Albertus, atque ipsemet Aristoteles sane nostram opinionem non parum tueri videntur, cum vitellum ab albumine tunica propria separari tradant, et versus partes naturales pulli situm, et a spiritualibus eius remotum. Spiritualia autem ex maris semine sunt. Si ergo a spiritualibus vitellus separatus est, semine expertem esse necesse est. Sunt autem ovi tunicae tres[1], eisdem authoribus, una vitellum continens, secunda albumen, quae est tanquam pia mater: tertia testae adhaerens, tanquam dura meninx. Prima tunica intra testam ovi substantiam a testa defendit: secunda, quae mollior est, et albumen continet in pulli generatione secundarum loco est, et pullum complectitur: tertia vitellum ambit. Inter primam et secundam humor quidam crudus nascitur, qui excernitur, dum formatur pullus{:}<.> Alibi etiam Albertus apertissimis verbis, seminis situm pertingere scribit, per totum albumen, usque ad vitellum, huicque versus partem acutiorem ovi infigi idque ego in sectione ovi unum diem incubati observavi. Denique ipsemet iterum Aristoteles[2] incoepta ova, si adhuc parvis coitus desierit, non accrescere testatur, sed si continuetur, {caetera}[3] incremento augeri, iustamque magnitudinem implere. Ova autem dum adhuc parva sunt, lutea esse ex eodem diximus, et in sectione etiam videmus.

Truly it seems that Albertus and Aristotle himself are supporting my opinion not a little, since they report that the yolk is separated from the albumen by a proper tunic - vitelline membrane, and it is situated toward the vital parts of the chick and lies faraway from its respiratory parts. On the other hand the respiratory components arise from the semen of the male. Therefore if the yolk is separated from the respiratory parts it must be devoid of semen. According to those same authors, there are further on three tunics of the egg, one containing the yolk, a second one containing the albumen and which is likewise the pia mater: a third one adhering to the shell like the hard meninx - dura mater. The first tunic inside the shell defends the substance of the egg from the shell: the second one, which is softer and holds the albumen, in the generation of the chick plays the role of the placenta, and wraps up the chick: the third one surrounds the yolk. Between the first and second tunic a certain undigested fluid is created, which is secreted while the chick is being formed. Albertus elsewhere also writes in the clearest language that the distribution of the semen extends through the entire albumen up to the yolk and that the semen is fixing itself on the latter toward the more pointed part of the egg, and I observed this fact in the dissection of an egg that had been incubated for one day. And finally still Aristotle himself testifies that the eggs which already begun inception do not grow if coitus ceased while they are still small, but if coitus continues the remaining eggs they grow in volume and attain their proper size. Then, while the eggs are still small, I said according to his statement that they are yellow, and we also see this by the dissection.

Sed quaeret forsan aliquis, quomodo cum caetera animalia per umbilicum cibum capiant, ova nutriantur; non enim vermium modo per se incrementum recipere verisimile est. Id aperte docet Aristoteles[4] fieri per membranam mollem, quae postea testa efficitur; perfecto enim ovo, durum ac rigidum evadit ita modice, ut exeat adhuc molle[5], siquidem dolorem moveret, si ita exiret. Egressum statim refrigeratum duratur, evaporato humore quam primum, qui exiguus est, relictaque portione terrena. Huius itaque membranae particula quadam umbilicaris, parte acuta principium continetur, tenditque parvis adhuc velut fistula: quod in {eiectitiis} <eiecticiis> inchoatis ovis patet. Nam si avis madefacta, aut alia causa inalgescens eiecit, cruentus adhuc cernitur conceptus, habensque sibi annexam appendiculam umbilicarem, quae ovo amplius increscente obtenditur latius, atque minuitur, perfectoque mucro exitum complet; membrana interior sub hoc umbilico est, quae vitellum, albumenque ab eo disterminet. Ubi iam ad consummationem ventum est, ovum absolvitur totum, et umbilicus ratione non insuper apparet: extremum enim ultimum eius est. Partus ovorum contra atque animal evenit. Animal enim versum in caput, suumque principium nascitur: at ovum quasi in pedes conversum exit. Cuius rei causa, ut diximus, est, quod ovum ea parte, qua principium continetur, adhaeret.

But perhaps someone may ask how eggs are nourishing themselves since other animals take their food through the umbilical cord; for it is not likely that they receive their growth by themselves in the manner of worms. Aristotle clearly shows that growth takes place through that soft membrane which later becomes the shell; for when the egg is completed it becomes so moderately hard and rigid that it issues still soft, since it should cause pain if it issues in that way. Cooled immediately upon being laid, it grows hard since the slight moisture in it suddenly evaporates and the earthly portion is left. Thus in the pointed part a certain umbilical particle of this membrane is held as principle, and in still small eggs it stretches like a little tube: and this is evident in sketchy abortive eggs. For if a soaked bird or chilly for another reason ejected it, the fruit of conception is seen to be still bloody and having attached to it a small umbilical appendage - latebra? - which stretches more as the egg grows larger, and which shortens, and when the egg is completed its sharp part ends its purpose; under this umbilical cord is laying the innermost membrane, which separates the yolk and the albumen from it. When by now the process is completed, the egg is entirely delivered and the umbilical cord is no longer visible because of a reason: for its extremity is the last part of it. The parturition of eggs occurs also in a reverse way in comparison with that of an animal. For an animal is born turned toward the head and its beginning: while an egg comes out as if turned toward the feet. As I said, this occurs because an egg adheres to that part into which the principle is contained.

