Thursday, December 8, 2011

A Note On Nits

In light of the discussion on the previous post regarding lice, I thought it would be appropriate to post something that I wrote for Hirhurim a few years ago and subsequently incorporated into Sacred Monsters (of which a new edition came off the press yesterday).

The Gemara says that one is permitted to kill lice on Shabbos because they spontaneously generate:
Rabbi Eliezer said: One who kills a louse on Shabbos is like one who kills a camel on Shabbos (and has violated Shabbos)… Rav Yosef said: The Rabbis disagree with Rabbi Eliezer in the case of lice, which do not reproduce… (Shabbos 107b)

The Rabbis believed that lice “do not reproduce” – that is to say, they do not hatch from eggs laid by other lice. The medieval and later authorities explain that lice are instead generated from sweat.[1] Accordingly, they are not considered to be life-forms like other animals and they may be killed on Shabbos. The Talmud proceeds to question this, based on a statement that seemingly acknowledges the fact that lice hatch from eggs:
Abaye said: And do lice not reproduce? Surely it was said, “God sits and sustains from the eggs of lice to the horns of aurochsen?” (which shows that lice come from eggs)?

The Talmud responds that this statement should be understood differently and does not in fact mean that lice reproduce in the “eggs of lice”:
– That refers to a species which is called “eggs of lice.”

There are many questions and controversies surrounding this passage, which I deal with at great length in my book Sacred Monsters. Here, I want to focus on one question: the strange nature of the last line of the Talmud cited above. As usually understood, it means that the Talmud is responding that the statement about God sustaining the “eggs of lice” does not actually refer to eggs of lice, but rather to a type of insect which is called “eggs of lice.” This seems extremely strange, to say the least! Why would an insect be called “eggs of lice”? Wouldn’t it be much more reasonable to assume that the phrase really does refer to eggs of lice? Furthermore, the beginning of that statement speaks of the God sustaining “the horns of aurochsen,” which are appendages of an animal rather than a type of animal. Accordingly, the last part of the statement would also be describing the appendages of an animal rather than a type of animal. It thus seems very strange for the Talmud to claim that “eggs of lice” are a type of insect!

Another question that people have on this topic is that nits – lice eggs – are not all that tiny. Certainly they can be seen with the naked eye, albeit with some difficulty. Did people really not know about them?

The truth is that if we look at another section of the Talmud, we find an explicit discussion about nits. In a section relating to the law that a nazir may not have a haircut, the Talmud seeks to determine whether hair grows from the tip or from the root. One argument is based on the position of something called “inba” on a hair as it grows:
Does a hair grow from the root or from the tip? …Let us bring a proof from a live inba, which remains at the root of the hair [as it grows]; if you were to say that a hair grows from its root, then the inba should end up at the tip of the hair!
No, one could still say that it grows from the root, and because the inba is alive, it keeps moving down [as the hair grows].
Let us bring a proof from a dead inba, which is at the tip of a hair; if you were to say that a hair grows from its tip, then the inba should be at the root of the hair!
No, one could still say that it grows from the tip, and because the inba has no strength [to grip], it slides along it. (Nazir 39a)

This inba is clearly a nit, and we thus see that Sages of the Talmud had observed nits. So why did they state that lice spontaneously generate? And why did they redefine “eggs of lice” to refer to a species of insect?

In order to answer these questions, let us take a look at what people in the ancient world thought about lice. Aristotle has a fascinating discussion in which he makes it clear that he had seen nits, and he even knew that lice laid them. What he did not know was that lice also hatch from them. Rather, nits were thought to be merely the useless result of two spontaneously-generating lice mating with each other:
But whenever creatures are spontaneously generated, either in other animals, in the soil, or on plants, or in the parts of these, and when such are generated male and female, then from the copulation of such spontaneously generated males and females there is generated a something – a something never identical in shape with the parents, but a something imperfect. For instance, the issue of copulation in lice is nits; in flies, grubs; in fleas, grubs egg-like in shape; and from these issues the parent-species is never reproduced, nor is any animal produced at all, but the like nondescripts only. (Aristotle, History of Animals, Book V, Part 1)

If this is how people thought of lice, then our questions are answered. Rashi states that the “eggs of lice” of tractate Shabbos are the inba of tractate Nazir[2] Accordingly, when the Talmud explains that the statement, “God sits and sustains from the eggs of lice to the horns of aurochsen” refers to a species called “eggs of lice,” it does not mean that there is a species of insect called “eggs of lice.” Rather, it is referring to nits – actual lice eggs. It is stating that they are a distinct entity, that are laid by lice, but not from which lice actually hatch. The Talmud is saying that they are called “eggs of lice” because they are egg-shaped organisms that are laid by lice – but they do not hatch into lice, and thus, according to the Talmud, it is still correct to state that lice spontaneously generate.

