[7] INTRODUCTIO.

INTRODUCTION

Quamquam jam antea eorum fere omnium, qui de incubatis ovis aliquid literis mandaverunt, ut in enarrandis factis ingens discrepantia, ita mirificus consensus in enumerandis hujus disquisitionis difficultatibus nos curiosos reddiderant; tamen brevi {tempora} <tempore> nostra ipsorum experientia satis superque nos docuit, quanta soleat natura iis, qui ejus interiorem in officinam penetrare conantur, impedimenta objicere, quantis praesertim nebulis dicam an tenebris? suum in animantibus procreandis artificium offundere et velare consueverit. Nihil igitur antiquius habendum decrevimus, quam, magna ovorum copia adhibenda, eorum diversis temporibus diverso statu qua possemus maxima cum subtilitate inspiciendo et sub censuram vocando eo anniti, ut primum crebra omnium observationum repetitione [8] in contemplandis naturae miraculis magis magisque adsuesceremus; deinde ut ne minima minimo quidem temporis momento facta in foetu immutatio aciem nostram falleret aut effugeret; postremo autem, ut, si quid veri dignoscere visi nobis essemus, similium experimentorum cumulo a dubitatione ad veritatem adduceremur, vel ab omni errore, ex festinatione forsitan orto, revocaremur.

Even if already previously made me curious not only the enormous discrepancy in expounding the facts, but also the extraordinary approval in listing the difficulties of this treatise of almost all those people that wrote something about the incubated eggs, nevertheless in a short time the experience we have done of them has shown us sufficiently and as an extra how many impediments the nature is usual to oppose to those people who try to penetrate in its most intimate laboratory; furthermore, with how many clouds or shadows, I should say, it has been usual to darken and to dim its clever technique in producing living beings? Therefore I decided to have to consider nothing more important of the fact, by employing a great amount of eggs, by examining with the greatest depth allowed to us their condition in different moments, and submitting it to a rigorous screening, to strain us in first place by availing us on the frequent repetition of all the observations, to get more always used to the contemplation of all the prodigies of nature; in second place to do so that not even the least change, happened in the embryo in a very brief instant, was deceiving or avoiding our watchful attention; finally then so that, if it seemed us to detect some truth, we were driven from the doubt to the truth thanks to the sum of the similar experiments, or at least we were distracted from any type of error, probably risen because of the hurry.

Ad haec omnia exsequenda jam non a gallinis ova incubanda, sed illius machinae ope fovenda curavimus, quae ab Hollmannio[1] inventa, a Blumenbachio divulgata est et collaudata. Hoc igitur apparatu usi, eodem tempore ad quadraginta ova temperare potuimus. Si quis autem contra hujus machinae usum moneat, quod contramoneri possit, non aptam esse eam ad temporis momenta accurate denotanda; ei obsistit hoc, quod tantum non omnes, qui in incubatorum ovorum naturam inquisiverunt, in eo consentiunt, quod a gallinis ipsis incubita ova tempore maxime dispari animari dicant. Ceterum pulli, qui, usque dum excluderentur, in machina relicti erant, constanter vigesimo primo quoque die in lucem sunt editi.

To do all these operations we have not made the eggs brooded by hens, but we incubated them with the help of that equipment invented by Hollmann and spread and tested by Johann Friedrich Blumenbach*. Then, by using this equipment, we have been able to keep about forty eggs at constant temperature. But if someone intended to criticize the use of this equipment, since that a criticism can be advanced because it is not proper in pointing out with precision the times of the execution, it can be objected to him that nearly all those people that devoted their researches to nature of the incubated eggs, are almost all agreeing on the fact to say that just the incubated eggs by the hens in general take life in very different moments. On the other hand the chicks, left in the equipment until the moment of the exit from the egg, regularly came to the light at twenty first day.

[9] Ceterum observavimus, incubatui infra 28° R. et supra 32° R. locum non esse; tum singulorum momentorum, quae in omni harum mutationum serie deprehenduntur, celerius tardiusve subsequentium causam non in majori minorive caloris gradu, sed in ipsorum ovorum natura et conditione positam esse; deinde quo recentiora ova adposita sint, eo certius evolutionem succedere.

Then we observed that the brooding was not possible below 28 and above 32 Réaumur* degrees (<35 and 40 Celsius degrees>); furthermore, that the cause of the single movements, felt in any order of these mutations, and happening as soon as possible or more later, must be sought not in the greater or lesser degree of heat, but in the nature and in the condition of the eggs; in second place, how much more recent is the laying of the eggs, so much more sure is their evolution.

