The weasel is a dirty animal that must not be eaten. It conceives at the mouth and gives birth through the ear (though some say it is the other way around). If the birth takes place through the right ear, the offspring will be male; if it is through the left ear, a female will be born. There are two types of weasel; one lives in the woods and the other in houses. Weasels chase mice and snakes. The cleverness of weasels is shown by the way they move their young from place to place. They are also skilled in medicine and can revive their young if they are killed.

The weasel is the enemy of the basilisk and is the only animal that can kill one.

The weasel appears under the name gali in the medieval encyclopedias of Thomas of Cantimpré and Jacob van Maerlant. It is described as a bold animal that fights with snakes, and when it has defeated them, it eats them, and soon afterwards it eats the herb rue that counters snake venom. It kills snakes because they eat mice, and the gali itself likes to eat mice. This animal enters its burrows from the north or from the south, so as not to be tired by the wind against it. It also appears under the name guesseles, where it is described as an animal that often lives around water; is brown on the back, white on the belly; makes its dwellings in the earth; and produces dung that smells like musk.

Weasels signify people who willing hear the seed of the divine word, but then do nothing with what they have heard.

The dung of the weasel smells of musk; it produces bad and good dung, but only leaves the good dung out where people can collect it. A weasel's flesh cooked in olive oil until it is dissolved, the oil when strained through a cloth is effective against arthritis, stiff nerves, rheumatism and scrofula. Its blood can cure epilepsy. Its gall is an antidote for viper poison. Its ash mixed with water is effective against the sleeping sickness caused by snake bites.

Hildegard von Bingen says, "Also, dry the weasel’s heart, set it in thin wax, and when you have a headache place the wax with the heart in it in your ear for a little while, so its heat might enter your head. Your head will be better. And, if you begin to go deaf in one ear, put the wax-encased heart on that ear until its heat reaches the inside of the ear, and you will recover your hearing. Also, cut the weasel’s head off and dry the rest of its body, in two pieces, in the sun or over the fire. Then sew them separately into a belt made of any kind of leather, so the first piece is placed over your umbilicus, the other piece over both your sides. Always gird yourself with that belt against your bare skin. It will strengthen you and make you safe and robust, so that gicht [gout] will not trouble you." (Throop translation)