Some people have a hard time accepting this, because to their minds, it seems absurd to recognize that lice lay eggs but do not hatch from them; to attribute this belief to Chazal is, in their view, accusing Chazal of being "foolish," heaven forbid. However, they are committing a common error of anachronism. That which seems "obvious" to us today is not at all necessarily "obvious" to people in different eras. Examples of this are legion. But in this case, there's a simple rejoinder to be made: Aristotle was certainly a very, very intelligent and knowledgeable person, and yet he believed that lice lay "eggs" but do not hatch from them.

NOTES

[1] Ba’al Halachos Gedolos; Rambam, Hilchos Shabbos 11:3; Rashba, Commentary to Shabbos 12a; Mishnah Berurah 316:38.

[2] Rashi to Avodah Zarah 3b, s.v. beitzei kinnim, and Rashi to Nazir 39a.

38 comments:

  1. As I pointed out in my comment on the previous post, it seems that unhatched lice eggs are very difficult to see, whereas already-hatched empty lice eggs are much easier to see and are definitely visible. This actually matches with this post nicely:
    The lice are laid from 'invisible' eggs. In that sense, lice "do not come from (visible) eggs". The nits that we see are actually garbage - no lice come of them (since they've already hatched).

    Perhaps this is how Aristotle and the ancient world came up with the notion that lice nits are created by lice but don't produce anything. It is effectively true of the visible nits.

    Or perhaps I'm getting carried away. I'm still not even sure how true it is that unhatched lice eggs very difficult to see. Can anyone confirm?

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  2. I should qualify that I believe that the comment I made about Aristotle is pretty unlikely, however. I am also certainly not suggesting that the Chazal knew the (alleged?) fact that I mentioned when making their decisions.

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  3. R. Slifkin,

    For those of us who read and enjoyed Sacred Monsters, has anything changed in the new printing?

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  4. Very little. A couple of corrections, minor additions, a some reorganization and new material in the last chapter.

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  5. There is something here that bothers me greatly, and I'm not sure how to express it.

    Maybe someone can explain why these huge important shifts in language happen.

    The gemora says that you can kill lice because they do not reproduce.

    R Aurbach says that we can kill lice because their eggs are not halachically relevant.

    But the gemora never says that we can kill lice because they don't hatch from eggs, it says because they don't reproduce.

    Why does the discussion shift so drastically to eggs?

    why isn't the conversation focused on Nolad, or reproduction in general? How did this shift happen and why is everybody ok with it?

    I'm realizing now that most of the time that I disagree with one of these analyses it's because of this drastic shift in language which completely changes the focus of the logic/discussion.

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  6. It's synonymous. Ainan parin v'ravin = do not reproduce = do not lay eggs from which other lice are born => lice instead come from other sources.

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  7. Adam, now that I have a son in gan, I've been able to see lice and lice eggs up close. (I got them too, from him, naturally.)

    Lice eggs are, I think, the same size, whether the lice have hatched or not. But I don't think it's easy to see newly-hatched lice (they may not be visible immediately; I don't know). It's difficult, if not impossible, to tell the difference between a nit that has hatched and a nit that hasn't--both are anchored to the hair.

    So it's possible for someone to look at a nit once an hour, say, and still not be able to tell if (or when) the louse has come out.

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  8. "It's synonymous. Ainan parin v'ravin = do not reproduce = do not lay eggs from which other lice are born => lice instead come from other sources."

    That isn't synonymous.

    laying eggs is not the only way to reproduce. Humans reproduce without laying external eggs. Some worms reproduce without live birth or egg laying.

    Further, how does the microcsopic nature of the egg stop the fact that Lice are not new briot but rather come from their parents?

    It's not synonymous or even analogous to what the Gemora is actually arguing here.

    At this point, the conversation is now about 'evidence for spontaneous generation', and it's halachic meaning and not about 'lice can be killed because they don't reproduce' all because of a semantic shift.

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  9. That isn't synonymous.
    laying eggs is not the only way to reproduce. Humans reproduce without laying external eggs. Some worms reproduce without live birth or egg laying.


    Doesn't matter. Ainan parin v'ravin = spontaneous generation

    Further, how does the microcsopic nature of the egg stop the fact that Lice are not new briot but rather come from their parents?

    Personally, I don't think it does!

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  10. We've had our fair share of kinim in our kids' hair, but I never got around to experimenting with the nits. What would happen if one took a few nits from the hair and placed them in a cup or something. Would they not hatch into lice?
    Such an experiment would have been feasable back in the day.
    Does anyone know?

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  11. It's not a question of "feasible." It was feasible to count people's teeth, but everyone still got it wrong!

