The fourth perek (=chapter) of Masechet Hullin begins on today’s daf (=page). Entitled behemah ha-mekashe leiled – “an animal that encounters difficulty while giving birth” – its focus is on the laws relating to an unborn fetus in its mother’s womb at the time that the mother is slaughtered.
When an animal that is in labor encounters difficulty in delivery, and its owner suspects that it may die, one option is to slaughter the animal. Such a situation raises many questions – not about the animal itself, which can certainly be slaughtered and eaten – but with regard to its fetus. Generally speaking, we assume that ritual slaughter will permit the entire animal, together with everything inside it, to be eaten Just as all of the animal’s internal organs will become permitted by means of shehitah, similarly the fetus, which at the moment of slaughter is part of the animal, will become permitted, as well.
What if the fetus is fully developed, and is viable after its mother’s death. Do we still view it as part of its mother, or do we recognize it as an independent entity? If it was part of its mother at the moment of slaughter, will it need its own shehitah? If we do not recognize it as an independent entity at all, how will that affect those parts of an animal that ordinarily cannot be eaten?
These questions do not only relate to situations where the mother is slaughtered while in distress; the Mishnah simply chose a case where such a situation would most likely occur. Although the case in the Mishnah – where the fetus’ front leg came out – is understood by the Tosafot Yom Tov as an indication, or, perhaps, as a cause of the distress, in fact it is normal for kosher animals to be born front legs first.
In any case, it is clear from the Mishnah that in such a case the fetus becomes permitted as a result of its mother’s slaughter; in the event that the fetus’ head came out it is considered to have been born, and as an independent entity would not become permitted by means of its mother’s slaughter.