[240] Aristoteles olim, nuperque Hieronymus Fabricius, de generatione et formatione pulli ex ovo, accurate adeo scripserunt, ut pauca admodum desiderari videantur. Ulysses Aldrovandus tamen ovi pullulationem ex suis observationibus descripserit; qua in re, ad Aristotelis auctoritatem potius, quam experientiam ipsam collimasse videtur. Quippe eodem tempore Volcherus Coiter Bononiae degens, eiusdem Ulyssis, praeceptoris sui, ut ait, hortatu, quotidie ova incubata aperuit, plurimaque vere elucidavit, secus quam Aldrovando factum est; quae tamen hunc latere non poterant. Aemilius Parisanus quoque, medicus Venetus, explosis aliorum opinionibus, novam pulli ex ovo procreationem commentus est.

Once Aristotle, and recently Girolamo Fabrizi, wrote in a so accurate manner about the generation and the formation of the chick from the egg, that very few things would be regarded as necessary. Nevertheless Ulisse Aldrovandi would have described the generation of the chick from the egg according to his own observations; it seems that on this point he turned the glance to the authority of Aristotle rather than to a true experience. Really in the same period Volcher Coiter, who was dwelling in Bologna, on incitement of Ulisse himself, his own teacher, as he affirms, opened every day incubated eggs and truly he clarified a lot of things, otherwise Aldrovandi did, all things that to the latter would not be remained unknown. Also Emilio Parisano, physician in Venice, after having disapproved of the ideas of others, invented a new generation of the chick from the egg.

Contra Galenus[1] id quod in ovo primum apparet, caput pulli esse existimat. Si igitur pueri generatio in utero eodem modo sese habeat, ut in ovo, quod doctissimis verbis docere Hippocratem medicorum {coriphaeum} <coryphaeum> supra ostendimus, et ex sanguinea illa gutta cor generetur, quod ex palpitatione, quae solius cordis passio est, Aristoteles, Pliniusque probant, et ego meis oculis vidi, non video, quomodo Galeni doctrina defendi queat, dum iecur primum nasci putat. Quominus enim huius partes agam, mihi obstat propria observatio. Ut enim trivialis huius controversiae inter medicos, ac philosophos veritatem indagarem, ex ovis duobus, et viginti, quae Gallina incubabat[2], quotidie unum cum maxima diligentia, ac curiositate secui, et Aristotelis doctrinam verissimam esse reperi: sed quia istaec observatio, praeterquam quod scitu dignissima est, et ad praeteritorum explicationem apprime idonea, et [217] voluptatem in se non mediocrem habeat, placuit eam hoc loco, quo brevius fieri possit, inserere.

Galen*, on the contrary, thinks that what first appears in the egg is the chick’s head. If then the generation of a child takes place in the uterus in the same way it takes place in an egg, a thing that we have shown to be taught by means of most learned words by Hippocrates* coryphaeus - leader - of physicians, and that the heart is generated from that bloody drop since Aristotle and Pliny demonstrate this from the fact that it palpitates, a thing which is typical of the heart alone and I have seen with my own eyes, I do not see how Galen’s doctrine can be defended, as long as he thinks that the liver is created first. It is my own observation which prevents me from taking sides with him. In order to search out the truth in this cheap controversy between physicians and philosophers, each day, with the greatest care and curiosity, I dissected one of twenty-two eggs which a hen was incubating, and I found that Aristotle’s teaching is the true one: but since my such an observation, in addition to the fact that it is very well worthy to be known and extremely fitting for clarify the observations of the past times, is comprising a good deal of pleasure in itself, I thought that it is right to insert it at this point as briefly as possible.

Secundo itaque ab incubatu die, luteum observavi deferri ad cacumen, aliquo pacto alteratum, et in medio quasi subalbidum: cuius rei in primis Aristoteles non meminit. In aliqua vero parte albuminis, quae pariter erat alterata, semen Galli apparebat, quod tres illas videbatur obtinere qualitates, quales iam ante diximus.

On the second day of incubation I observed that the yolk was moving to the sharper end of the egg, and it was altered in some way and almost whitish in the middle: a thing not mentioned first of all by Aristotle*. In some part of the albumen, which was equally altered, there appeared the rooster’s semen, since it showed to have those three characteristics which I have already described before.