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  12. Hi,
    At first glance I very much liked your pshat, but thinking about it more, I have an issue with it.
    If what you are saying is correct, why would Abaye ask from a b'raisah? Why not just ask from what people saw - i.e. he should have asked, "they don't reproduce? what about the eggs that we see?"
    The fact that he only knows about the eggs from other statements seems to support the notion that for some reason they were unaware of lice eggs.
    Or, they knew about the eggs, as that other gemara in nazir shows, yet they never made the connection between lice and the nits. I guess that's also problematic, but maybe it's only problematic in an anachronistic sense.

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  13. Again, you are assuming that everyone else thinks and works the same as you.

    He asked from a baraisa because that was, for him, the most powerful way of asking the question.

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  14. Alternatively - he really didn't know about any lice eggs.

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  15. Adam,

    The unhatched body lice eggs are cca 1 mm long. That is not microscopic or invisible by any reasonable definitions of those words. The fact that hatched eggs are somehow easier to spot doesn't change this.

    Also, if you assume that Chazal permitted killing lice due to the size of their eggs, you have to explain why would they forbid killing any other insects with similarly sized or even much smaller eggs.

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  16. "He asked from a baraisa because that was, for him, the most powerful way of asking the question."

    That's a chiddush, no? "lo tehei sh'miah gedolah me'reiyah"
    Do you have any other examples where they ask from a b'raisah instead of asking from metzius?

    "Alternatively - he really didn't know about any lice eggs."

    That would mean he wasn't familiar with the sugyah in Nazir, which perhaps you can say for abaye, but in the continuation (in Shabbos), it seems the gemara is asking the second time about lice eggs, also from a quote. Certainly the gemara here knows about the gemara in Nazir.

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  17. Unhatched eggs are brown and can been seen reasonably easily on hair which is light brown or lighter. Hatched eggs are now empty and so are white, and can be seen easily on light brown and darker hair. The louse sticks the egg to the hair with something very strong - a hatched egg can stay on a hair for a long time after the louse has left. Baby lice are very small and can been seen once you've combed them out, but not easily on a head, whereas adult lice can be seen on a person's head, sometimes just walking along, or else, if you "rummage around." In answer to Bil's partner, I think that the eggs need the warmth of the head to enable them to hatch so even if you could take them off the hair without squashing them, I don't think they would hatch in a cup.

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  18. Right, I found this on a website:

    "Nits will remain alive off the host for up to 10 days; they will not hatch at or below room temperature (68 degrees F)."

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  19. Thanks for this post. I've been bothered by this for a long time. One point I would add, though, is that there are some Rishonim that hold that kinim are fleas, not lice. Are flea eggs visible?
    We don't pasken like those Rishonim, so the question still obviously remains for the other Rishonim.

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  20. "and new material in the last chapter."

    R' Slifkin- will you post the corrected and new material from the new addition of the book on the site?

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  21. Well, this has been an informative discussion. We now, presumably, know that lice eggs - both of the head and body variety, are visible. That would undermine the 'microscopic egg' thesis. We also know from the Aristotle citation that the ancients were, apparently, unaware that those lice eggs actually resulted in a new generation of lice. The argument about a presumed species beitzei kinim' in the gemara in T.B. Shabbat 107b now becomes more understandable. However, if Aristotle is any indication, the ancients were equally unaware that flies and fleas were generated from eggs. If they, too, were considered 'spontaneously generated' why is it not permissible to kill them on shabbat if they annoy you?

    You are then left with one option, it seems to me. There must be a different reason for Bet Hillel permitting killing lice on shabbat. This is what I maintained in my comment on the associated post. Human lice are parasites that are totally adapted to living in humans and feeding on their blood. They can't live in other environments. That distinguishes them from other pests such as flies and fleas. As such they were considered a lower form of life for which there was no biblical restriction of killing on shabbat. Nor did the sages (Bet Hillel and the majority who followed them) expand the killing prohibition to them since they were so annoying (alleviating tzar is a value).

    Those who, like R' Natan, maintain that we can kill lice because the sages mistaken thought them to be spontaneously generated should address the question of why not also kill flies and fleas on shabbat. Do they really believe that the sages were better observers of nature than the Greeks (Aristotle)?

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  22. Y. Aharon,

    It seems to me that you are projecting our knowledge of lice reproduction into ancient times. It's a nice speculation but it needs to be supported by sources to form a feasible theory.

    It somehow reminds of an explanation in a recent sefer Menuchas Ahavah:

    http://4.bp.blogspot.com/_UDRlVcNdFq0/Rmk79LC0h7I/AAAAAAAAAB0/Fn927lPcbIE/s400/LiceBneiBrak.jpg

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  23. The scan:

    http://4.bp.blogspot.com/_UDRlVcNdFq0/Rmk79LC0h7I/AAAAAAAAAB0/Fn927lPcbIE/s1600/LiceBneiBrak.jpg

    From: http://hirhurim.blogspot.com/2007/06/r-ovadiah-yosef-on-sages-and-science.html

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  24. “God sits and sustains from the eggs of lice to the horns of aurochsen."