Hac, quam demonstravimus, via etsi amplius duorum millium ovorum commutationcs observavimus, recensuimus, perscrutati sumus; tamen persuasum nobis est, ne hanc quidem experimentorum abundantiam ad eam nobis rei cognitionem parandam, quam re vera paravit, suffecisse, nisi jucunda illa studiorum nostrorum conjunctio acccssisset. Cum enim nihil omnino pro certo ratoque haberemus, quin unusquisque nostrum idem saepe esset eodem modo expertus, cognovisset idem, idem evidentissime sibi ipse probasset: singula experimenta, quae enarravimus, ut quasi tergemina ducenda sunt, ita unius anni et quod excurrit, qui in hanc disquisitionem impensus iabor est, quasi integrum triennium exhaustum [10] dicendum est.

With the demonstration we have given of this, although our observation, our examination, our evaluation are extended to the changes occurred in more than two thousand eggs, nevertheless the conviction is formed in us that neither this abundance of experiments would have been enough to give us the knowledge of the phenomenon, that actually was brought to us, unless there had been a welcome addition, the well-known communality of our studies.  Since in fact we didn't have the absolute certainty that everyone of us had often carried out in the same way the same experimentation, had gotten the same knowledge, had reached with the greatest evidence the same personal demonstration: as the single experiments, that we have commented, have to be considered, so to say, triplex for affinity, so we have to inform that for them the time of one year has been employed and almost the whole following triennium, a labour that was not indifferent to the goals of this search.

Prae ceteris autem maxima ad hujusmodi studia e quotidianis colloquiis redundare commoda intelleximus. Familiarium enim sermonum nostrorum beneficio accidit, ut aut subito deprehenderemus, an omnes pari modo de facto aliquo et loqueremur et sentiremus, aut errores cito eorumque sedes apparerent, aut tandem in novam aliquam observandi discendique viam incideremus et quasi conjunctis viribus ad veritatem adspiraremus. Illud ipsum, quod hinc inde nostrum alius aliud in iisdem studiis quaereret; unus rerum claram et distinctam notionem vel exemplar potius, quod possit arte sua reddere; alter anatomicarum quarundam et physiologicarum idearum vel approbationem, vel repetitionem; tertius denique eventum qualemcunque secure et sine omni praeoccupationis cupiditate exspectaret: haec ipsa, inquam, consiliorum nostrorum diversitas magnum nobis attulit adjumentum. Nemini enim nostrum justo citius progredi licuit, neque unquam praeceptis caruimus, quae in ipsa investigatione constituenda sequeremur, multo minus a vero, quod idem semper et unum est, aberrare potuimus.

However above every thing we have understood that, subsequently to daily talks, advantages are poured on studies of such kind. In fact thanks to our private discussions it happened that we were immediately becoming aware, if everybody in the same way both spoke and thought some phenomenon, or if errors and their location soon were manifested, or finally if we came upon some new method of observation and learning, and, so to say, with united strengths we were aiming at the truth. Just this, that starting from this point, the one of us investigated in a way, the other one in another way about the same studies, the one the clear and distinct knowledge of the phenomena or rather a model, he was able to reproduce with his professionalism; the other a demonstration or a repetition of some anatomical and physiological notions; a third finally waited with calmness and without any premonitory thirst the result, of whatever kind it was: this same difference, I say, of our intentions has been for us of considerable help. In fact to no one of us it would have been permissible to advance more quickly than it was correct, neither we ever accused the lack of rules to follow in constituting the real method of investigation, so much less we would have been able to grow apart of the truth, which is always only one.

[11] Sic omnia consilia nostra studiorum sobrietate, tranquillitate atque assiduitate temperata quasi sunt et ad fines quosdam perducta.

Thus all of our intentions have been, so to say, harmonized by sobriety, serenity and continuity of the studies and addressed to certain aims.

