Yoma 85a ~ Talmudic Embryology

In a dispute about whether death is a cessation of breathing or a cessation of the heartbeat, the Talmud suggests that a parallel may be drawn to another dispute, this one concerning the growth of a human embryo:

יומא פה, א

נֵימָא הָנֵי תַּנָּאֵי כִּי הָנֵי תַּנָּאֵי. דְּתַנְיָא: מֵהֵיכָן הַוָּלָד נוֹצָר — מֵרֹאשׁוֹ, שֶׁנֶּאֱמַר: ״מִמְּעֵי אִמִּי אַתָּה גוֹזִי״, וְאוֹמֵר: ״גזִּי נִזְרֵךְ וְהַשְׁלִיכִי״. אַבָּא שָׁאוּל אוֹמֵר: מִטִּיבּוּרוֹ, וּמְשַׁלֵּחַ שָׁרָשָׁיו אֵילָךְ וְאֵילָךְ

Let us say that the dispute between these tanna’im who disagree about checking for signs of life is like the dispute between these tanna’im who disagree about the formation of the embryo. As it was taught in a baraita: From what point is the embryo created? It is from its head, as it is stated: “You are He Who took me [gozi] out of my mother’s womb” (Psalms 71:6), and it says: “Cut off [gozi] your hair, and cast it away” (Jeremiah 7:29). [These verses suggest that one is created from the head, the place of the hair.] Abba Shaul says: A person is created from his navel, and he sends his roots in every direction until he attains the image of a person.

So today we will discuss Talmudic embryology, and focus on the question of how, exactly, the growing embryo forms.

Let’s start with a passage found in the tractate Niddah, that beautifully describes the way a growing fetus lays within the womb.

נדה ל, ב

דרש רבי שמלאי למה הולד דומה במעי אמו לפנקס שמקופל ומונח ידיו על שתי צדעיו שתי אציליו על ב' ארכובותיו וב' עקביו על ב' עגבותיו וראשו מונח לו בין ברכיו ופיו סתום וטבורו פתוח ואוכל ממה שאמו אוכלת ושותה ממה שאמו שותה

Leonardo Da Vinci. Studies of the Fetus in the Womb. Drawn between 1510-1513.

R. Simlai delivered the following discourse: What does an embryo resemble when it is in the bowels of its mother? Folded writing tablets. Its hands rest on its two temples, its two elbows on its two legs and its two heels against its buttocks. Its head lies between its knees, its mouth is closed and its navel is open, and it eats what its mother eats and drinks what its mother drinks...

Talmudic embryology reflected the prevailing Greek theories of the times. But those theories developed without the benefit of microscopes and the other tools later available to scientists. Despite this, sometimes the rabbis of the Talmud were spot on with their embryology. The statement of Rav Simlai is a good example. (He lived in 3rd century CE, and is the rabbi who brought you the famous count of 613 commandments.) It is a perfect description of a growing fetus, written as if Rav Simlai was looking at Leonardo Da Vinci’s famous sketch. But his was not the only talmudic description of a how a fetus grows, so let’s look at some others.

Will the real Abba Shaul please stand up?

As we read on this page of Talmud, Abba Shaul declared that the fetus grows from its navel:

יומא פה,א

מהיכן הולד נוצר מראשו וכן הוא אומר ממעי אמי אתה גוזי ואומר גזי נזרך והשליכי וגו' אבא שאול אומר מטיבורו ומשלח שרשו אילך ואילך

From where is the embryo formed? From its head, as the verse says (Ps.71:6): "From my mother's womb you pulled me out (gozi)". And it says later (Jeremiah 7:29) "Pull out (gozi) your hair and throw it away.." Abba Shaul says that the fetus is created from its navel, and from there it sends out roots in all directions.

But elsewhere Abba Shaul has a different theory:

נדה כה, א

אבא שאול אומר תחלת ברייתו מראשו

Abba Shaul says: The beginning of the formation of the embryo is from its head

The contradiction between these two statements was noted by the great French medieval commentator Yakov ben Meir, known as Rabbenu Tam (d. 1174). He suggested that there is an error in the text before us: In Niddah, it should not read “from its head (מראשו), but “like a locust” (כרשון). Indeed this is the reading found in the important medieval dictionary Sefer HaAruch and echoed centuries later in Marcus Jastrow’s dictionary.