Tertia die ablato putamine in parte ovi obtusa, vidi albumen, et reliquam substantiae ovi partem in superiori putamine separatam. Recesserat autem albumen aliquantulum a putamine, quemadmodum fieri videmus in ovis omnibus, quae minus recentia sunt. Hinc Plinius[3] ova schista appellat tota lutea, quae triduo incubatu tolluntur. Vocat autem schista, teste Hermolao, quia dividantur, et discedat vitellus a candido.

On the third day, after the shell was removed in the blunt part of the egg, I saw the albumen and the remaining part of egg’s substance displaced towards the upper shell. For the albumen had receded a bit from the shell, as we see also to happen in all eggs which are less recent. Hence Pliny* calls schista - split - eggs those which are entirely yellow and are removed at the third day of incubation. According to Hermolaus Barbarus*, he calls them schista  - split - because they split and the yolk separates itself from white.

Videbam item manifeste admodum membranas illas tres, quas ovis inesse ex Alberto dixi, et ex Aristotele etiam colligitur: neque verum est, quod secunda earum sit recenter genita. Si enim illud ita esset, minime in ovis nondum incubatis conspiceretur. Inest autem et his, ut etiam vidi, sed albior in incubatis caloris causa. Eadem die vitellus videbatur versus ovi partem acutam: atque hoc est, quod dicebat Philosophus[4]. Effertur per id tempus luteus humor ad cacumen, ubi est ovi principium, nam ibi est maior calor, et vis spermatis. Apparebat etiam in albumine exiguum velut punctum saliens, estque illud quod Philosophus cor statuit. Ex eo vero evidenter admodum videbam enasci venae trunculum, et ab hoc duos alios ramulos proficisci, qui meatus illi fuerint sanguiferi, quos ad utranque tunicam ambientem vitellum, et albumen protendi ille dixerat. Sum autem omnino eius sententiae, ut eiusmodi vias credam esse venosas, ac pulsatiles, sanguinemque in iis contineri puriorem, principalium membrorum generationi, iecoris nempe, et pulmonis, similiumque idoneum: adeo ut recte dixerit Philosophus[5], tertia die signa apparere, an ova foecunda sint futura: licet eiusmodi observatio in maiorum avium, utpote Cycnorum, Anserum, ac id genus aliarum ovis locum minime habeat. In eiusmodi enim, ut idem Philosophus testis est, paulo tardius ea signa apparent.

And so as well I saw quite clearly those three membranes situated inside the eggs, as I said when quoting Albertus* and as it is possible to catch also from Aristotle: and it is not true that the second membrane is recently generated. For if this were so, it would by no means be visible in eggs not yet incubated. On the other hand it is present in these eggs, as I also saw, but is more white in incubated eggs because of heat. On the same day the yolk was towards the sharper end of the egg: and this is what the Philosopher said. During this time the yellow liquid moves to the pointed part where the principle of the egg is located, for the heat is greater there as well as the force of the sperm. It was also visible in the albumen something like a small jumping speck, and this is what the Philosopher established as the heart. Truly, I saw quite clearly arising from it the little trunk of the vein, and from this two other branches coming forth, which would have been those blood-ducts which he said to go towards the two tunics surrounding the yolk and the albumen. In fact I am entirely of Aristotle’s opinion, since I believe that such ducts are venous, and pulsating, and that the blood they contain is purer, suitable for generation of main organs, particularly of liver and lungs, and similar structures: so much so that the Philosopher rightly said that on the third day there appear the signs whether the eggs will be fertile: although there is very little room for such an observation in eggs of larger birds as swans, geese and other similar fowls. For, as also the Philosopher testifies, these signs appear a little later in such birds.

Quarta die bina videbantur puncta, et quodlibet eorum sese movebat: quae haud dubio cor, et iecur fuerint, quae viscera in ovis triduo incubatis idem dixit. Apparebant item duo alia puncta nigricantia, nempe oculi: et iam luteum manifeste ad acutam ovi partem, ubi maior calor est, et spermatis vis sese receperat. Trahitur autem a spermate illud pro carnis generatione, ut in omnibus animantibus fit, quae sibi simile generant.

On the fourth day two points were visible and each of them moved: without doubt they were the heart and the liver, viscera he said to be present in eggs incubated for three days. There also were visible two other blackish specks, precisely the eyes: and now the yolk clearly withdrew towards the pointed pole where the heat is greater as well as the force of the sperm. For it is attracted by the sperm for the generation of the flesh, as it happens in all living creatures which generate a creature looking like themselves.

