As we learned on yesterday’s daf (=page), according to the Mishnah if one used a kaneh, or reed to perform shehitah – to ritually slaughter – an animal, the slaughter is valid. On today’s daf, Rav Hisda quotes Rabbi Yitzhak as teaching five laws regarding a kromit shel kana – the husk of a reed. They are –
(i) One must not slaughter with it,
(ii) One must not perform circumcision with it,
(iii) One must not cut flesh with it,
(iv) One must not pick the teeth with it.
(v) One must not cleanse oneself with it.
Regarding the teaching that ‘one must not slaughter with it,’ the Gemara quotes a baraita that puts the husk of a reed in the same category as a flint and glass that are acceptable as implements for kosher slaughter. In response Rav Papaexplains that the situation where the reed can be used is in the case of “simuna of the marshes.”
In all of the cases where Rabbi Yitzhak forbade use of a kromit shel kana it is because there is the danger of splinters breaking away from the reed and penetrating into the matter which is being cut, thereby causing damage or hurt. In the case of slaughtering, for example, it is feared that a splinter will perforate the gullet of the animal, thus invalidating theshehitah. This concern apparently does not exist when using a “simuna of the marshes.” The Arukh brings two possible explanations for this. According to the Ge’onim the”simuna of the marshes” is a particular type of reed that is sharp and does not splinter. The second explanation, which also appears in Rashi and in Rabbenu Gershom, suggests that it is a known type of wild grass that can be used for shehitah after it dries out and hardens.
It appears that the plant referred to by Rashi is the Carex, a genus of plants in the family Cyperaceae, commonly known as sedges. These grow wild in marshes and have lengthy leaves whose width is about one and a half centimeters.