Renaissance science – XXXVIII

There is a strong tendency to regard the so-called scientific revolution in the seventeenth century as a revolution of the mathematical science i.e., astronomy and physics, but as I have pointed out over the years many areas of knowledge went through a major development in the period beginning, in my opinion around 1400 and reaching, not a conclusion or a high point, but shall we say a stability by about 1750. During the seventeenth century one area of knowledge that experienced major developments was that of the life sciences, mostly in combination with medicine. One area that had intrigued humanity for millennia, which found an initial resolution during the second half of the seventeenth and first half of the eighteenth centuries was the puzzle of conception and procreation; in simple words, how are babies made? The starting point of this development is usually taken to be the work of the English physician, William Harvey (1578–1657),

William Harvey portrait attributed to Daniël Mijtens, c. 1627 Source: Wikimedia Commons

better known for his discovery of the blood circulation, who wrote a Exercitationes de Generatione Animalium, which was first published 1651, the main message of which was summed up on the frontispiece by the inscription Ex ovo omnia – All things come from an egg.[1]

The frontispiece Exercitationes de Generatione Animalium showing Zeus freeing all creation from an egg with the inscription Ex ovo omnia – All things come from an egg. Source Welcome Collection

It is not a coincidence that Harvey acquired his doctorate in medicine in Padua a Northern Italian, Renaissance Humanist university. Towards the end of the sixteenth century some of the Renaissance Humanist natural historians and physicians had taken up the study of embryology, not as many as had taken to botany or even as many as had taken to zoology, but the most significant work was produced by Hieronymus Fabricius ab Aquapendende (1533-1619), who was Harvey’s teacher.

As we have seen in this series as a whole, and specifically in the episodes on natural history, the Renaissance Humanists, who regarded themselves as the inheritors of classical antiquity, turned to sources from classical antiquity as their inspiration, motivation, and role models, when undertaking scientific endeavours. For the transition from materia medica to botany the major role model was Dioscorides, for zoology Pliny and Aristotle. For embryology, although both the Hippocratic Corpus and the Galenic Corpus both contain writings on the topic, it was principally to Aristotle that the Renaissance humanists turned as role model.

It has become fashionable in recent times to heavily criticise Aristotle both as a scientist and as a philosopher of science, and even to suggest that he hindered the advancement of science through his posthumous dominance. His critics, however, tend to ignore that he was for his time quite a good empirical biologist. Yes, he got things wrong and also made some, by modern standards, ridiculous statements, but a lot of his biological work was based on solid empirical observation, so with his embryology.

In the Early Modern Period, there was a heated debate between the supporters of two different theories of embryology preformation and epigenesis. The theory of preformation claimed that the male sperm contained a complete preformed, miniature infant, or homunculus, that was injected into the female womb where it grew larger over the pregnancy before emerging at birth. 

A tiny person (a homunculus) inside a sperm as drawn by Nicolaas Hartsoeker in 1695 Source: Wikimedia Commons

Opposed to this the theory of epigenesis in which the form of the infant emerges gradually, over time from a relatively formless egg. The theory of epigenesis was first proposed by Aristotle in his De Generatione Animalium (On the Generation of Animals). This work consists of five books of which the first two deal with embryology. I’m not going to give an account of all that Aristotle delivers here but just note two things. For Aristotle human procreation is the male sperm, activating the female menstrual blood. 

A brief overview of the general theory expounded in De Generatione requires an explanation of Aristotle’s philosophy. The Aristotelian approach to philosophy is teleological, and involves analyzing the purpose of things, or the cause for their existence. These causes are split into four different types: final cause, formal cause, material cause, and efficient cause. The final cause is what a thing exists for, or its ultimate purpose. The formal cause is the definition of a thing’s essence or existence, andAristotle states that in generation, the formal cause and the final cause are similar to each other, and can be thought of as the goal of creating a new individual of the species. The material cause is the stuff a thing is made of, which in Aristotle’s theory is the female menstrual blood. The efficient cause is the “mover” or what causes the thing’s existence, and for reproduction Aristotle designates the male semen as the efficient cause. Thus, while the mother’s body contains all the material necessary for creating her offspring, she requires the father’s semen to start and guide the process.