Quinta die non amplius punctum illud quod cor esse diximus, extra videbatur moveri, sed obtegi, ac cooperiri, et duo illi meatus venosi evidentiores conspiciebantur, alter vero maior altero: nec verum est, quod Albertus scripsit, apparere in tunica illa, quae albumen includit: nisi forte id de tertia tunica, seu secundina dixerit, cui evidenter venae insunt, nam alioqui in illa nullius venae vestigium inerat. Harum venarum insita vi reliqua albuminis portio quasi in palearem colorem immutatur. Videbantur etiam ramuli ad locum tendere, in quo caput formatur, eo scilicet puriorem materiam, a qua caput, ac in eo cerebrum fiat, una cum virtute formatrice deferentes. Erat autem capitis fabrica valde rudis adhuc ac informis: oculi vero conspectiores, atque ervi quasi magnitudine.

On the fifth day that speck which I said was the heart did not seem to move more, but that it was hidden and covered up, and those two vein-ducts were more evident, one larger than the other: and it is not true what Albertus wrote, that they appear in that tunic which encloses the albumen: unless perhaps he was alluding to the third tunic - allantoid, or afterbirth, in which there are clearly visible veins, for however there was no trace of a vein in that enveloping the albumen. By the inborn force of these veins the remaining portion of the albumen changes to a sort of straw color. Little branches seemed to tend to the place in which the head is formed, carrying to it, along with the molding force, a purer material from which the head is formed and, within it, the brain. The sketch of the head was still quite rough and shapeless: the eyes, to say the truth, were more visible and nearly of the size of a lentil.

Sequenti dein die ablato superiori partis obtusae putamine, eiectisque duabus prioribus tunicis, tertia evidenter cernebatur venulis referta: de hac locutum fuisse Philosophum[6] arbitror cum inquit: Membrana etiam fibris distincta sanguineis: atque haec meo iudicio secundina dici potest. Dein inter hanc, et quartam membranam, quae foetum involvebat, humor erat aquosus: quem autumo serosam albuminis partem esse, quae post natum foetum superest, tanquam ad generationem inepta. Eam vero membranam innuere videtur Aristoteles a meatibus illis venarum ortum ducere, quatenus scilicet vi fibrarum a venoso illo meatu ortarum in palearem, vel sanguineum colorem immutatur. Cernebatur deinde totus foetus moveri, et oculi iam maiores erant, quam in praeterita die: at partes inferiores, thorax nempe, venter, et pedes, erant valde imperfectae, nec discerni adhuc poterant, et rostrum erat muccosum: ut recte dixerit Aristoteles[7]: pars inferior corporis nullo membro, a superiori distingui inter initia cernitur. Caput denique tota inferiori corporis parte maius erat.

Then on the following day - the sixth - when the upper part of the blunt end of the shell was removed, and the two first tunics were taken away, the third tunic covered by little veins was clearly visible: I think the Philosopher spoke of this one when he said: Also a membrane marked with bloody fibers, and this in my opinion can be called afterbirth. Then between this tunic and the fourth, which enveloped the foetus, there was a watery liquid: which I believe is the serous part of the albumen, which is left over after the foetus is born, being unfit for generation. Aristotle seems to hint that this membrane takes its origin from those vein-ducts since by the force of the fibers arising from that vein-duct it is changed to a straw or bloody color. Moreover the entire foetus was seen to move and the eyes were by now larger than on the day before: but the lower parts, and precisely thorax, belly and legs were quite imperfect, neither they could yet be discerned, and the beak was mucous: as Aristotle rightly said: at the beginning the lower part of the body cannot be distinguished from the upper part through any organ. Finally, the head was larger than the entire lower part of the body.

Septima die aperta quarta tunica foetum conspeximus parvum adhuc, ac indistinctum cum oculis tamen magnis, triplicique in illis humore, crystallino nempe, vitreo, et aqueo. Aperto capite iam cerebrum aperte cernebatur, minus vero reliquae partes. Unde dicebat Philosophus[8]. Paulo post (intelligit meo iudicio diem quintam usque ad nonam inclusive) et corpus iam pulli discernitur, exiguum admodum primum, et candidum, conspicuum capite, et maxime oculis inflatis, quibus ita permanet diu, {uti nos conspeximus:} <uti nos conspeximus:> et sero, inquit, [218] decrescunt oculi, et se ad ratam proportionem contrahunt; quod quidem verissimum est: siquidem in quartadecima, aut quintadecima die aliquantum resident diminuti propter caloris digestionem.

