrequently happens, that an abortive fcetus of four months is not larger than one of thefe regular foetus's of fix or eight weeks ; nor the parts anything more advanced in their (rate and folidity, or if at all, but very imperfeaiy and irregularly. Mr. Dennys has added fome obfervatious on this fyftem of Kerkring ; he agrees that thefe egjs, in which the rudiments of the fcetus are firft to be difcerned, are generated in the tefticles of the female, and made to defend thence by the fpintous effea of the male-femen, making its way thither thro' the tubes ; and adds, that they are of very different forms and fizes in different women The fame woman often has, in her tefticles, eggs of very different fizes ; and as to the proportion in fize, between different animals, no regard feems paid in it to their bulk, fince not only thofe of a cow, are much fmaller than thofe of a woman, but thofe of a duck, or a hen, are vaftly larger than either. The firft beginnings of things do not always bear a proportion to their ftate and increafe, in the animal or vegetable world : beans are a much larger feed than that of the apple or pear, tho' the latter raifes a large tree, while the former only furnifhes a fmall plant. The reafon why the eggs of fowls are pro- portionably larger than thofe of the human fpecies, or of quadrupeds, is, that they are to contain not only the yountr animal, but alfo the food for it to live on in the firft part of its life, Dennys, in Keikring, de Ovo. Monfieur Gaulois obferves, that the veficles or eggs, in all forts of females, are to be obferved in three forts of ftate or condition : Firft, while they are fattened to the place where nature has'lo iged them, as in a repofitory. Secondly, when they are loofened from the place. And Thirdly, when they inclofe the embryo

In the firft of thefe ftates, they are common to all females in the animal world ; and authors of long ftanding have ob- ferved, that there were in all the female animals, veficles faftened to certain parts of their bodies It is alfo certain, that after conception, that which inclofes the fcetus is very like an egg; but this is no new doflrine neither, for even Hippocrates and Ariftotle have advanced it: Harvey alfo, of later times, has treated very much at large on this fubjea. The whole matter, in the doarine of Kerkring that is new, and that deferves a further enquiry is, whefher'thefe veficles, which were always known to be faftened to the bodies of females, are at all loofened from them; and whether that kind of egg, wherein the embryo is found, be, or be not one of thefe veficles loofened ?

The fyftem of Kerkring is founded on the anfwering this queftion in the affirmative; but thofe who are of the con- trary opinion, who are not a few, think, that the bladder refembling an egg, in which the fcetus is formed, comes not from elfewhere, but is formed in the place of the con- ception ; and Haney pretends to explain in what manner it is formed there ; and they all agree, that the veficles, called eggs in females, are fo faftened that they never can he removed ; and even if they were, that there is no paf- fage large enough for them to defcend by from the place of their formation into the womb. Some pretend alfo, that if thefe are eggs then men have eggs alfo ; for that the ve- ficles found in clufters at the fides of the vafa deferentia, which anatomifts from their figure compare to a duller of grapes, are truly and exaaiy of the fame kind with thofe veficles called eggs in females. See Eggs. Ova, among the antients, a kind of verfes, wherein the ver-

fes were reduced to the form of an egg. Hofm. in voc, OVAL-teaf, among botanifts. See Leaf. Foramen OVALE. See Foramen Ovale. OVARY, ovarium (Cyct.)— Ovarium offifhes. All fifli have wjaria, but they, as well as the eggs they contain, differ great- ly in the different kinds, in number, fituation, figure, and ftruaure. In the cetaceous, the cartilaginous, and moft of the other kinds of fifti, the ovarium is double, or there are two eva-ia ; but in fome fifh, as in the ofmarui, the pe'ea fiuviatilis of Bellonius, and perhaps in fome ethers it is finale. Ai to its fituation, it generally occupies the whole length of the abdomen, as in moft of the fpinofe fifties ; and in the petromyz.um and accipenfer. In many of the cartilaginous fifties it occupies only the upper part of the abdomen ; and finally, in the cetaceous fifties it is placed at the corner of the uterus. As to its figure, it is generally oblong and com- preffed, as is feen in moft of the fpinofe kinds : in thofe fifh which have it fingle, it is oblong and cylindric, and in the cetaceous fifties it is round.

The eggs themfelves are alfo very different in number and ftruaure. In regard to number, they are in fome fifties very few, as in the cetaceous kind*. In the cartilaginous kinds they are fomewhat more numerous, amounting to fifty or a hundred ; and in other kinds of fifti they are fo numerous, as to be beyond account.

In regard to their fize and ftruaure, they alfo differ con-

fiderably : in fome fifti they are large, and refemble a hen's

egg in their contents ; having a white, and yelk, and cica-

Q_ q tricula,