תוספות נדה כה,א, ד’ה תחלת ברייתו מראשו

תימה דבפ' בתרא דסוטה (דף מה:) קסבר אבא שאול תחלת ברייתו מטיבורו ומשלח שרשיו אילך ואילך ונראה לר"ת דגרס כרשון וכן פר"ח ובתוספתא פירש כעין חגב דסלעם מתרגמינן רשון וכן משמע דמיירי בשיעור האברים

Rabbenu Tam’s explanation makes a great deal of sense and leaves Abba Shaul with only one opinion: the fetus develops from the navel. This is not exactly what actually occurs, but to the naked eye it is not too far from it. Interestingly, Maimonides declined to take a position on the matter, and wrote simply that “at the beginning, the body of a person is the size of a lentil…”(תְּחִלַּת בְּרִיָּתוֹ שֶׁל אָדָם גּוּפוֹ כַּעֲדָשָׁה).

“The Talmudic Sages,being true polyhistors, took into account experimental biology as well as popular beliefs.”

— Kottek S. Embryology in talmudic and Midrashic Literature. Journal of the History of Biology 1981. 14 (2): 299-315.

Embryonic Development in Antiquity

In 1934 the British historian and embryologist Joseph Needham published A History of Embryology, in which he traced theories of embryonic development from from antiquity to modern times. In this fascinating book we learn that Hippocrates (c. 460-370 BCE) believed the fetus was formed by extracting breath from its mother, and that a series of small fires within the uterus gave rise to the bones and other organs of the embryo. According to Needham, Aristotle (384-322 BCE) understood that the role of the umbilicus was to nourish the fetus. The vessels of the umbilicus join onto the uterus like the root of a plant and through the cord the fetus receives its nourishment. Elsewhere, Aristotle claimed (contra Abba Shaul) that head of the fetus forms first. Galen (c. 129-216 CE) also used the analogy of the umbilicus serving like the root of a plant. According to him the embryo grew from menstrual blood, and then from the blood that nourished it through the umbilical cord.

What Actually Happens -not from THE head or from the navel

Development of the Umbilical cord. A: The posterior body wall is established. B: the vitelline duct form as the cells form a head and tail end, fold inwards on their lateral sides. C: The umbilical cord forms as the yolk sac and vitelline duct fuse. From O'Donnell K. Glick P, Caty M. Pediatric Umbilical Problems. Pediatric Clinics of North America. 1988 24 (1) 792.

At its earliest stage the embryo consists of a sheet of cells, an amniotic cavity and a yolk sac. The sheet of cells develops a head (cranial) and bottom (caudal) end, and grows around most of the yolk sac. This enclosed yolk sac then grows into the gut of the embryo.  The part of the yolk sac that is not surrounded by the embryo is still connected to it by a thin tube called the vitelline duct.  This duct then fuses with the contained yolk sac, and forms a larger bundle of vessels we call the umbilical cord. This occurs between the 4th-8th week of gestation (calculated from the first day of the last menstrual cycle).  

It is clear then, that the embryo does not grow from the head or from umbilical cord.  As you can see from the diagram, the head develops from the early cells of the embryo as it takes on a cranial-caudal polarity, sometime around 3-4 weeks gestation, when the embryo is about 3mm in length. Neither does the embryo grow from the umbilical cord, as Abba Shaul claimed. In fact it is the umbilical cord that grows out from the early embryo, and not the other way around.

However well understood the process of fetal development may now be, pregnancy remains a time that is often fraught with uncertainty and insecurity. The rabbis of the Talmud articulated these fears with a prayer, that reminds us of the fragility of human development and the relief when it all goes well.

ברכות ס,א

שלשה ימים הראשונים יבקש אדם רחמים שלא יסריח משלשה ועד ארבעים יבקש רחמים שיהא זכר מארבעים יום ועד שלשה חדשים יבקש רחמים שלא יהא סנדל משלשה חדשים ועד ששה יבקש רחמים שלא יהא נפל מששה ועד תשעה יבקש רחמים שיצא בשלום

During the first three days after intercourse, one should pray that the seed not putrefy, [that it will fertilize the egg and develop into a fetus].