On the seventh day, when the fourth tunic - amnios - was opened, I saw the foetus still small and indistinct, with eyes nevertheless large and a triple humor in them, and precisely crystalline, vitreous, and aqueous. After the head was opened the brain was by now clearly visible, but less the remaining parts. Hence the Philosopher was saying: A little later (he means, in my judgment, the fifth to the ninth day inclusive) the body of the chick is now visible, quite small at first and snow-white, conspicuous with its head and great bulging eyes which remain a long time thus, as I saw: later on, he says, the eyes decrease in size and contract to their proper volume; this is quite true: in fact, on the fourteenth or fifteenth day they turn out fairly diminished because of the concoction by the heat.

Octava rursus die oculi maiores adhuc videbantur, utpote ciceris ferme magnitudine. Totum corpus tunc sese velociter movebat, et iam crura, et alae distincte cerni incipiebant. Rostrum tamen interim muccosum adhuc erat. Sed forte quispiam quaerat, cur prius superiores, quam inferiores partes in eiusmodi formatione appareant: cui responsum velim, virtutem, seu facultatem formatricem in superioribus magis quam in inferioribus vigere, quod spiritales sint, et per consequens plus caloris obtineant. Caeterum istaec omnia, quae hac die videbam, sequenti manifestiora apparebant.

Furthermore, on the eighth day the eyes appeared further larger, being that almost had the size of a chickpea. The entire body then moved swiftly and by now legs and wings began to be distinctly visible. Nevertheless the beak was meanwhile still of mucous texture. Perhaps someone might ask why in a formation of this sort the upper parts appear before the lower parts: I would like to reply to him that the formative force or faculty is stronger in the upper parts rather than in the lower ones, since the former are respiratory and consequently have more heat. Furthermore, all the things I saw on this day became clearer on the following day.

Decima die non amplius caput toto corpore maius erat, magnum tamen, ut in infantibus etiam videmus: magnitudinis autem causa est humidissima cerebri constitutio. Quod vero Aristoteles dicit[9] oculos fabis maiores esse, id profecto minime verum est, si de vulgaribus nostris fabis locutus fuerit, cum alioqui ervi, vel ciceris albi magnitudinem non excederent: atque hinc etiam non absurde quispiam colligat fabas antiquorum fuisse rotundas, quales araci sunt, quem ideo fabam veterum quidam existimant. Neque etiam verum est quod tradit[10], {tunc}, <tunc>, scilicet, oculos pupillis adhuc carere. Etenim hae non tantum hac die apparebant, sed duabus etiam praecedentibus, una cum omnibus partibus, ac humoribus. Quod vero ait detracta cute nihil solidi videri, sed humorem tantum candidum, rigidum, et refulgentem ad lucem, nec quicquam aliud, id de crystallino humore mihi dixisse videtur, qui tamen haud solus apparebat, sed vitreus quoque et albugineus, unde non parum hallucinatus videri potest Philosophus, uti etiam Albertus, qui eo tempore nihil duri, et glandulosi in iis reperiri existimat, cum crystallinus humor solidus sit, ac quam maxime conspicuus.

On the tenth day the head was no longer larger than the entire body, but it was large nevertheless, as we also see in newborn children: the reason for its bigness is the very humid constitution of the brain. As to the fact that Aristotle* says the eyes are larger than broad-beans, this is by no means true if he has spoken of our common broad-beans since generally they do not exceed a lentil or a white chickpea in size: and hence someone doesn’t deduce absurdly that broad-beans of the ancients were round like wild peas - Pisum arvense - are, whence some people think they are the broad-bean of the ancients. Nor is it true what he reports, that at that time the eyes still lack pupils. For not only did they appear on this day but also on the two previous days along with all their parts and humors. When he said nothing solid could be seen when the covering is removed but a snow-white humor, stiff and shining in the light, and nothing else, he seems to me to have said this of the crystalline humor, which, however, did not appear alone, but also the vitreous and albugineous - sclera, hence the Philosopher seems to have got the wrong end of the stick, as Albertus* did also, who thinks that at this time there is nothing hard and glandulous, whereas the crystalline humor is solid and very well visible.

Eadem item die vidi omnia viscera, nempe cor, iecur, pulmonem. Cor autem, et iecur erant albicantis coloris: et cordis motus non solum apparebat, antequam foetum aperirem, sed iam secto etiam thorace moveri videbatur. Erat autem pullus involutus quartae illi membranae plurimis venis refertae[11], ne in humore iaceret. Cernebam etiam vasa umbilicalia prope anum ad umbilicum deferri, ibique infer<r>i, ut cibum per illum petat foetus. Vidi denique, quod Aristoteles non advertit, in dorso prope uropygium pennarum principia nigricantia menti humani cuti non absimilia, cui pili abrasi sint.

