Yoma, Chapter Eight, Mishnah 6. Continuing the discussion of people who are in danger if they do not eat on Yom Kippur, the Mishnah teaches three rulings - two of them in the name of Rabbi Masya ben Charash - dealing with feeding a person who is in danger and with giving medicine to a sick person on Shabbos.
"Mi she'achazo bulmus":
Bulmus is a type of illness that comes from lack of food, and one who is stricken with it is in danger if he does not eat. Therefore the Mishnah rules:
"Ma'achilin oso afilu devarim temei'im" - we feed him even foods that are not kosher.
"Ad she'ya'oru einav" - until his eyesight returns to him. Apparently dimming of vision is one of the symptoms of this illness.
"V'ein mamtinin" - we do not wait until kosher food is found; rather, we give him whatever is available, so that he will eat as quickly as possible.
"Mi shenashacho kelev shoteh":
Here the Mishnah teaches a similar matter, which has no connection to Yom Kippur but rather to the prohibition of forbidden food. A kelev shoteh is a dog stricken with rabies. Regarding this the ruling states: "Ein ma'achilin oso mechatzar kaved shelo" - we do not feed the person who was bitten from the diaphragm of the rabid dog. There were those who held that this had healing properties, and indeed today it is known that rabies comes from the dog, and the material is extracted from it; it is possible, then, that there was something to this from a medical standpoint. Rabbi Masya ben Charash permits it and holds that it is an effective remedy, although according to the Talmud's conclusion we do not follow this, since it is not an effective remedy.
"HaChoshesh bigrono":
Another ruling in the name of Rabbi Masya ben Charash: one who has a certain pain in his throat - "metilin lo sam b'soch piv b'Shabbos", we place medicine in his mouth on Shabbos. And the reason for this: "mipnei shehu sfek nefashos" - this is a situation of doubt, in which there is a possibility of danger to life, "v'chol sfek nefashos docheh es haShabbos" - anything that carries a possibility of danger to life overrides Shabbos.
Although generally we do not give medicine on Shabbos, in such a situation it is certainly permitted. And in practice, actual danger to life is not required in order to give medicine: even if the person is a sick person whose entire body is affected - for example, he needs to lie in bed - that is enough to permit giving him medicine. In the case before us, we are dealing with something that was genuinely dangerous.
In summary: in this Mishnah we learned that one who is seized by bulmus is fed even non-kosher foods until his eyesight returns, and we do not wait for kosher food; that one who was bitten by a rabid dog is not fed from the diaphragm of the dog, and Rabbi Masya ben Charash permits it, although the halachah does not follow him; and that one who suffers from throat pain has medicine placed in his mouth on Shabbos, because a possibility of danger to life overrides Shabbos. From here emerges the broader principle as well: even a sick person whose entire body is affected may be given medicine on Shabbos.