Source: The Embryo Project Encyclpopedia

 Secondly, he developed his theory of epigenesis by the empirical examination of the foetuses in incubating birds’ eggs.

Guillaume Rondelet (1507–1566) in his Libri de piscibus marinis in quibus verae piscium effigies expressae sunt (1554) and Pierre Belon (1517–1564) in his Libri de piscibus marinis in quibus verae piscium effigies expressae sunt and his Libri de piscibus marinis in quibus verae piscium effigies expressae sunt were both heavily influenced by Aristotle, and both included discussion on reproduction in their works. Famously, Leonardo da Vinci (1452–1519) carried out studies of the human embryo and foetus amongst his more general anatomical investigations but these first became known in the nineteenth century so played no role in the historical development of the discipline. 

A page showing Leonardo’s study of a foetus in the womb (c. 1510), Royal Library, Windsor Castle via Wikimedia Commons

The Italian physician Julius Caesar Aranzi (1529–1589),

Portrait of Julius Caesar Arantius (Giulio Cesare Aranzi, 1530–1589). From the Collection Biblioteca Comunale dell’Archiginnasio, Bologna, Italy. Source.

who was lecturer for anatomy and surgery at the University of Bologna, published his De humano foetu opusculum, which contains the first correct account of the anatomical peculiarities of the foetus in Rome in 1564. Further editions appeared in Venice in 1572 and in Basel in 1579. 

As with much else in sixteenth century zoology, a lead was taken by Ulisse Aldrovandi (1522–1605), who followed Aristotle in making daily examinations of fertilised chickens’ eggs, to follow the development of the embryo. He wrote in his Ornithologiae tomus alter de avibus terrestribus, mensae inservientibus et canoris (1600):

Source: Wikimedia Commons

“ex ovis duobus, et vinginti, quae Galina incubabat, quotidie unum cum maxima diligentia, ac curiositate” (each day, with the greatest care and curiosity, I dissected one of twenty-two eggy which a hen was incubating).

Although he describes in detail his embryological observation the lavishly illustrated volume only contains one picture of embryological interest, that of a chick in the act of hatching. 

Volcher Coiter (1534–1576), a Dutch student of Aldrovandi’s, who, before his studies with Aldrovandi, also studied with Gabriele Falloppio (1523–1562) and Bartolomeo Eustachi (c. 1505–1574), and then Guillaume Rondelet(1507–1566) after his time in Bolgna, and who became town physician in Nürnberg in 1569, also took up the systematic study of the development of chicken embryos at Aldrovandi’s urging.

Source: Wikimedia Commons

He published the results of his studies in his Externarum et Internarum Principalium Humani Corporis Partium Tabulae in Nürnberg in 1572, that is twenty-eight years before Aldrovandi published his.

Source: Welcome Library via Wikimedia Commons

Skeleton of a child from Externarum et Internarum Principalium Humani Corporis Partium Tabulae

It has been speculated that Aldrovandi was in fact publishing the results of Coiter’s research without acknowledgement. In 1575, Coiter published his book on ornithology De Avium Sceletis et Praecipius Musculis, which contains detailed anatomical studies of birds. 

As already stated above the major Renaissance work on embryology was by Hieronymus Fabricius ab Aquapendende (1533-1619), or more simply Girolamo Fabrici.

Source: Welcome Library via Wikimedia Commons

Hieronymus Fabricius got his doctorate in medicine under Gabriele Falloppio (1523–1562) in Padua in 1562. He succeeded Falloppio as professor for surgery and anatomy. Fabricius was responsible for the construction of the university’s first permanent anatomical theatre. Here he gave lectures and anatomical demonstrations dissecting the uterus and placenta of pregnant women in 1586. He began lecturing on the foetus in 1589 and embryology in 1592. 