Neque enim reticendum putamus, ea nos teneri spe, fore, ut multum bonae frugis inesse nostrae commentationi judicetur. Uti enim summa cum alacritate et voluntate optima ad rem agendam accessimus; ita res acta nobis videtur voluntatem nostram et exspectationem paene totam sustinuisse. Verum enim vero omnibus ex partibus assequi, quae vel institueramus, vel optaveramus, nobis non contigit. Cum enim non solum universam, qua pulli oriantur et succrescant, rationem penitus evolvere atque explicare apud animum nostrum constituissemus , sed etiam singulas ovique et pulli ipsius partes perscrutari, earumque deinceps factas mutaciones ad unam omnes recensere essemus et describere conati: ramen brevi jntelleximus, patere tanti ambitus commentationem tam late, ut neque otii nostri esset ea res, neque posset, nisi multorum annorum continuo labore, absolvi. Quibus de causis quaestionem nostram ad hanc legem revocare debebamus, ut in hoc de [12] variis ovi incubati permutationibus libello pulli corpus ipsum tanquam unum quoddam ac simplum considerantes, singulas, quibus constat, particulas minus respiciamus. Item non placuit, omnes partium, quibus ovi natura conflata est, vicissitudines persequi, addita tamen eorum narratione, quae obiter a nobis sunt observata. Etenim licet nihil eorum, quae ad cognoscenda varia avis in ovo evolutionis momenta pertineant, praetermisimus: tamen separatis singulorum organorum disquisitionibus non tantum curae atque industriae tribuere licuit, quantum ad omnes errores declinandos requiri videbatur. Quamobrem cum potius nihil mallemus, quam incerta et obscura tradere, non pauca censuimus apud nos reservanda. Quapropter etiam necesse non fuit, ovi incubati descriptionem ultra quintum diem producere. Hoc enim tempore peracto, cum omnium partium fundamenta jacta sint, nihil magnopere memorabile fieri cognovimus. Sunt igitur ea, quae hoc loco disputata et praecepta sunt, quaeque vera esse observationibus nostris probatum diximus, suis illa quidem finibus ac numeris absoluta, ita tamen comparata, [13] ut facile quis sua hoc in genere inventa adjungere deinceps atque adnectere queat. Quid? quod nostrum fortasse ipsorum unus vel alter, (quandoquidem in praesentia dulcis consuetudo nostra fato quodam tristi dissolvitur,) ea posthac augebit atque amplificabit; nihil etiam impedit, quo minus ne alius quispiam, denuo pertractatis, quae a nobis instituta sunt, utilem aeque hanc ac gravem doctrinam sibi deligat propagandam. Ad quem finem quoniam non parum facit, cum rerum apparatum tum omnes agendi operandique et rationes et subsidia cognita habere; addemus earum rerum descriptionem, quibus ipsi usi sumus, quasque alii nostram viam ingressuri non sine magna utilitate usurpabunt.

Neither in fact we think to have to pass under silence the fact that we are motivated by the hope that it is judged that in our treatment there is a lot of good result. In fact, as we approached to the treatment with the greatest ardor and the best good wish, so it seems us that the treatment has almost totally supported our intention and our expectation. But in truth we have not been blessed with achieving among all aspects those results we had proposed or we had wished. In fact, since we intimately decided not only to examine and to explain in depth the cause for which the chicks hatch and develop, but also to appraise one by one the single components of the egg and of the chick itself, and we had tried time by time to pass in review and to describe the mutations singly occurred in the eggs, however we shortly realized that a treatment of so wide wideness covers such a great extension that neither that task was part of the availability of our leisure, nor it could be executed, only with many years of uninterrupted labour. Because of these reasons we would have submit our search to such condition, that in this little book regarding the various changes of the incubated egg, in examining the organism itself of the chick as unitary and simple at all, we devoted less consideration to the single parts, by which it is composed. Equally we didn't like to appraise all the transformations of the parts, by which the nature of the egg is composed, added however the explanation of those phenomena by us incidentally observed. Really, although we not neglected no one of those observations concerning the various phases of the evolution of the bird in the egg, nevertheless it would not have been possible to devote so much care and task to the isolated treatment of the single organs which seemed required for avoiding all the errors. Therefore, although everything seemed preferable to us rather than to profess uncertain and dark doctrines, we decided to hold back more than a few conclusions near us. For this reason it was also not necessary to prolong the description of the incubated egg after the fifth day. In fact, this period passed, after the foundations of all the parts were laid, we recognized that nothing of remarkable attention was happening. Insofar those reflections, discussed and you anticipated at this point, and that, as we said, have been shown as true by our observations, however have been put together in such way, that someone easily could be able each time to add and to connect his own discoveries in this field. What to say of the fact that perhaps one or another of ourselves (since at the present moment our sweet company is dissolved by a very sad destiny), subsequently will increase and will widen those results? Besides nothing prevents that somebody else, after having re-examined what had been examined by us, chooses the task of divulging these theories so useful as authoritative. Since to such purpose not few is useful to be perfectly known, not only the explanation of the facts but also all the aids and benefits of acting and operating; besides the description of those events, which we ourselves have used, and that others intentioned to walk our way will employ not without great profit.

