The Sages taught in a baraita: Five signs were said about a mad dog: Its mouth is always open; and its saliva drips; and its ears are floppy and do not stand up; and its tail rests on its legs; and it walks on the edges of roads. And some say it also barks and its voice is not heard.
All of these are symptoms of rabies, a disease that affects the nervous system of an animal, slowly paralyzing it. The Gemara further described the effects of this disease on a person, where without proper treatment (unavailable in the time of the Gemara) it is usually fatal. Among other things, rabies involves a painful contraction of the muscles in the throat which does not allow the victim to swallow. Apparently due to the association with thirst and the inability to drink water, even seeing water was thought to lead to madness, which is why for generations this condition was called “hydrophobia.”
As we learned in the Mishna (83a) Rabbi Matya ben Harash permits the victim of rabies to eat the infected dog’s liver. Although his position is rejected by the poskim, who accept the position of the Tanna Kamma, nevertheless there are those who see in Rabbi Matya’s ruling the foreshadowing of modern methods of medicine where enzymes are taken from the bodies of animals that have been infected and vaccinations are developed using those antibodies.
Another disease discussed by the Gemara is tzefidna, which, from the description in the Gemara, appears to be scurvy, a disease marked by a lack of Vitamin C, which leads to a weakening of teeth and gums, internal bleeding and anemia. The descriptions in the Gemara of various methods that were used in an attempt to cure tzefidna were, apparently, attempts to make up the lack of this vitamin by ingesting it in a concentrated manner.