In his discussion of the sin of wasting seed, R. Yechiel Michel Epstein writes that scientists using microscopes have found that the drop of semen contains the entire image/form of a person, thus explaining why wasting seed is likened to murder:

Aruch Hashulchan E.H. 23:1

וכבר מצאו חכמי הטבע ע"פ זכוכית מגדלת שבטיפת זרע יש כל תמונת האדם והמוציאה לבטלה כאלו הורג נפש ח"ו

However, when it comes to the discussion of prayers that are in vain, he explains that one can only pray for a specific gender for a baby within the first 40 days of pregnancy, because until that point it is mere fluid but at 40 days it gets the form of a fetus:

Aruch Hashulchan O.C. 230:3

וכן מי שהיתה אשתו מעוברת ורצונו בזכר עד מ' יום יכול להתפלל ולומר יהי רצון שתלד אשתי זכר כי עד מ' יום הוה מיא בעלמא אבל לאחר מ' יום שנתרקם צורת הולד ואם מתפלל אז יהי רצון שתלד אשתי זכר ה"ז תפלת שוא דמה שהיה היה ולא ישתנה עוד

What is the difference between the form of a person that already exists in the drop of semen and the form that only comes into existence 40 days into the pregnancy?

  • 1
    I wonder what he was referring to. This was before the discovery of DNA, and there's nothing I know of visible with 1800s microscopes that I could imagine described as the image of a person. Did he simply mean cells?
    – Obie 2.0
    May 8 '18 at 23:25
  • 4
    This is a cool source to base the general question on: now that we know gender is determined from conception by the chromosome in the sperm cell, does the 40 day rule for gender prayers still apply?
    – Double AA
    May 8 '18 at 23:28
  • 2
    @Obie This was a once popular theory. See en.m.wikipedia.org/wiki/Preformationism
    – Joel K
    May 9 '18 at 4:38
  • @Obie this was after the discovery (1881) of DNA. More importantly, it was also after Mendel's theory that some hereditary, congenital substance in the cell controls traits became fashionable in scientific circles (early 1900s).
    – msh210
    May 9 '18 at 4:46
  • @msh210 - I should have been more precise. This was before the discovery of DNA as a genetic carrier. And it was published in 1893, right? So before even what you say about the popularity. I think he was referring to preformationism, as Joel said.
    – Obie 2.0
    May 9 '18 at 5:06

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