Page:Cyclopaedia, Chambers - Volume 1.djvu/882

 GEN

ftch Analogy in the Propagation of Animals. See V

RATION.

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GEN

The III 1 * Thing, which our Difcoveries make probable, is, That Animals cannot be forrn'd of thefe Animalcula with- out the Ova in Femitlis, which are neceffary for fupplyinp them with proper Nutriment ; and this is evinced from the following Confiderations.

i° It appears, that an Animalcule cannot come for- ward, if it do not fall into a proper Nidus : This we lee in the Cicatricula in Eggs ; and tho' a Million of them mould fall into one Egg, none of them would come forward, but what were m the Center of the Cicatricula ; and perhaps the Nidus, neceffary for their Formation, is fo proportioned to their Bulk, that it can hardly contain more than one A- nimalcule ; which may be the Reafon why there are fo few Monfters. This, we fee, is abfolutely neceffary in the Ovi- parous Kinds ; and the only Difference which lies between them and the Viviparous, feems to be this, that in the lat- ter the Ova are properly nothing but the Cicatricula, with its Colliquamentum, fo that the Fcetus muft fpread forth its Roots into the Uterus, to receive its Nouriftiment ; but the Egg in Oviparous Animals may be properly termed an Uterus, in relation to the Fcetus; as it contains not only the Cicatricula, with its Amnion and Colliquamentum, which is the immediate Nouriftiment of the Fcetus but alfo the Materials which are ro be converted into that Colli- quamentum ; fo that the Fcetus fpreads forth its Roots no farther than into the White and Yolk of the Egg, from whence it derives all its Nouriftiment. Now, that an A- nimalcule cannot come forward without fome fuch proper Ni- dus, will not be deny'd; for if there were nothing needful but their being thrown into the Uterus, we do not fee why many hundreds of them ftiould not come forward at once, at leaf! while fcatter'd in fo large a Field.

i". That this Cicatricula is not originally in Utero, fcems evident from the frequent Conceptions which have been found extra Uterttm : Such as the Child which continued 16 Years in the Woman of ffholoufe's Belly : And the little Fcetus found in the Abdomen of Mad. de St. Mere, toge- ther wirh the Teflide torn, and full of clotted Blood : Such alfo feem to be the Fcetus in the Abdomen of the Woman of Copenhagen, mention'd in the Nouvclles des Lettres, for Sept. 85. All the Members of which were eafily to be felt thro' the Skin of the Belly, and which fhe had carried in her Belly for four Years: And the feven Years Gravidation related by Dr. Cole. Now, granting once the Neceffity of a proper Nidus for the Formation of an Animalcule into an Animal, thefe Obfcrvations make it probable, that the Te- ftes are the Ovaria appropriated for this Ufe : For tho' the Animalcule's coming thither in fuch Cafes, may feem to be extraordinary, and that ufually the Impregnation is in U- tero ; yet it may be collefled from hence, that the Cicatri- cula or Ova to be impregnated, are in Teflibus fmmineis; for if they were not fo, the Accidental coming of Animal- cules thither, could not make them come forward more than in any other Part of the Body; fince they cannot be forrn'd and nourifh'd without a proper Nidus.

5 U It is acknowledg'd, that the Fcetus inUtero, for fome confiderable Time after Conception, has no Connexion with the Womb; that it fits wholly loofe to it, and is perfectly a little round Egg, with the Fcetus in the midft; which fends forth its umbilical Veffels by degrees, and at laft lays hold on the Uterus. Now, from hence it feems evidenr, that the Cicatricula, which is the Fountain of the Animalcules Nouriftiment, does not fprour from the Uterus, but has its Origin clfewhere ; and falls in thither as into a fit Soil : from whence it may draw Nutriment for the Growth of the Fcetus 5 elfe it cannot be eafily imagin'd how it ftiould not have an immediate Connexion with the Uterus, from the Time of Conception.

It is indeed difficult to conceive, how thefe Eggs ftiould be impregnated per fallen maris, both becaufe there is no Connexion between the Fallopian Tubes, and the Ovary, for its Tranfmiffion ; and for that Dr. Harvey could never difcover any thing of it in Utero 1 But as to the laft, M. Lee- •wenhoeck has cleared that Difficulty by the Difcovery of in- numerable Animalcula in the Tubie, or Cornua Uteri, and thofe living a confiderable Time after Coition. And as to the former, we may either fuppofe that there is fuch an Inflation of the Tub.-e, at the Time of Coition, as makes them embrace tho Ovaries; and fuch an Approach of the Uterus and its Cornua, as that it may eafily tranfmit the Seed into the Ovary : Or elfe, that the Ova are impreg- nated by the Animalcules after they defcend into the Uterus, and not in the Ovary. The former feems probable for this Reafon, that at leaft a whole Clufter of Eggs in a Hen will be fcecundated by one Tread of the Cock : Now this Fce- cundation feems to be in the Vitellary, and not in the Ute- rus, as the Eggs pafs along from day to day : For it can hardly be fuppofed, that the Animalcules ftiould fubfift fo long, being fcatter'd loofely in the Uterut, as to wait there,

for many Days for the Foundation ef the Eggs as they pafs along The latter Conjecture has this to ftrfngthen id That the Animalcules are found to live a confidence Time, in the Uterus, and that ,f they ftiould impregnate the Ova in the Ovary it felf, the Fcetus would encreafc fo faff, that the Ova could not pafs thro' the Tuba; Uteri ; but would ei- ther burft the Ovary, or fall down into the Abdomen from the Orifices of the Tuba: And from hence probably nroceed thofe extrrordinary Conceptions in the Abdomen, out of the Uterus. See Falloi'ian Tube.

