Uktzin, Chapter 2, Mishnah 2. The subject of our masechta is a pair of categories of matter that cling to food: the yad, which is a handle, and the shomer, which is a guard. What separates the two is precisely what this mishnah will be weighing. Where there is a yad, tumah travels in both directions: tumah reaching the handle reaches the food, and tumah reaching the food reaches the handle. What a yad cannot do is enlarge the food. When we check whether there is a kabeitzah present, the quantity a food must have in order to pass tumah onward, the handle is left out of the calculation. A shomer stands differently. Since its role is to shield the food and keep it intact, halachah treats it as part of the food, and it therefore does enter the count toward a kabeitzah.
A fact of nature to hold in mind
Much of what follows depends on something observable in the physical world, so it is worth noting before we open the words of the mishnah. There are fruits in which the pit lodged inside actually slows the fruit's deterioration. The avocado is the familiar example. Take the pit out and the exposed flesh turns brown almost immediately; leave the pit resting in the mashed fruit and the browning is noticeably delayed. Whether a given pit performs that preserving role or not will determine, in each of our cases, whether it ranks as no more than a handle or as a true shomer.
Pits in general: a handle but not a protector
The mishnah opens broadly. "Kol hagal'inim", all pits, that is, the sizeable pits lodged within fruits, "mitam'os u'mitam'os", they take on tumah and they pass it along. Tumah that reaches the surrounding fruit reaches the pit inside, and tumah that reaches the pit reaches the fruit.
The ruling invites an obvious question. The pit is buried within the fruit, never in contact with anyone's fingers. In what sense is a thing no hand ever touches functioning as a handle? The mefarshim answer that the pit contributes to holding the fruit even without being held itself. Strip a fruit of its pit and it becomes limp; lift it and one is likely to squash it. With the pit in place the fruit keeps its shape and can be picked up without damage. It is that structural firmness, supplied from within, that earns the pit the status of a yad.
And there the pit's status stops: "velo mitztarfos". A standard pit inside a standard fruit stays outside the measurement. Since it is nothing beyond a handle, it contributes nothing toward the kabeitzah that would let the fruit be metamei something further.
The pit of a moist date and the pit of a dried date
Dates are treated next, and with them the ruling shifts. "Gal'in shel reisev", the pit inside a soft, ripened date, "af al pi sheyatza", even where the pit has pushed its way partly out, which happens easily when such a yielding fruit is squeezed, "mitztaref", is included in the shiur. The reason lies in what that pit is doing: in a moist date it is not merely lending the fruit firmness, it is keeping the fruit from spoiling, along the lines described above. Preservation is the work of a shomer, and a shomer measures together with the food.
"Shel yeveishah", in a date that has dried, the relationship between the pit and the surrounding fruit has vanished. The pit is simply sitting there, safeguarding nothing. Hence "einan mitztarfos", it stays out of the count, since nothing about it functions as a guard of this fruit.
If the pit is not what shields a dried date, what is? The mishnah supplies the answer: "lefikach chotzel shel yeveishah mitztaref", the thin membrane that had sheathed the pit. What happens physically is that in the course of drying, this membrane detaches from its pouch around the pit and adheres to the flesh, and in that position it becomes the fruit's protective layer. Serving as the guard, it enters the reckoning of a kabeitzah.
"U'veshel retev einan mitztaref", whereas in the moist date the membrane is excluded, because there it is the pit and not the membrane that is doing the guarding. The outcome is a neat inversion: in the moist date we count the pit and ignore the membrane; in the dried date we count the membrane and ignore the pit.
A pit that partly protrudes
"Gal'in shemiktzaso yatza", a pit that has emerged from the fruit in part. The mishnah's ruling is "shekeneged ha'ochel mitztaref": whichever length of the pit lies alongside the food, meaning the section that still has flesh surrounding it, is included, since that is the section performing the protection. The exposed length, projecting outside the fruit, guards nothing and is left out of the kabeitzah.
A bone with meat on it
The identical logic now governs meat. "Etzem sheyeish alav basar", a bone carrying meat upon it. Think of a chicken leg, the meat wrapped all around the bone. People routinely grasp such a bone, taking hold of bone and meat as one, and it is that grip which makes eating convenient. Yet the mishnah's ruling here, "shekeneged ha'ochel mitztaref", rests on more than convenience: the length of bone enclosed within meat is not only something to hold, it also supports the meat and keeps it in position, making it a shomer. On that basis it is added to the shiur of a kabeitzah.
"Haya alav mitzad echad", but suppose the meat does not wrap the bone and instead rests along a single side of it. The Tannaim disagree.
The first view: "Rebbi Yishmael omer, ro'in oso". In his opinion an evaluation is made. We ask whether the quantity of meat heaped on that one side, were it pared down and spread evenly, would be enough to sheathe the bone on every side, "ke'illu hu makifo betabaas", in the manner of a ring encircling it. Should the answer be yes, the bone qualifies as a shomer for that meat, and the two are measured together toward the necessary kabeitzah.
The second view: "Chachomim omrim, shekeneged ha'ochel mitztaref". In the opinion of the Chachomim no such hypothetical redistribution is entertained. Only the stretch of bone that meat actually covers enters the count; the bare side, uncovered by any meat, does not.
Herbs on a stalk
The mishnah finishes by applying the very same rule to certain plants: "hagon hasiah, ve'eizov, vekurnis", savory, hyssop and thyme. These are grassy herbs whose edible portion often grows out along one flank of the stalk while the opposite flank stays bare. The same division applies: the length of stalk facing the edible growth measures together with the food, and the bare length is disregarded.
One question, then, runs from the first line of the mishnah to the last: is this attached part genuinely serving the food, giving it structure and keeping it from spoiling? Wherever the answer is yes, it is a shomer, and it becomes part of the food's own quantity. Wherever it supplies nothing but something to hold, it remains a yad, transmitting tumah in either direction yet never counting toward the kabeitzah.