Ovum incubatum vero omne non aliter, nisi aqua superfusa aperiendum est: fiat hoc sub calida, cum de systemate vasorum ac sanguine agatur. Qui autem non massas in ovo contentas considerare, sed in solam rationem, qua foetus gignatur, animi attentionem convertere et ante quintum incubationis diem ovum inspicere statuerunt, curandum iis inprimis id est, ut blastoderma, quippe in quo et per [14] quod omnes foetus immutationes fiant, nudum et ab omnibus aliis partibus separatum obtineant. Hoc fieri potest, si circa cicatriculam, vel formatis jam vasis sanguiferis, circa sinum terminalem, membranae vitelli segmentum exsecetur; quo facto ab immersa in aquam membrana vitelli blastoderma sponte quasi, quod adhaeserat, solet recedere. Jamque ad hoc ipsum necesse est microscopiorum varia genera, nunc minus nunc magis augentia, nunc simplicia nunc composita admoveas. Quodsi velis vel sola oculorum acie, vel simplici eaque magnae potestatis lente adjutus, ad rem ingredi; id cura, ut blastoderma in aquam, ut ante dictum est, immissum, solo quodam nigro superimpositum sit. Nobis quidem ad hunc finem id genus vasorum vitreorum magno fuit usui, quibus horologia minora obtegere solemus. Haec deinde parvulis quibusdam ollis, ad hunc ipsum usum ab opifice effictis et nigro interiori parte colore obductis, imposuimus. Quando porro, quod tum maxime fiet, ubi embryonem voles artis instrumentis aggredi, margines blastodermatis distendendi tibi veniunt; catilli minuti, cera nigra obducti, vel ad [15] subtilissimas membranas cxplicandas religandasque erunt accommodatissimi. Illa, quae supra diximus, horologiorum vitrea praestant hoc quoque, ut embryonem, iis impositum, cum nigro super solo amplius eum contemplare nolueris, possis microscopiis compositis, quae fere nonnisi ab ima parte lucem admittunt, minimo cum negotio submittere. Horumque ipsorum microscopiorum porro maxima cum utilitate tua eliges, quae quam latissimum visionis campum praebeant. Accidit denique illud quoque, ut sepositis his instrumentis ad unius simplicis lentis usum, eumque in parvis efficacissimum, aciem tuam debeas revocare.

In truth every brooded egg must be opened only by pouring water above: this must be done with warm water, since it deals with the circulatory system and the blood. But who decided not to consider the masses contained in the egg, but to address the attention of his mind only to the cause provoking the birth of the fetus, and to examine the egg before the fifth day of incubation, first of all he must take care of maintaining the blastoderma (<envelop of the embryo?>) bare and separated from all the other parts, since in it and through it all the transformations of the fetus are happening. This is possible, if a portion of the membrane of the yolk is cut near the small cicatrix or, having formed by now the blood vessels, near the terminal ansa; when this is done, the blastoderma, which had stuck to it, almost spontaneously withdraws from the membrane of the yolk soaked in the water. And by now, to observe just this phenomenon, it is necessary to put near it various kinds of microscopes, more or less magnifying, now simple now complex. But if it is wanted to examine the event or only with the sharpness of the sight or with a simple lens and besides of great power, we have to do so that the blastoderma, soaked, as it was said before, in the water, is placed on a plan of black colour. Truly to us to this purpose it was of great utility that kind of glass holders, by which we are usual to protect the smaller clocks. Then we set them on some small saucepans, built by an artisan just in sight of this employment and internally smeared of black colour. When besides, a thing that will happen above all when you will handle the embryo with the professional tools, the borders of the blastoderma have to be stretched, very small dishes will be very suitable, covered of black wax, also to stretch the membranes and to connect them among them. Those containers of glass that, as we previously told, serve to protect the clocks, they also allow this, to be able to set, with the least effort, the embryo placed on them – if it was not wanted to be observed for a longer time on a plan of black colour – under the complex microscopes, receiving only the light from the inferior side. You will choose besides with maximum your utility the greatest of these same microscopes, that can offer you the visual field as wider as possible. It also occurs finally this, that having separated these tools to reduce them to the employment of one only simple lens, and moreover of extreme effectiveness when it is a matter of small objects, our own visual sharpness has to be summoned.