From the third day until the fortieth, one should pray that it will be male.

From the fortieth day until three months, one should pray that it will not be deformed, in the shape of a flat fish,

From the third month until the sixth, one should pray that it will not be stillborn.

And from the sixth month until the ninth, one should pray that it will be emerge safely.

Berachot 60a ~ Gender Determination

In the time of the Talmud and for centuries beyond, it was very important for a couple to produce male children. To this end, some rabbis suggested a technique to ensure that a boy was produced. Here it is described in today’s page of Talmud:

ברכות ס, א

וא"ר יצחק אשה מזרעת תחלה יולדת זכר איש מזריע תחלה יולדת נקבה

Rabbi Yitzchak said that if the woman emits seed first she gives birth to a male, and if the man emits seed first she gives birth to a female.

Today we will explore the topic of gender determination in the Talmud.

How to conceive a boy or a girl

In the tractate Niddah the statement about “emitting seed first” comes up several times, and in the name of a few different rabbis. And, as if emphasize its importance, the Talmud offers no fewer than four different supporting proofs for the principal. The first is the one that we just read in the name of Rav Ami:

נדה לא, א

אמר רבי יצחק אמר רבי אמי אשה מזרעת תחילה יולדת זכר איש מזריע תחילה יולדת נקבה שנאמר (ויקרא יג, כט) אשה כי תזריע וילדה זכר 

Rabbi Yitzchak says that Rabbi Ami says:The sex of a fetus is determined at the moment of conception. If the woman emits seed first, she gives birth to a male, and if the man emits seed first, she gives birth to a female, as it is stated: “If a woman bears seed and gives birth to a male”(Leviticus 12:2). 

The suggestion from the verse is that “if a woman bears seed” first, then she will “give birth to a male.” A second proof text from the Torah is provided by Rabbi Tzadok, this time from the story of our matriarch Leah.

תנו רבנן בראשונה היו אומרים אשה מזרעת תחילה יולדת זכר איש מזריע תחלה יולדת נקבה ולא פירשו חכמים את הדבר עד שבא רבי צדוק ופירשו (בראשית מו, טו) אלה בני לאה אשר ילדה ליעקב בפדן ארם ואת דינה בתו תלה הזכרים בנקבות ונקבות בזכרים 

The Sages taught: At first, people would say that if the woman emits seed first she gives birth to a male, and if the man emits seed first, she gives birth to a female. But the Sages did not explain from which verse this matter is derived, until Rabbi Tzadok came and explained that it is derived from the following verse: “These are the sons of Leah, whom she bore to Jacob in Paddan Aram, with his daughter Dinah”(Genesis 46:15). From the fact that the verse attributes the males to the females, as the males are called: “The sons of Leah,” and it attributes the females to the males, in that Dinah is called: “His daughter,” it is derived that if the woman emits seed first she gives birth to a male, whereas if the man emits seed first, she bears a female.

בנדה לא ,א–ב

The Talmud brings a third proof text, this one from the Book of Chronicles:

ויהיו בני אולם אנשים גבורי חיל דורכי קשת ומרבים בנים ובני בנים וכי בידו של אדם להרבות בנים ובני בנים אלא מתוך שמשהין עצמן בבטן כדי שיזריעו נשותיהן תחלה שיהו בניהם זכרים מעלה עליהן הכתוב כאילו הם מרבים בנים ובני בנים והיינו דאמר רב קטינא יכולני לעשות כל בני זכרים 

“And the sons of Ulam were mighty men of valor, archers, and had many sons and sons’ sons”(I Chronicles 8:40). Is it in a person’s power to have many sons and sons’ sons? Rather, because they delay while lying on wives’ abdomen, initially refraining from emitting semen so that their wives will emit seed first, in order that their children will be male, the verse ascribes them credit as though they have many sons and sons’ sons. And this statement is the same as that which Rav Ketina said: I could have made all of my children males,by refraining from emitting seed until my wife emitted seed first. 