Ex quibus habemus, quomodo ovum incrementum sumit, ac perfectum excluditur: at quot diebus perficiatur, nondum diximus: hoc alibi[6] etiam Philosophus docet, et Plinius confirmat[7], decima nempe a coitu die magna ex parte. Sed quaerendum est quanto tempore subventaneum ovum maturescat. Hoc enim, quod sciam, veterum nemo tradidit. Videtur autem tardius debere perfici propter caloris penuriam, qui in spermate est. Sperma autem perficit ovum usque ad exitum, quod inde patet, si frangatur ovum perfectum: invenitur id triplici differentia distinctum. Colore enim albius est, utpote purioris substantiae, et substantia densius quam reliquum albumen, ut firmius retineat calorem formantem, ne facile exhalet. Caeterum, ut verisimile est ovum subventaneum tardius quam ex coitu factum perfici, ita me nescire fateor temporis quantitatem, ac differentiam, quam alius quispiam observare poterit, mihi id quaesivisse tantum sufficiat.

We deduce from these remarks how the egg receives its growth and is laid when completed: but I have not yet said in how many days it is accomplished: also the Philosopher explains this elsewhere and Pliny confirms this, and precisely mostly at the tenth day after coitus. But we must wonder within how much time a wind-egg comes to maturity. For none of the ancients so far as I know has handed down this information. However, it seems that it is accomplished later on because of shortage of heat, being the latter in the sperm. For the sperm completes the egg until when it is laid, since from that moment, if broken, it appears to be a perfect egg: it is found to be marked with three different characteristics. For it is whiter in color since it is made up by a purer substance, and more dense as substance than the rest of the albumen, so that it may more firmly retain the molding heat in order that this should not easily be lost. On the other hand, as it is likely that a wind-egg is completed later on than one produced by coitus, so I admit that I do not know the amount and the difference of time which some one else will be able to observe, and it is just enough the fact to have asked myself about it.

Iam vero circa pulli generationis principium Aristoteles a priscorum Graecorum opinione prorsus recedit. Existimabant autem illi, ut Al<c>maeonis Crotoniatis, quem citat ipse Aristoteles[8], et Hippocratis medicorum principis exemplo probari potest, pullum ex vitello constare, nutriri vero ex albumine. In ovo, inquit Hippocrates[9], pelliculae ex umbilico tentae sunt, et reliqua, quae de puero dicta sunt, sic se habere in ovo volucris reperies ab initio ad finem. Et rursus: Volucris {in ovis} <ex ovi> luteo nascitur, hoc modo. Incubante matre ovum calescit, et quod in ovo inest, a matre movetur: Calescens autem id quod in ovo est, spiritum habet, et alterum frigidum ab aëre per ovum attrahit. Ovum enim adeo rarum est: ut spiritum, qui attrahitur sufficientem ei quod intus est, transmittat, et augescit volucris in ovo, et coarticulatur modo eodem, ac consimili, velut puer. Nascitur autem ex luteo ovi volucris: alimentum vero et augmentum habet ex albo, quod in ovo est. Ubi autem deficit alimentum pullo ex ovo, non habens id sufficiens unde vivat, fortiter movetur in ovo, uberius alimentum quaerens, et pelliculae circum dirumpuntur, et ubi mater sentit pullum vehementer motum, putamen excalpens ipsum excludit, atque <haec> fieri sole<n>t in viginti diebus <, et manifestum est quod ita se habent>[10]. Ubi enim excussa est volucris, nullus humor in ovi testis inest, qui sane memorabilis existat. {Expressus} <Expensus> est enim in pullum.

But on the other hand Aristotle completely diverges from the point of view of the ancient Greeks in regard to the generation's principle of the chick. On the other hand, as the example of Alcmaeon of Croton quoted by Aristotle himself and of Hippocrates ruler of physicians can demonstrate, they thought that the chick arises from the yolk but that it feeds on the albumen. In the egg, Hippocrates says, little membranes stretch from the umbilical cord, and the rest of what has been said about the child you will exactly find in a bird’s egg from start to finish. And still: A bird is born from the yellow of the egg in this way. When the mother is incubating the egg gets warm, and that which is in the egg is moved by the mother; while the contents of the egg are getting warm, they have a breathing, and through the egg they attract the other cold air from the atmosphere. For the egg is so porous that it can transmit the air which is attracted in sufficient quantity for what is inside, and the bird grows in the egg, and he moves his joints exactly and quite likewise as a child does. Furthermore the bird is born from the yellow of the egg: but he has his nourishment and growth from the white which is inside the egg. But when the chick lacks the nourishment from egg, and he does not have enough to live by it, perhaps he stirs inside the egg as seeking for more abundant food, and the membranes around him are broken, and when the mother notices that the chick is moving violently, she hatches him by pecking at the shell, and usually all this happens within twenty days, and it is well-known that this is the case. For when the bird is hatched, in the eggshells there is no noteworthy liquid. For it has been used for the chick.

Haec omnia Hippocrates, quibus sane generationis modum egregie, ut tantum virum, quem omnes mirantur, decebat, depingit: verum, quod ex albumine nutriri, et ex vitello constare dicat, id {ossitanter} <oscitanter> fortassis fecerit: nam alioqui id contra omnium sententiam, ac quotidianam experientiam scripsit.

All these things were written by Hippocrates, by which he is admirably describing the manner of the generation, as it was appropriate for so great a man whom everyone admires: but when he says that the chick is nourished by the albumen and is formed out of the yolk, perhaps he did this superficially: for otherwise he wrote that in opposition to opinion of everybody and daily experience.