Omnis vero haec solertia, in arte posita, ad ea tantum ova pertinet, quae nondum ad quintum diem incubatui tradita sunt. Quo tcmporis spatio elapso, quia totum fere studium in membranis pcrlustrandis versari debet, eo prosperiore successu gaudebis, quo cautius ab omni, si rarissimum forficis usum excipias, acutorum instrumentorum auxilio abstinueris. Ex aqua vero superfusa ne tum quidem, inter operandum, retrahas pullum. Placet hoc adjicere, e periculis nonnullis, quibus [16] reagentia quaedam remedia in ova adhibuimus, nihil nobis esse magnae allatum utilitatis.

In truth this whole diligence, consisting in the professional practice, concerns only those eggs not yet transferred to the brooding within the fifth day. But after this time period, since almost all the study has to deal to examine the membranes, we will enjoy such a happier success, how much greater will be the prudence by which we will renounce any help of pointed tools, with a very rare exception about the use of the scissors. In truth the chick has not to be excluded from a sprinkle of water poured from above neither then, during the operations. I like to add that any great utility has not been brought by some experiments, by which we applied some therapies reacting in the eggs.

Etsi non omnia, quae de ovo incubato literis tradita sunt, ad manus fuerint, tamen multa a nobis, aut plurima diligenter percognita sunt; fructus tamen inde tenuis, ut verum fateamur, perceptus.

Although not all the written doctrines about the incubated egg have been available, nevertheless a lot of them have been known by us, or many of them carefully; nevertheless, to say the truth a modest fruit has been obtained.

In tanta enim auctorum, qui de ovo incubato egerunt, copia pauci inveniuntur, qui vera et utilia docuerint. Eminet inter hos Marcellus Malpighius qui in sua "de Formatione pulli in ovo {disserrtatione} <dissertatione> epistolica," nec non in "appendice repetitas auctasque de ovo incubato observationes continente" praestantissimas nobis reliquit delineationes, licet nimis brevi explicatione illustratas.

In fact in a so great abundance of writers, who treated about the incubated egg, few are found who gave authentic and useful teachings. Among these Marcello Malpighi* is standing out, who in his epistolary dissertation «De formatione pulli in ovo*» and moreover in «Appendix de ovo incubato*» left us very excellent drawings, although illustrated with a too much short explanation.

Non minoris momenti sunt, quae nos summus Albertus de Haller[2] docuit. "Sur la Formation du coeur dans le poulet. Premier {Memoire} <Mémoire>. Exposé des faits. Second {Memoire} <Mémoire>. Précis des observations suivi de reflexions sur le {developpement} <développement>." et postea "Commentarius de Formatione cordis in ovo incubato." Omnem tamen [17] laudem superant egregiae Wolffii[3] observationes, quae partim in libro "Theoria generationis" partim in suo "de Formatione intestinorum" Tractatu, Commentariorum Academiae Scientiarum Imperialis Petropolitanae Tomo XII et XIII inserto, inveniuntur.

Of not smaller importance they are the teachings given by the excellent Albert de Haller. «Sur la Formation du coeur dans le poulet. Premier Mémoire. Exposé des faits. Second Mémoire. Précis des observations suivi de réflexions sur le développement», and afterwards «Commentarius de Formatione cordis in ovo incubato». Nevertheless superior to every praise are the excellent observations of Kaspar Friedrich Wolff, partly in the book «Theoria generationis», partly in his treatise «De Formatione intestinorum», inserted in the tomes XII and XIII of the Commentaria Academiae Scientiarum of Saint Petersburg.

Quod vero aream vasculosam spectat et memoratu dignissimam in illa circulationem sanguinis, solus Spallanzani[4] eas rite cognovit: "De' Fenomeni della Circolazione." In Modena 1773.

But about the vascular area and the circulation of the blood in it, very deserving to be remembered, only Lazzaro Spallanzani adequately knew them: «De’ Fenomeni della Circolazione». In Modena, 1773.

Nec reticere licet observationes accuratas Viri Clarissimi Comitis de Tredern[5]: "Dissertatio inauguralis medica sistens ovi avium historiae et incubationis prodromum."

And it is not allowed to pass under silence the accurate observations of a very illustrious man as the count Louis Sébastien Marie de Tredern: «Dissertatio inauguralis medica sistens ovi avium historiae et incubationis prodromum».