1) THE "CHEZKAS ISUR" OF AN ANIMAL
OPINIONS: The Gemara quotes the teaching of Rav Huna, who does not require that a properly-slaughtered animal be flayed (Hefshet) and cut (Nitu'ach) in order to be examined for internal blemishes before its meat is eaten. Rav Huna maintains that an animal has a Chazakah that it is permitted as long as the Shechitah was performed properly. However, a live animal (before it is slaughtered) has a Chazakah that it is prohibited ("Chezkas Isur") until proven otherwise. Thus, if a question arises with regard to whether the act of Shechitah was performed properly, the animal is presumed to be forbidden due to its Chezkas Isur.
Why does an animal have a Chezkas Isur until it is known that it was slaughtered properly?
(a) RASHI (DH la'Afukei) maintains that the animal's Chezkas Isur is due to the prohibition of Ever Min ha'Chai, eating part of a live animal. When the animal is alive, it is forbidden to be eaten because of the prohibition of Ever Min ha'Chai.
TOSFOS (DH b'Chezkas) questions Rashi's explanation. The prohibition of Ever Min ha'Chai departs as soon as the animal dies. How, then, can that prohibition be the basis of a Chezkas Isur that forbids the animal when it is dead, after the primary prohibition of Ever Min ha'Chai no longer applies?
The RASHBA in Chulin (9a) comments that this question is not so strong. Perhaps Rashi maintains that the principle of "Machzikin me'Isur l'Isur" applies to prohibit the animal after its death. "Machzikin me'Isur l'Isur" means that when an animal was once definitely prohibited for one reason, and now there is a doubt whether it is still prohibited due to a different reason, the rules of Chazakah still apply. The animal remains prohibited until there is conclusive proof that it is permitted.
(b) TOSFOS maintains that the Chezkas Isur of a live animal is based on the prohibition against eating any animal that was not properly slaughtered. This prohibition is an "Isur Aseh" which stems from the Mitzvas Aseh of "Tizbach v'Achalta" -- "You shall slaughter and eat" (Devarim 12:21), which prohibits one from eating meat that was not slaughtered properly. Obviously, this prohibition does not depart from the animal just because it is now dead. (The RITZBA, quoted by Tosfos in Shevuos 24a, DH ha'Ochel, questions the existence of such an Isur Aseh.) (See also Insights to Chulin 9:3.)
2) AGADAH: THE MOST BRAZEN OF ANIMALS
QUESTION: The Gemara says that the dog is the most brazen of all wild animals. However, the Mishnah in Avos (5:20) says that a person should be as brazen as a leopard to do the will of Hash-m. If the Mishnah's intent is to emphasize how brazen one must be in the service of Hash-m, why does it use the leopard as an example and not the dog? Conversely, if the leopard is the most brazen of animals, why does the Gemara here not mention it? (BEN YEHOYADA)
ANSWER: The BEN YEHOYADA answers, based on the BARTENURA in Avos, that the reason a leopard ("Namer") is so brazen is because it is the product of the union between a lioness and a wild boar. As a Mamzer, a product of inappropriate cross-mating, it is particularly brazen, for brazenness is a common trait of Mamzerim (see Bava Basra 58a, Maseches Kalah ch. 1). Any animal that is a Mamzer has that trait, but all leopards have that trait because they are all Mamzerim, and that is why the Mishnah mentions the leopard as an example of how brazen one should be in serving Hash-m. The Gemara here, however, discusses animals which are naturally endowed with the characteristic of brazenness and not animals which are brazen as a result of their pedigree. (See also following Insight.)
3) AGADAH: THE MOST BRAZEN OF NATIONS
QUESTION: The Gemara states that the Jewish people are the most brazen of the nations. The attribute of brazenness is the opposite of the attribute of Bushah (bashfulness, humility). The Gemara in Yevamos (79a) teaches that David ha'Melech ruled that the Nesinim were not fit to marry into the Jewish people because they did not demonstrate the three signs characteristic of the Jewish people, who are "Rachmanim, Baishanim, v'Gomlei Chasadim" (merciful, bashful, and bestowers of kindness).