On the same day I saw all the viscera, that is, heart, liver, lung. The heart and liver were of a whitish color: and the heart’s movement not only was evident before I opened the foetus but it seemed to move even when the thorax had been cut. The chick was wrapped up in that fourth membrane - amnios - filled with many veins so that it would not become immersed in the liquid. I also saw the umbilical vasa near the anus going towards the umbilicus and entering there, so that the foetus might take its food through it. Finally, I saw something Aristotle does not mention: on the back near the uropygial gland* the blackish beginnings of the feathers, very similar to the skin of the human chin when its bristles have been shaved off.

Die subsequenti haec omnia erant manifestiora, et in superioris rostelli extremitate erat quid albidi, cartilagineum, et subduriusculum, quod rursus die decimatertia magis erat conspicuum. Erat autem rotundum milii grano haud absimile. Sagacissima rerum parens natura id ibi fabricasse videtur, ut impediat, ne rostello suo vel venulas, vel membranulas, vel alias quascunque tenerrimas particulas pertundat. Aiunt mulierculae, pullos iam natos cibum capere non posse nisi prius id auferatur.

On the following day all these items were more evident, and on the extremity of the upper beak there was something whitish, cartilaginous and rather hard which afterwards, on the 13^th day, was more apparent - the diamond*. It was round, not dissimilar to a grain of millet. Nature, very shrewd parent of the things, seems to have built this here to prevent that with its little beak he bruises or little veins, or little membranes, or any other quite tender part. Farm women say that new-born chicks cannot take food unless this structure is first removed.

Decimaquarta die pullus iam totus plumescebat. Decimaquinta in digitis ungues albicantes apparebant. Die vero decimasexta ovum aperire placuit in opposita parte, ubi nativa tunica, sed unica tantummodo apparebat, eaque alba. Alteram enim quam in altera parte semper videram, hic observare minime datum est. Itaque dubitabam an ea tantum pro albuminis tutela nata sit, cum scilicet ovum non sit recens, vel ad pulli defensionem in ovo incubato. Nam indies illa magis magisque decidere videtur, et foetum sequi, qui sui gravitate deorsum decidit.

On the fourteenth day the chick was already entirely covered with down. On the fifteenth, whitish nails appeared on its toes. On the sixteenth day I want to open the egg in the opposite part where was visible the tunic belonging to the shell, but only one, and it was white too. For the other one I ever had seen in the opposite side, in this point it is quite impossible to be observed. Thus I was doubtful whether it took birth only for the protection of the albumen when the egg is not recent or for the defense of the chick in the incubated egg. For day by day this tunic seems to fall down more and more and to follow the foetus, which falls downward because of its own weight.

Aristoteles etiam unicam tantum esse eiusmodi tunicam his verbis[12] videtur innuere. Sunt, inquit, quandoque locata ova hoc ordine, prima, postremaque ad testam ovi membrana posita est, non testa ipsius nativa, sed altera illi subiecta: liquor in ea candidus est, quasi diceret, omnes partes in ovo locatae sunt hoc ordine; nempe prima, postremaque ad testam ovi membrana posita est. Intelligit meo iudicio per primam, et postremam membranam, eas membra<na>s recens in incubato ovo genitas, eas videlicet, quas aliquoties appellavi tertiam secundinam, et quartam, quam involventem foetum dixi. Nam cum dicit testae nativam non esse, ostendit nec primam, nec secundam esse, quae ab altera ovi parte reperitur. Videtur igitur excludere hanc nativam sive primam, vel secundam, et intelligere tertiam, quam secundinam saepe vocavi. Cum vero dicit[13], sed altera illi subiecta, intelligit eandem, secundinam nempe testae subiectam, quod vel ex hoc maxime liquet, quod candidum in ea liquorem inesse dicat. Is enim, ut supra ostendi, inter tertiam, et quartam continetur. Hinc manifesto errore Suessanus convincitur, qui ex Ephesio per primam interpretatur eam, quae testae adhaeret, per postremam vero, quae albumini.