Thus much is urged for the Syftem ab Animalcule.

The Retainers to the Syftem of Generation ab Ovo, con- tend that the Rudiments of the Fcetus are laid in the Ova- ry, and that the Female furnifhes the whole Matter of the Body ; which they chiefly fupport from the Conformation in Rabbits, Sheep, Cows, Bo. where the Vagina of the Womb ' sl ° lo J n g> a >id finuous, that it is fcarce poflible the Male Seed ftiould ever arrive within the Body of the Uterus ; Specially in Cows, whofe Vagina is fill'd with a thick, vifcid ■ Ichor, and the inner Orifice of the Womb exactly clokd : Befide that, the Thicknefs of the Membranes of the Ova fhould feem impenetrable to fo craft aMatter as the Male Saed. Add, that if Animalcula be found in the Male Seed, whichj however, will admit of fome Difpute (that interline Motion and Agitation of the groffer Particles thereof, which give rile to the Opinion being accountable for from the common' Laws of warm Fluids) yet are the fame obferv'd in Vinegar, Pepper, Water, &c. Add, that it is highly improbable, thofe Animalcules fhould contain the Rudiments of a future Body i, fince their large Numbers would produce too plentiful an Offspring ;inlomuch that it would be neceffary for 9999 Parts of them to be in vain, and perifli : Which is contrary to ths Oeconomyof Nature in other Things.

Analogy is likewife urged in favour of this Syftem: Thus 5 , all Plants are maintained to arife from Eggs ; Seeds being no other than Eggs under another Denomination. All Ovipar- ous Animals do unexceptionably arife from Eggs, which the Female cafts forth ; and 'tis highly probable, that the Vi- viparous only differ from Oviparous, in that the Females lay and hatch their Eggs within themfelves. See Vivi- en arous, and Oviparous.

Againft this Hypothefis it is urged, that what are lifuatlf called Ova, or Eggs, in Women, are no other than little Cells, or Bladders, full of a certain Liquor : And how can a Drop of Liquor pafs for an Egg? Add, that thefe ima- ginary Eggs have no proper Membrane belonging to them; nor any Covering but that of the Cellj which fcems fo in- feparable therefrom, that when they are difcharged, it is hard to conceive how they ftiould take it with them. And be- fide, how fhould they make themfelves a Paffage through the commom Membrane wherewith the Ovary is inverted* which is of fo clofe a Texture, that it muft feem abfolutely impenetrable by a round Body of fo Toft a Confiftence, as one of thefe Veficles. Laftly, Veficula:, in all refpeSs per- fectly like Ova, have been found in other Parts of the Body, where it is apparent they could not ferve for any purpofes of Generation. Mem. del Acad. Royal des Scien, An. 1 708, 1 709.

To this it is anfwer'd, that Ova or Veficula: have been actu- ally found in Diffeffions, detach'd and feparated from the Ovary, and the Ruptures in the Membrane of the Ovary, thro" which they had pafs'd, ftill vifible. M. Littrc even ob- ferved fome of thefe feparated Ova fpread with Blood Vef- fels, like thofe in the Yolks of Birds Eggs. Nay more, the fame Author is pofitive, that he faw an Embryo in one of the Ova not yet feparated; could difcern its Head, Mouth, Nofe, Trunk, and Funiculus Umbilicalis, whereby it ad- hered ro the Membranes of the Ovary. See Embryo. But this will come to be further confider'd under Genera- tion of Man.

Sir John Floyer ftarts a Difficulty, which feems to prefs equally againft each Syftem, taken fingly : 'Tis fetch 'd from Monfters : In a Mule, for inftance, which is the Production of a Venereal Copula between an Afs, and a Mare, the Bulk of the Body partakes of the Form of the Dam; and the Feet, Tail, and Ears of that of the Sire : Hence it is argued, that the Rudiments of the greater Part of the Fcetus are laid in the Ovum ; and that the Inpregnation either conveys, or changes the Extremities. If the Male fup- plied the Animalcula, 'the Fcetus ftiould always be of the fame Species as the Male: If the Female fupply it, it ftiould be of her kind ; whereas Monfters are of both. See Mon- ster.

Generation of Man i As 'tis in human Subjects, that the gradual Procefs of Generation has been principally in- quired into; and the Structure, and Office of the Organs fubfervient thereto, chiefly examined : What the lateft Na- turalifts, and Anatomifts have fettled with regard thereto, is referved for this Head.

The Tarts of Generation, then, are different in ihe dif- ferent Sexes.

Thofe, proper to the Male, are the 'Penis ; the Tefticles ; the Vejiculie Seminales; the Vnfa ieftrtrai»; «be 2>arajla-