On today’s daf we find Rabbi Yehoshua ben Levi offered a number of legal and ethical recommendations to his son. Among then was the statement “Be careful with the veins, in accordance with Rabbi Yehuda.”
The reference to Rabbi Yehuda refers to a Mishna in Massekhet Hullin (daf 27) that teaches one of the most basic rules of ritual slaughter. When performing shehitah the slaughterer must cut two simanim – the esophagus and trachea – in an animal, and a single siman – either the esophagus or the trachea – in a bird. In both cases, it would be sufficient to cut the majority of the simanim (or one of the simanim in the case of a bird). Rabbi Yehuda requires that the arteries should be cut, as well.
Rav Hisda limits Rabbi Yehuda’s teaching to shehitah performed on a bird, since a bird is often roasted whole. Larger animals, however, that are invariably cut into pieces, do not need to have their arteries severed.
The Gemara concludes from this that Rabbi Yehuda’s ruling is not connected with shehitah per se, so much as it is a response to a potential problem with blood becoming congealed in the body of the animal. Therefore, it is not essential that the veins be cut during the act of ritual slaughter, in fact it is sufficient if the arteries are punctured after slaughter, as well. Furthermore, the rishonim point out that if the arteries were not cut during slaughter or punctured after slaughter, nevertheless the bird would still be kosher; it would just have to be cut up, rather than roasted whole, so that the blood would have an opportunity to drain out of the meat.
The term used by Rabbi Yehuda for arteries is veridim – a word that does not appear in biblical Hebrew at all – that refers to the major blood vessels in the neck. The distinction that is made today between veins – the vessels that carry deoxygenated blood from the rest of the body to the heart – and arteries that carry oxygenated blood from the heart to the rest of the body, is a modern concept that was unknown in the time of the Gemara. The Aruk haShulhan rules that Rabbi Yehuda requires that the large veins in the neck near the skin be cut, but most of the poskim, following the Rambam in his Commentary to the Mishna, argue that the reference is to the two arteries that are deeper in the neck, behind the esophagus and the trachea.