And finally, the fourth proof text. A later passage in Niddah (Niddah 70b-71a) cites a number of questions that the sages of Alexandria asked of Rabbi Yehoshua. One of them was how can a man ensure he has male children? Rabbi Yehoshua told them the man should do two things: marry a woman who is fit for him, and act modestly during sexual intercourse. Hold on, the sages of Alexandria replied. Many men have done that, and it didn’t help! Rabbi Yehoshua then qualified his answer, and explained that in addition to marrying an appropriate woman and being modest, a man needs to pray for a son. Rabbi Yehoshua then cited a proof text from Psalms (127:3):

הנה נחלת ה' בנים שכר פרי הבטן

Behold, children are a heritage of the Lord; the fruit of the womb is a reward

So far so good. To have male children a man needs to marry an appropriate wife, act modestly when he is intimate with her, and pray. But now the Talmud asks a question based on the proof text. What is the act for which the reward are children?

א"ר חמא ברבי חנינא בשכר שמשהין עצמן בבטן כדי שתזריע אשתו תחילה נותן לו הקב"ה שכר פרי הבטן

Rabbi Chama, son of Rabbi Chanina, says: In reward for men withholding their semen in their belly in order to allow their wives to emit seed first, the Holy One, Blessed be He, gives him the reward of the fruit of the womb, [that is, sons].

These are the four different proof texts from the Bible to support the claim that if a woman emits her seed first, she will give birth to a boy. Of course now we need to determine what, precisely, is meant by the phrase “if the woman emits seed first” (מזרעת תחילה).

Understanding THE PHRASE

(i) Ovulation

Perhaps it could refer to ovulation. This makes sense to us since we understand that fertilization requires two “seeds,” the egg, and sperm. But this would not have made sense to the rabbis of the Talmud. They, like everyone else at the time (and indeed until the beginning of the seventeenth century) had no concept of mammalian ovulation. In fact it was the blood that was lost at menstruation that was believed to be the mother’s contribution to her child’s formation, and not any eggs she may produce.

A classic example of this lack of understanding of ovulation is found in the early medieval commentary of Moses ben Nachman, known as Ramban (1194–1270) to Leviticus 12:2. Here is the key bit:

כי האשה אע"פ שיש לה ביצים כביצי זכר או שלא יעשה בהן זרע כלל או שאין הזרע ההוא נקפא ולא עושה דבר בעובר

For even though a woman has ovaries like the testes of a man, either they do not produce eggs at all, or else the egg jells and contributes nothing to the fetus.

(ii) Orgasm

The other possibility is that “emitting seed first” refers to orgasm. If you want to have a boy, the rabbis said, the husband should allow his wife to have an orgasm before himself. This interpretation is favored by the historian of all things medical and talmudic, Fred Rosner. Here is what he wrote in Medicine in the Bible and The Talmud (Ktav Publishing and Yeshiva University Press 1977, p175):

It seems obvious…that the meaning must be orgasm rather than ovulation, for otherwise it would not make sense to speak of the men restraining themselves during intercourse in order to allow their wives to “emit seed” first.

Theories of sex determination in Antiquity

In a fascinating paper in the Journal for the Study of Judaism, the scholar Pieter van Horst wrote “it is certain that ancient Greek concepts of embryogenesis influenced Jewish theories about the coming-into-being of a foetus.” So let’s look at some of those theories.

Aristotle (384–322 BCE) recorded the belief (with which he did not agree) that male offspring come from the right side of the male and females from the left side; an embryo that develops in the “right side” of the uterus (whatever that means) becomes male while that which develops in the left side becomes female. Aristotle himself believed that the mother’s contribution to the fetus was menstrual blood, and it had the same origin as male semen, although it was not as developed.

Another Greek, Empedocles (c. 494-434 BCE) thought that “heat” (whatever that means) gave rise to males and cold to females. But the view in the Talmud about editing seed first can be traced further back to another Greek, Democritus of Abdera (c. 460 - c. 370 BCE). Democritus believed that the gender depended on the parent whose semen predominated, “not the whole of the semen, but that which has come from the part by which male and female differ from one another.”