The MAHARAL (Nesiv ha'Bushah 1) explains that the Jewish people inherited these three natural characteristics from the Avos (see also Beitzah 32b). The attribute of Gomlei Chasadim comes from Avraham Avinu, who excelled in the Midah of Chesed (Bereishis 18:19). They inherited mercifulness from Yakov Avinu who said to his sons, "May Hash-m give you mercy" (Bereishis 43:14). (Yakov Avinu asked Hash-m to grant his descendants mercy in the eyes of others in return for Yakov's own exemplary Midah of Rachamim. Yakov's mercy is also demonstrated in the description of the way he tended the flocks of Lavan, Bereishis 31:38-40.)
They inherited the trait of Bushah from Yitzchak Avinu, whose unique trait was Yir'ah, fear (Bereishis 31:42), from which Bushah derives (Yevamos 79a; see Insights to Yevamos 79:1).
Why does the Gemara here say that the natural tendency of the Jewish people is the attribute of brazenness, while the Gemara in Yevamos says that the natural tendency of the Jewish people is Bushah? (MAHARAL ibid.)
ANSWER: The MAHARAL explains that there are two types of Bushah. One type comes from a person's lack of motivation and assertiveness. This type of Bushah manifests itself in one who is easily discouraged from taking any initiative because of his shame.
The other type of Bushah is the feeling which one experiences when he realizes that someone else is greater than he, and he thus submits himself to that person.
The Jewish people are brazen with regard to the first type of Bushah, which they entirely lack. The Jewish people have a great degree of initiative and assertiveness. They are always spirited, creative, and innovative.
With regard to the other type of Bushah, however, the Jewish people excel, for they submit themselves to Hash-m and recognize that they are nothing in front of Him. It is in that sense that they are Baishanim (the positive type of Bushah). The Nesinim lacked this positive Bushah and therefore David ha'Melech rejected them. (See, however, the Maharal in NETZACH YISRAEL ch. 14.)
3) HALACHAH: GOING OUTSIDE WITH A WALKING STICK ON YOM TOV
OPINIONS: The Gemara states that a blind man may not carry a walking stick outside on Yom Tov. RASHI explains that "it is the manner of the weekday" to carry a walking stick "and is disrespectful to Yom Tov" (because it gives the appearance that he intends to take a lengthy walking trip).
The Gemara's ruling is recorded as the Halachah (SHULCHAN ARUCH OC 522:1). The MISHNAH BERURAH adds that it applies to any person who walks with a cane.
To what extent does this Halachah apply today? Is a person who needs a cane in order to walk restricted from going outside on Yom Tov?
(a) The ROSH (3:5) writes that the Gemara's prohibition against walking outside on Yom Tov with a walking stick applies only to a stick that helps him walk straight. If he cannot walk at all without the stick, he may carry it out on Yom Tov (as the Gemara teaches in Shabbos 66a).
(b) The YAM SHEL SHLOMO writes that one is permitted to go outside with a walking stick on Yom Tov in Reshus ha'Yachid, or even in a semi-private Karmelis (such as a "Chatzer she'Einah Me'ureves," a communal courtyard which has no Eruv Chatzeros), as long as one does not walk in Reshus ha'Rabim or any public thoroughfare (even though carrying other objects in those places is permitted on Yom Tov).
HALACHAH: RAV MOSHE FEINSTEIN zt'l (Igros Moshe OC 5:19) writes that although many people have the practice to walk in public areas with a walking stick on Yom Tov (even when they can walk without it), there seems to be no clear reason to permit it (regardless of whether or not the area has an Eruv). He writes that the practice has become so commonplace that it will not help to protest, and therefore "it is better to [let them] do something inadvertently than to [protest and thereby cause them to] do it intentionally." He concludes that in practice it is difficult to find grounds to permit it.
With regard to walking outside on Shabbos or Yom Tov with crutches, see Insights to Shabbos 66:2.