    The problem with your explanation is this: How does sustaining egg-shaped organisms that do not hatch demonstrate G-d's compassion? The context of this Talmudic passage shows that sustaining everything "from the eggs of lice to the horns of aurochsen" is an example of the the shift in activity that occurs in the third quarter of the day when, in order not to destroy the world, G-d abandons the Throne of Justice and assumes the Throne of Mercy.

    What mercy is expressed by sustaining sterile eggs?

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  25. It seems likely to me that the ancient knew of "nits" but had good reason to believe that nits did not become lice. From following this discussion (i.e. by rellyong on the research of others rather than my own) it seems that although nits are visable, hatched egg shells persist in hair long after the lice hatched. Not being able to discern the difference between a live egg and a dead egg, but being able to notice increase in lice infestation it seems reasonable, given the technological limitations of the ancient, for them to believe that Lice eggs are unchanged even as lice infestation get worse. Ergo, nits do not hatch lice, rather lice spontaneoulsy emerge.

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  26. "The problem with your explanation is this: How does sustaining egg-shaped organisms that do not hatch demonstrate G-d's compassion?"

    Perhaps, since they serve no purpose, it is a mercy of Hashem that they continue to exist. This bria is there, and does nothing, but Gd does not mind.

    Human beings would get rid of them if they were doing nothing. We would find them pointless and remove them from existence.

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  27. R. Slifkin,

    “Eggs of lice” and “horns of aurochsen" are examples of synecdoche; what is meant are lice and aurochsen.

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  28. Perfect. In other words, the phrase is really saying that God sustains lice and aurochsen. But it is phrased as talking about the horns of aurochsen and the "nondescripts" generated by lice.

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  29. "Perfect. In other words, the phrase is really saying that God sustains lice and aurochsen. But it is phrased as talking about the horns of aurochsen and the "nondescripts" generated by lice."

    Why do you sound like this is such an outlandish idea?

    It would be a good phrase to say from the smallest to the largest creatures, no?

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  30. how do chareidim respond when you tell them, the translation “eggs of lice”: as nits is rashi's . (see gukovitsky) so if you disgree, you are disagreeing with Rashi not slifkin. ?

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  31. Please answer the questionDecember 11, 2011 at 10:45 PM

    Chazal explicitly say that fleas "parushim" do hatch from eggs and may not be killed on Shabbos.
    Did Aristotle similarly distinguish between lice and fleas?

    If not, then this whole approach is fatally flawed.

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  32. Please answer the questionDecember 11, 2011 at 10:57 PM

    I see from your quote of Aristotle in the post that my question is answered:
    For instance, the issue of copulation in lice is nits; in flies, grubs; in fleas, grubs egg-like in shape; and from these issues the parent-species is never reproduced, nor is any animal produced at all, but the like nondescripts only.
    (Aristotle, History of Animals, Book V, Part 1)

    So it would seem that your understanding of Chazal coming from Aristotle is fatally flawed.
    Care to respond?

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  33. How can inba refer to a nit when the Gemara in Nazir (which you quoted) states "and BECAUSE THE INBA IS ALIVE, IT KEEPS MOVING DOWN [as the hair grows]. This would seem to suggest that inba refers to lice (and not their eggs which don't move)?

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  34. So it would seem that your understanding of Chazal coming from Aristotle is fatally flawed.
    Care to respond?


    I don't understand your objection. My claim is not that Chazal actually read Aristotle and faithfully adopted his views. Rather, we see from Aristotle that certain ideas existed in antiquity.

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  35. Please answer the questionDecember 14, 2011 at 12:14 AM

    Rather, we see from Aristotle that certain ideas existed in antiquity.

    But the idea is a single unit! Either you pay attention to insect eggs to see if they hatch baby insects, or you don't and you rely on conventional wisdom.

    It makes no sense that Chazal were very careful observers of fleas' eggs but suddenly became uncritical consumers of Aristotelian ideas when it came to lice eggs.

    Its a classic "just-so story" about what Chazal believed-- with all the lack of intellectual rigor that it implies.

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  36. That's simplistic and anachronistic. People may have paid attention to some eggs and not others. People may have absorbed some ideas and not others. There was no consistency in antiquity.

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  37. A defining characteristic of the Scientific Revolution was its reliance on experimental science (particularly when such experiments utilized some type of machine or technology). Where ancients were content to speculate, modern science insisted on the need to experiment. It seems so obvious and apparent to us today, but it was not so 2,000 years ago. As such, Chazal, like their contemporaries, engaged in a contemplative science and not an experimental one. Such a framework could allow for theories of spontaneous generation and speculation of hair growth. We don't appreciate how sophisticated even grade school science is in comparison.

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