Talmudic Science: The Case of Shnei Shvilin - part I

As I have posted a while back, I plan on posting on the subject of scientific statements and facts found in the Babylonian Talmud which are seemingly inaccurate and the approaches offered by traditional Torah scholars to these inaccuracies. This is the first post in the series. In this post and in the next one, I intend to deal with a statement in Talmud that is seemingly based on a mistaken understanding of human anatomy and physiology. My goal is to review and analyze the numerous approaches by traditional Torah scholars. The halakhic ramifications of the differing approaches to the passages discussed below cover vastly different areas in halakha, from the question as of how to circumcise a boy born with hypospadias, to the dilemma of whether it’s permitted to undergo a prostatectomy. My hope is that these question will get cleared up, as we analyze the issue.

In Yevamot (75b-76a) it says:

ההוא עובדא דהוה בפומבדיתא, איסתתים גובתא דשכבת זרע ואפיק במקום קטנים, סבר רב ביבי בר אביי לאכשורי; אמר רב פפי: משום דאתו ממולאי אמריתו מילי מוליתא! במקומה מבשלה, שלא במקומה לא מבשלה.

It once happened at Pumbeditha that a man had his semen duct blocked, and the discharge of the semen made its way through the urinal duct. R. Bibi b. Abaye intended to declare the man fit [for marriage]. R. Papi, however, said to him, 'Because you are yourselves frail beings, you speak frail words; through its proper duct it fertilizes but when not passing through its proper duct it does not fertilize [and therefore the man isn't permitted to marry].'

The implication of this passage is that there are two vessels in the male reproduction organ, one for the passage of urine and one for the passage of semen. This is also how Rashi understood it. To explain the passage he cites the following excerpt from Bekhorot (44b):

ת"ר: שני נקבים יש בו באדם, אחד מוציא שתן ואחד מוציא שכבת זרע, ואין בין זה לזה אלא כקליפת השום, בשעה שאדם נצרך אם נקבו זה לתוך זה נמצא עקר.

Our Rabbis taught: Two channels are in the membrum of a human being, one of which discharges urine and the other semen, and the distance between them is no more than the peel of garlic. If when a person needs to ease himself, and one channel interferes with the other, he is found to be impotent.

Here too, the simple understanding is that there are two vessels (with a divider as thin as a peel of a garlic between them) in the male member, one for urine and the other for semen. However, modern anatomy and physiology show that while the semen and urine originate from different places in the body, the semen coming from the testes and the urine from the urinary bladder, both of them end up exiting the body in the same vessel. This vessel is called the urethra, and comes down from the urinary bladder, passes through a gland called the prostate gland, and from there it continues into the member. In the prostate gland, the urethra has two openings for the two vessels coming up from the testes carrying the sperm. (For an accurate description of the urethra, see Gray's Anatomy 40th edition, ch. 75).

Assuming that I an correct with my understanding of the excerpts I quoted, a very obvious question arises. How could Hazal be mistaken in this issue? This is too obvious! R. Hanokh Dov Padwa (1908-2000) in a responsum on the matter (Heshev Haefod Responsa, II:8) indeed dismisses this understanding due to this question. And R. Padwa bolsters his question with the following Mishna in Mikvaot (8:4):

בעל קרי שטבל ולא הטיל את המים כשיטיל את המים טמא.

A man who had a nocturnal emission and immersed himself [in the mikvah] but did not pass first urine, he again becomes tameh when he passes urine.

This implies that Hazal did know that the urine and semen pass in the same vessel and therefore they said that when urinating after a nocturnal emission it's assumed that some remaining semen have passed and therefore we consider the person to be impure. Actually, this is exactly how Rambam and R. Ovadiah of Bartenura understood the Mishnah. According to their explanation of the Mishna, we have to understand why the Gemara in Yevamot and in Bekhorot do not ask from this Mishnah.

Rashi however, has a different understanding of the Mishna. Rashi in Chulin (24b s.v. Lekesheyatil) explains as follows:

לכשיטיל מים טמא, שמא נשאר בפי האמה צחצוח קרי ויוצא עם מי רגלים.

When he passes urine he become tameh, because it might be that a driblet of the emission has remained on the mouth of the member and it goes out with the urine.

In other words, although there are two vessels, one for urine and one for semen, they unite at the tip of the member. This might also be the explanation how they were able to posit that there are two vessels - or one vessel divided in two - in spite of what can be seen with the naked eye. According to Rashi’s understanding, they thought that the tip -the visible part - is where the vessels are already united.


In Nishmat Avraham, Dr. Avraham Avraham records what R. Shlomo Zalman Auerbach (1910-1995) wrote to him on this matter:

ועל הראיות מהש"ס יתכן שזה בגלל הנקב המשותף שבתוך העטרה, וגם יתכן שעוד לפני העטרה כבר יש רק שביל אחד לשניהם.

And regarding the proof from the Talmud (i.e. the proof R. Padwa brings from the mishna in Mikvaot - Y.), perhaps it is so due to the shared hole within the glans, and it is also possible that even before the glans there is only one vessel for both of them (that is, the two separate vessels unite already within the member.) 

Similarly, R. Auerbach's son-in-law and disciple R. Zalman Nehemiah Goldberg writes (responding to the aforementioned questions posed by R. Padwa) in his booklet “Kuntres Hishtanut Hativa'im” (printed in the back of R. Neriah Gutel’s “Hishtanut Hativa'im B’halacha” Jerusalem 1998, p. 267):

אפשר שבזמן המשנה היו שני שבילין בתוך האמה, אבל לא לכל אורך האמה אלא היה נגמר באמצע האמה, או לכל היותר עד העטרה, ולכן טמא אחר הטלת מי רגלים, שיוצא הש"ז שנשאר שם.

It's possible that in Mishnaic times there were two vessels in the member, but not all along the member, rather, it ended in the middle, or at most up until the glans, and therefore he is tameh after he passes urine, because the remaining semen passes then.

Putting aside the question of what was the actual reality then, and whether nature has changed, we see from R. Auerbach and R. Goldberg's answer that Rashi's explanation in the Mishna answers both of R. Padwa's questions. (It is interesting though, that neither R. Auerbach nor R. Goldberg cite Rashi's explanation to the Mishna in Mikvaot.)


While the above may answer the question of how something so obvious could have escaped  R. Bibi b. Abye and R. Papi,  we still have to understand how such a mistake arose in the first place. As we shall see in the next post in this series, the view that there are two vessels in the member was widespread in the Arab world of the middle ages. Andreas Vesalius (1514-1564), who is credited with rectifying the erroneous Arab beliefs and showing, by anatomical dissection, that there is only one pathway in the male member also proposed an answer to the question how the Arabs came to their errant conclusion. He suggests that since anomalies in the urethra, although quite rare, is a thing that can be seen now and then, it might be that they ended up dissecting such a body and therefore made this mistake. Another possible explanation of this seemingly blatant error is their statement that the divider between the two is as thin as a garlic peel. This could mean to say that it’s is so thin that it can’t be seen with the naked eye. 


Either way, this contradiction was dealt with by many traditional Torah scholars, and in the next post in this series I hope to review their answers and analyze them.