By the time we get to Galen, the Greek physician of the second century, there was an acknowledgement that the mother contributed her own seed, but, as van Horst notes the thought was that“…female sperm is by far less perfect, thinner, and colder than male sperm; it serves only as food for the male semen in its development into an embryo.

“The material surveyed so far covers the period of roughly 500 B.C.E. to 200 C.E. It has shown us that throughout this period a theory about female semen had its place side by side with a theory that denied females a contribution to embryogenesis. ”

— Pieter W. van Horst. Bitenosh's Orgasm. Journal for the Study of Judaism 2012. 43: 613-628.

A new understanding of a Dead Sea Scroll

It is with this background that van Hort explains an enigmatic passage in one of the Dead Sea Scrolls (1QapGen2:9-15), known as the Genesis Apocryphon. It is one of the original Dead Sea Scrolls discovered by Bedouin shepherds in 1946 and now held at The Shrine of the Book in Jerusalem.The scroll recounts a discussion between Noah and his father Lemech, who was worried that Noah was not really his own progeny. “I thought in my heart” says Lemech, “that the conception was the work of the Watchers, and the pregnancy of the Holy Ones, and it belonged to the Nephilim.” He suspects that his wife Bitenosh has committed adultery.

Then Bitenosh, my wife, spoke to me very harshly... (9) and said: 'Oh my brother and lord, remember my sexual pleasure!... (10) in the heat of intercourse, and the gasping of my breath in my breast.'" …(14) Remember my sexual pleasure!... (15) that this seed comes from you, that this pregnancy comes from you…

How, asks van Horst, could Bitenosh think that a reference to the pleasure she experienced when being intimate with Lamech would allay his suspicion? And here is his fascinating solution:

That could only be a convincing argument if that pleasure entailed the conception of their child at the moment the two of them (and no one else) were together. Since the author implies that Bitenosh's argument did convince Lamech, he must have meant her reference to her pleasure to be a conclusive argument. So "pleasure" must here definitely be something much more specific than just the fact that Bitenosh had a pleasant time with Lamech when they begot Noab. That is to say, most probably Bitenosh here refers to her orgasm on that occasion. The fact that not only Lamech but also Bitenosh had an orgasm at that moment is taken as a proof that it is the two of them, together who begot the child. That can only be the case if the female orgasm is here regarded as the event during which she emitted her own seed into her womb where it mingled with Lamech's seed so as to form the beginning embryo. It is only a double-seed theory that can explain why Bitenosh here takes recourse to an appeal to her moment suprême (to which Lamech was witness!) as a cogent argument…

It is fascinating to see how an originally Greek scientific concept here serves to allay the anxious suspicions of a biblical hero.

Yes. It is.

It wasn’t until the invention of the microscope and the work of Antonie van Leeuwenhoek (1632-1723) and Reinier de Graaf (1641-1673), that we began to understand what was really going on. The former described seeing sperm in semen, and the latter dissected pregnant rabbits and described the development of the egg in the ovary. (Fun fact: in his honor, the structure within which the egg matures is known to this day as a Graafian follicle.)

Other ways to have a baby boy

The scholar Moses Gastner who died in 1939 was a lifelong collector of Hebrew manuscripts. These later became part of the collectionso of both the Rylands Library in Manchester and the British Library in London. Gastner also translated the siddur, wrote a history of the Bible, and led the Spanish and Portuguese Congregation in London. Among his many works was a little-known entry (“Birth, Jewish”) in the two-volume Encyclopædia of Religion and Ethics published in New York in 1908. In the entry Gastner included material from his the vast collection of medical and magical manuscripts. Here is one, which Gastner does not date: 

If a woman is anxious to get sons, she must ask a shepherd to get the after-birth of a cow, dry it, and pound it, and drink the powder in wine.

If dried cow after-birth did not suit your tastes, there was this: 

Make a decoration of bear’s or wolf’s meat as much as a bean. If the animal is male the child will be male, and if it is female, the woman will give birth to a daughter.