Also Aristotle by the following words seems to hint that such a tunic is only one. He says: Since the eggs are set up in this order, set against the eggshell there are a first and a second membrane, the latter not being that belonging to the shell, but being the other lying beneath the first one: there is a snow-white liquid in it, as if he was saying that in egg all parts are arranged in this order; and precisely that the first and the second membrane are set against the eggshell. He means, according to my judgment, by first and last membrane those membranes recently generated in the incubated egg, of course those which I sometimes called the third placental one - allantoid - and the fourth which I said is enveloping the foetus - amnios. For when he says that the membrane is not belonging to the shell he shows that it is neither the first, nor the second which is found in the other side of the egg. He therefore seems to exclude that this one belonging to the shell is the first or the second, and to understand that it is the third, which often I called afterbirth. For when he says, but the other lying beneath it, he means that same membrane, that is the afterbirth one, set against the shell, and this is very clear also from the fact that he says there is a snow-white liquid in it. For this liquid, as I showed above, is contained between the third and fourth ones. Hence the Suessanus - Agostino Nifo* - proves to be in manifest error for he interprets from Michael of Ephesus* as first membrane that which adheres to the shell and as last that which adheres to the albumen.

Quae omnia a nobis observata quotidie in sequentibus diebus evidentiora, utpote in perfectissimo pullo apparebant. Die vero vigesima pullus putamine a parente Gallina ablato hora vigesimasecunda sua sponte exivit. Sequens icon ostendit situm perfecti iam pulli in utero [ovo?[14]].

All these things I daily observed became more evident in the following days, since they were appearing in a quite perfected chick. On the twentieth day, the shell being removed by mother hen, on the twenty-second hour the chick came out by himself. The following picture shows the position of a by now completed chick in the uterus.

[219] Post exclusionem reperi in putamine tunicas duas albas nativas una cum duabus aliis in incubatu genitis, secundina nempe, et quae foetum ipsum involverat, in qua excrementum adhuc inerat subalbidum. Evidenter adhuc apparebant in pullo tria illa vasa umbilicalia, duae scilicet arteriae, et vena una, et orificium umbilici valde erat contractum. Vena vero iecori per alium ramum, qui recta ad illud tendebat, inseri videbatur. Mirum autem erat, quod extra id nihil lutei appareret, cum tamen in cavitate abdominis, ubi intestina sunt, prope anum pullus per umbilicum totum fere id absorbuerat, simul cum quinta tunica, quae id involverat. Tanta autem ibi lutei inerat copia, ut vix duplo plus sit in ovo nondum incubato. Aristoteles etiam scripsit[15], decima ab ortu die si alvus abscindatur aliquid adhuc lutei in ea conspici. Sed consideratione in primis dignum est, quomodo eiusmodi membrana, quam una cum vitello a pullo absumi diximus, post eijciatur. Videtur autem dicendum, quod per eandem viam, {umbilicum} <umbilicum> videlicet, regredi debeat, vel per anum, quod potius credo. Tunicae huic duo vasa implantantur, quorum unum arteriam esse, et a corde proficisci pulsus indicat: alterum vena est, deferturque ad intestina, lutei videlicet vehiculum{:}<.> Hepar erat coloris admodum lutei, forte quod ex luteo per venas attracto nutriatur.

After the chick was hatched I found in the shell its two white tunics together with the two other created during incubation, and precisely the placental one - allantoid - and that which had enveloped the foetus itself - amnios - in which a whitish secretion was still present. In the chick they were still quite clearly visible those three umbilical vessels, that is, two arteries and one vein, and the opening of the umbilicus was greatly shrunk. It was possible to see the vein to plug into the liver by another branch which was straight going towards it. It was remarkable that, besides this, nothing of the yolk was visible, since through the umbilicus the chick had absorbed it almost completely in the abdominal cavity where the intestinal loops are near the anus, along with the fifth tunic which had enveloped the yolk. For there was so great a quantity of yolk that in an egg not yet incubated there is barely more than twice of that amount. Aristotle* also wrote that if on the tenth day from birth the abdomen is cut, one can still see some of the yolk in it. But it is worth noting first of all how a membrane of this sort, which I said is absorbed by the chick together with the yolk, is later thrust out. It seems we should say that it ought to move out through the same passage, that is, the umbilicus, or through the anus, which I should prefer to believe. Two vessels are implanted in this tunic, one of these being an artery, and its pulsation indicates that it proceeds from the heart: the other is a vein and goes to the intestinal loops, evidently the vehicle of the yolk. The liver was of a rather yellow color, perhaps because it was nourished by the yolk attracted through the veins.