1) THE NUMBER OF RIBS IN AN ANIMAL
OPINIONS: The Mishnah (42a) states that when a majority of the ribs of an animal are broken, the animal is a Tereifah. The Gemara quotes a Beraisa that explains that a "majority" of ribs refers to six ribs on each side, or eleven ribs on one side and one on the other side. This implies that an animal has a total of eleven ribs on each side (because the Beraisa says that a majority of ribs on one side is six). RASHI writes that "an animal has twenty-two large ribs that contain marrow, eleven on each side, and thus a majority of the ribs is twelve."
However, upon closer examination, we find that cows have a total of twenty-six ribs, with thirteen on each side! How is this number to be reconciled with the number that the Gemara gives?
(a) The SHACH (YD 54:1) quotes the RA'AVAN who explains that the two ribs on each side of the animal that are closest to the front of the animal are not included in the count of ribs. Rather, they are considered part of the chest ("Chazeh"; they are included in the Matanah of the Chazeh that is given to the Kohen). These four ribs indeed are smaller and softer than the other ribs, which might be a reason why they are not considered ribs but are considered part of the chest. This opinion is quoted by the DA'AS TORAH, DARCHEI TESHUVAH (YD 54:4), and many other Acharonim.
(b) The KAF HA'CHAYIM (YD 54:2) quotes the ZIVCHEI TZEDEK who explains that the four ribs that are not included are the first and last ribs of the animal on each side. The rib towards the front of the animal is considered part of the chest and not a rib, as explained above. The rib closest to the tail of the animal is soft and does not contain much marrow, and thus it is not included in the count of ribs.
These factors are addressed explicitly by Rebbi Yochanan in the Gemara. Rebbi Yochanan states that there are twenty-two "large" ribs, implying that there are other, small ribs that are not included in the count.
Moreover, Rebbi Yochanan says that those ribs contain marrow. The YAD YEHUDAH (54:1) writes that the last rib, although it has some marrow, generally does not have marrow that hardens. However, the SICHAS CHULIN (3:316) takes issue with the relevancy of this finding. He explains that most animals that are brought to the slaughterhouse are large, fully-grown, adult animals. It is known that as animals get older, their ribs get harder until they become bone-like. However, in their younger years the ribs of these animals are softer. He relates that in his experience, the ribs of deer are generally soft, with the first two ribs and the last rib being exceptionally soft.
(It is interesting to note that the OR ZARU'A (#418) makes a very puzzling statement. He states that there are "twenty-three large ribs containing marrow." A similar number is recorded in the text of RABEINU GERSHOM here (in parentheses). Is the Or Zaru'a suggesting that there is a different number of ribs on each side of the animal? The SEDEI CHEMED (volume 5, Ma'areches ha'Tzadi, Klal 10) explains in the name of the SIFSEI KOHEN (Al ha'Torah) that perhaps the Or Zaru'a counts the number of ribs of an animal as twenty-three in order for people not to think that an animal is more important than a person. Man was created with a certain number of ribs, which was then diminished when woman was created (according to one understanding of the opinion of Rebbi Yehoshua in Bereishis Rabah 18:2). Since the number of ribs in humans was diminished, the number of ribs in an animal was also made incomplete. However, in order to reconcile that number with the known number of ribs of an animal, we still must rely on the above answers.) (See Sichas Chulin 3:317.) (Y. MONTROSE)
2) THE POISON IN THE CLAWS
OPINIONS: The Mishnah (42a) discusses animals that become Tereifos by being attacked and clawed ("Derisah") by various types of wild animals and birds. RASHI earlier (42a, DH Derusas ha'Ze'ev) writes that the reason why "Derisah" renders an animal a Tereifah is that the attacker "hits with its claws, and injects poison [into its victim] and burns it." Similarly, Rashi here(DH Aval b'Makom) states that the attacking animal "gets angry, and it has a strong poison which it injects into it (its victim) when it hits it with its claws."
This explanation is difficult to understand. None of the predatory animals and birds listed in the Mishnah have any poison that they inject through their claws into their prey. What is the meaning of Rashi's explanation? (Of course, there is no practical Halachic relevance to whether or not this reason is congruent with scientific observation. As RAV ARYEH CARMELL says in the name of RAV ELIYAHU DESSLER zt'l, the Chachamim received the Halachos through the Mesorah from Har Sinai, and the Chachamim explained the laws based on scientific knowledge that was prevalent at that time. The reasons that they gave do not discount the possibility of other reasons.)
(a) The SICHAS CHULIN (3:342) quotes the ZIVCHEI KOHEN who asks this question. The Zivchei Kohen writes that he heard from a certain person that there indeed are places in the world where animals inject fatal poison from their claws, while, in other places, the same type of attack has no poisonous element.
The Zivchei Kohen himself writes that he was not convinced by this approach until he read a note on the YAVIN SHEMU'AH of the TASHBATZ, which quotes a responsum of the grandson of the Tashbatz, RAV SHIMON DURAN. In summary, he writes as follows: "A wolf once pounced on and clawed a calf, and I agreed to permit [the calf], as my grandfather stated that the wolf does not cause any Behemah Gasah (large, domesticated animal) to become a Tereifah, whether or not the animal is physically large in size. After we gathered to eat the animal, we saw that the area where the animal had been clawed had been eaten away, and the meat opposite the intestines was much redder than usual. The small intestine and the rumen (Keres) also had reddened, changed shaped, and were foul smelling. We forbade the animal to be eaten, in accordance with the opinion that says that a small Behemah Gasah can become a Tereifah if pounced upon by a wolf."
The RIVASH (#447) also says that just because we do not recognize that this is possible does not mean that it is untrue. A similar idea is expressed by the RAMBAM (in Perush ha'Mishnayos to Nidah 3:2) with regard to the Mishnah that discusses people who give birth to beings that resemble fish, grasshoppers, and other creatures.
(b) RAV ARYEH CARMELL, in a footnote to MICHTAV ME'ELIYAHU (4:31, note 4), suggests that the poison described by Rashi might be what is known as "cat-scratch poison." This is infectious bacteria that reside in the claws of the animal due to the decaying remnants of meat that lodge in its claws from previous attacks. It is this "poison" that enters its prey. It is not an actual poison that the animal's body manufactures (like the venom of a snake). Based on this approach, he explains why the Gemara considers a cat an animal that can cause its prey to become a Tereifah, while a dog -- which is generally much larger and stronger -- does not render its victim a Tereifah. Animals that belong to the cat family generally have nails that extend when they pierce their prey and retract into the foot after the attack. This causes the bacteria which cling to the claw to breed inside the foot of the animal and to act as a poison in the next attack.
The SEFER TEMUNEI CHOL (p. 180) cites support for this explanation from various comments of the Gemara. However, he notes that the fact that cats have claws that retract does not explain the "Derisah" of a wolf, which is a member of the dog family and has claws that do not retract. (It could be that a wolf does not need claws that retract in order for infectious bacteria to grow there. See an additional explanation suggested by the Sichas Chulin, end of note 3:342). (Y. MONTROSE)