The Talmud (Niddah 31b) suggested another, perhaps more palatable method to guarantee a baby boy:

אמר רבא הרוצה לעשות כל בניו זכרים יבעול וישנה 

Rava said: One who wishes to make all of his children males should engage in intercourse with his wife and repeat the act.

It’s not a secret any more

At the conclusion of his article on sex determination in the Talmud, Rosner wrote that the Talmud 

emphatically states that if a woman emits her semen first, she will bear a male, and if the man emits his semen first, she will bear a female. We have yet to understand what the Talmud means. The secret of sex predetermination remains hidden.

But this is not correct. We certainly do understand what the Talmud meant, where that meaning came from and what became of it. What once was certainly a mystery (but not a secret) is now well understood. The gender of offspring is determined by chromosomes, and nothing else. 

What actually determines the gender of a fetus

A human egg or sperm each contain 23 chromosomes. All eggs carry an X chromosome; each sperm carries an X or a Y chromosome. If a sperm with an X chromosome fertilizes the egg, the fetus grows into an XX female. If a sperm with an Y chromosome fertilizes the egg, the fetus grows into an XY male. That’s it. Simple.

[Reprint from Niddah 28a].

Niddah 30b ~ Talmudic Embryology

נדה ל, ב

דרש רבי שמלאי למה הולד דומה במעי אמו לפנקס שמקופל ומונח ידיו על שתי צדעיו שתי אציליו על ב' ארכובותיו וב' עקביו על ב' עגבותיו וראשו מונח לו בין ברכיו ופיו סתום וטבורו פתוח ואוכל ממה שאמו אוכלת ושותה ממה שאמו שותה

Leonardo Da Vinci. Studies of the Fetus in the Womb. Drawn between 1510-1513.

R. Simlai delivered the following discourse: What does an embryo resemble when it is in the bowels of its mother? Folded writing tablets. Its hands rest on its two temples, its two elbows on its two legs and its two heels against its buttocks. Its head lies between its knees, its mouth is closed and its navel is open, and it eats what its mother eats and drinks what its mother drinks...

Talmudic embryology reflected the prevailing Greek theories of the times. But those theories developed without the benefit of microscopes and the other tools later available to scientists. Despite this, sometimes the rabbis of the Talmud were spot on with their embryology. Today’s statement of Rav Simlai is a good example. (He lived in 3rd century CE, and is the rabbi who brought you the famous count of 613 commandments.) It is a perfect description of a growing fetus, written as if Rav Simlai was looking at Leonardo Da Vinci’s famous sketch. But his was not the only talmudic description of a how a fetus grows, so let’s look at some others.

Will the real Abba Shaul please stand up?

On page 25a of Niddah Abba Shaul declared that the fetus grows from its head:

נדה כה, א

אבא שאול אומר תחלת ברייתו מראשו

Abba Shaul says: The beginning of the formation of the embryo is from its head

But elsewhere Abba Shaul has a different theory:

סוטה מה, ב

מהיכן הולד נוצר מראשו וכן הוא אומר ממעי אמי אתה גוזי ואומר גזי נזרך והשליכי וגו' אבא שאול אומר מטיבורו ומשלח שרשו אילך ואילך

From where is the fetus formed? From its head, as the verse says (Ps.71:6): "From my mother's womb you pulled me out (gozi)". And it says later (Jeremiah 7:29) "Pull out (gozi) your hair and throw it away.." Abba Shaul says that the fetus is created from its navel, and from there it sends out roots in all directions.

The contradiction between these two statements was noted by the great French medieval commentator Yakov ben Meir, known as Rabbenu Tam (d. 1174). He suggested that there is an error in the text before us: In Niddah, it should not read “from its head (מראשו), but “like a locust” (כרשון). Indeed this is the reading found in the important medieval dictionary Sefer HaAruch and echoed centuries later in Marcus Jastrow’s dictionary.