Fabricius’ work displays attempts to balance traditional views and the knowledge he has won from his work. His first book on embryology, De formato foetu was published in about 1600 with many editions appearing between 1600 and 1620. His studies in embryology were much more extensive than any previous researcher and in this, his first publication on the topic, he divides embryology into three areas, firstly semen and the organs that generate it, secondly how semen interacts and generates the foetus, and finally the form of the foetus. His planned book on semen never appeared and is considered lost and his book on the generation of the foetus, De formation ovi et pulli, was published posthumously in 1621.

L0008411 Plate from “De formato foetu…” Fabricius, 1604 Credit: Wellcome Library, London. Wellcome Images Plate from “De formato foetu…” Fabricius, 1604 Engraving 1604 De formato foetu. [De brutorum loquela. De venarum ostiolis. De locutione et eius instrumentis liber / Fabricius Published: 1604] Copyrighted work available under Creative Commons Attribution only licence CC BY 4.0

In part one of De formato foetu, Fabricius discusses the form of the foetus and uterus based on his dissections. He discusses and criticises Aranzi’s De humano foetu opusculu.

L0008414 Plate from “De formato foetu…” Fabricius, 1604 Credit: Wellcome Library, London. Wellcome Images – Engraving De formato foetu. [De brutorum loquela. De venarum ostiolis. De locutione et eius instrumentis liber Fabricus, Hieronymus Published: 1604 Copyrighted work available under Creative Commons Attribution only licence CC BY 4.0

In part two he discusses the umbilical vessels, placenta etc. He follows the views of Galen and Aristotle although he gives some original but mistaken views on the placenta, which he had examined in greater detail than any previous investigators. 

L0008418 Plate from “De formato foetu…” Fabricius, 1604 Credit: Wellcome Library, London. Wellcome Images – Engraving De formato foetu. [De brutorum loquela. De venarum ostiolis. De locutione et eius instrumentis liber Fabricus, Hieronymus Published: 1604 Copyrighted work available under Creative Commons Attribution only licence CC BY 4.0

De formation ovi et pulli (On the Formation of the Egg and of the Chick) was earlier work than De formato foetu but only appeared in print two years after his death.


This book is also in two parts the first of which deals with the formation of the egg, whilst the second covers the generation of the chick within the egg.

L0012570 Plate from “De formatione ovi et pulli”, Fabricius 1621 Credit: Wellcome Library, London. Wellcome Images Chicken and egg. Engraving De formatione ovi et pulli Fabricius, Hieronymous Published: 1621 Copyrighted work available under Creative Commons Attribution only licence CC BY 4.0

As before, the book is a balance act between the traditional views of Galen and Aristotle, and the knowledge that Fabricius had gained through his own research. Once again, he discusses and criticises Anzani’s views.

Both books are richly illustrated with engraved plates. 

Hieronymus Fabricius books represent the high point of Renaissance embryology and whilst far from perfect they laid the foundations for the work of his most famous student William Harvey. 

[1] The information on Harvey and his book is taken from Matthew Cobb’s excellent, The Egg & Sperm RaceThe Seventeenth-Century Scientists Who Unravelled the Secrets of Sex, Life and Growth, The Free Press, 2006, which tells the whole story outlined in it’s almost 19th century title.


Filed under History of medicine, History of Zoology, Renaissance Science

2 responses to “Renaissance science – XXXVIII

  1. Common, though imprecise, observation strongly suggests that children inherit characteristics from *both* parents. (“He has Uncle Charlie’s chin, but Nana’s nose.”) The homunculus theory directly contradicts this. Aristotle’s theory I guess allows for some maternal inheritance through the menstrual blood. Was this discussed at all among the ancient authorities?

    Another issue with the homunculus theory: infinite regress. I read somewhere that the homunculus contained itself a second-order homunculus, since after all the adult born of the homunculus had to contain its own homunculus. And so on.

    I suppose Christian theology provides a way out, since you only need homunculi up till the Last Judgement.

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