תוספות נדה כה,א, ד’ה תחלת ברייתו מראשו

תימה דבפ' בתרא דסוטה (דף מה:) קסבר אבא שאול תחלת ברייתו מטיבורו ומשלח שרשיו אילך ואילך ונראה לר"ת דגרס כרשון וכן פר"ח ובתוספתא פירש כעין חגב דסלעם מתרגמינן רשון וכן משמע דמיירי בשיעור האברים

Rabbenu Tam’s explanation makes a great deal of sense and leaves Abba Shaul with only one opinion: the fetus develops from the navel. This is not exactly what actually occurs, but to the naked eye it is not too far from it. Interestingly, Maimonides declined to take a position on the matter, and wrote simply that “at the beginning, the body of a person is the size of a lentil…”(תְּחִלַּת בְּרִיָּתוֹ שֶׁל אָדָם גּוּפוֹ כַּעֲדָשָׁה).

“The Talmudic Sages,being true polyhistors, took into account experimental biology as well as popular beliefs.”

— Kottek S. Embryology in talmudic and Midrashic Literature. Journal of the History of Biology 1981. 14 (2): 299-315.

Embryonic Development in Antiquity

In 1934 the British historian and embryologist Joseph Needham published A History of Embryology, in which he traced theories of embryonic development from from antiquity to modern times. In this fascinating book we learn that Hippocrates (c. 460-370 BCE) believed the fetus was formed by extracting breath from its mother, and that a series of small fires within the uterus gave rise to the bones and other organs of the embryo. According to Needham, Aristotle (384-322 BCE) understood that the role of the umbilicus was to nourish the fetus. The vessels of the umbilicus join onto the uterus like the root of a plant and through the cord the fetus receives its nourishment. Elsewhere, Aristotle claimed (contra Abba Shaul) that head of the fetus forms first. Galen (c. 129-216 CE) also used the analogy of the umbilicus serving like the root of a plant. According to him the embryo grew from menstrual blood, and then from the blood that nourished it through the umbilical cord.

What Actually Happens -not from THE head or from the navel

Development of the Umbilical cord. A: The posterior body wall is established. B: the vitelline duct form as the cells form a head and tail end, fold inwards on their lateral sides. C: The umbilical cord forms as the yolk sac and vitelline duct fuse. From O'Donnell K. Glick P, Caty M. Pediatric Umbilical Problems. Pediatric Clinics of North America. 1988 24 (1) 792.

At its earliest stage the embryo consists of a sheet of cells, an amniotic cavity and a yolk sac. The sheet of cells develops a head (cranial) and bottom (caudal) end, and grows around most of the yolk sac. This enclosed yolk sac then grows into the gut of the embryo.  The part of the yolk sac that is not surrounded by the embryo is still connected to it by a thin tube called the vitelline duct.  This duct then fuses with the contained yolk sac, and forms a larger bundle of vessels we call the umbilical cord. This occurs between the 4th-8th week of gestation (calculated from the first day of the last menstrual cycle).  

It is clear then, that the embryo does not grow from the head or from umbilical cord.  As you can see from the diagram, the head develops from the early cells of the embryo as it takes on a cranial-caudal polarity, sometime around 3-4 weeks gestation, when the embryo is about 3mm in length. Neither does the embryo grow from the umbilical cord, as Abba Shaul claimed. In fact it is the umbilical cord that grows out from the early embryo, and not the other way around.

However well understood the process of fetal development may now be, pregnancy remains a time that is often fraught with uncertainty and insecurity. The rabbis of the Talmud articulated these fears with a prayer, that reminds us of the fragility of human development and the relief when it all goes well.

ברכות ס,א

שלשה ימים הראשונים יבקש אדם רחמים שלא יסריח משלשה ועד ארבעים יבקש רחמים שיהא זכר מארבעים יום ועד שלשה חדשים יבקש רחמים שלא יהא סנדל משלשה חדשים ועד ששה יבקש רחמים שלא יהא נפל מששה ועד תשעה יבקש רחמים שיצא בשלום

During the first three days after intercourse, one should pray that the seed not putrefy, [that it will fertilize the egg and develop into a fetus].

From the third day until the fortieth, one should pray that it will be male.

From the fortieth day until three months, one should pray that it will not be deformed, in the shape of a flat fish,

From the third month until the sixth, one should pray that it will not be stillborn.

And from the sixth month until the ninth, one should pray that it will be emerge safely.

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Next time on Talmudology: When Is a woman most fertile?