The doctrine of sympathy and antipathy, and more especially the latter half of it, was of immense value in mediæval medicine. As an example of sympathy we may instance the affection that was held to exist between the goat and the partridge; hence for whatever one of them was a remedy the other became equally available. The prescriptions were interchangeable, and one used one or the other in full faith that either was equally valuable, as indeed might very possibly be the case. As examples of the antipathetic treatment, one may instance the following:—“The Ape of all things cannot abide a Snail; now the Ape is a drunken beast, for they are wont to take an Ape by making him drunk and a Snail well wash’d is a remedy against drunkenesse. The Wolf is afraid of the Urchin; thence if we wash our mouth and throat with Urchin’s blood it will make our voice shrill, though before it were hoarse and dull like a Wolves voice. The Hart and the Serpent are at continuall enemity; the Serpent as soon as he seeth the Hart gets him into his hole, but the Hart draws him out again with the breath of his nostrils and devours him; hence it is that the fat and the blood of Harts, and the stones that grow in their eyes, are ministered as fit remedies against the biting and stinging of Serpents. Likewise the breath of Elephants draws Serpents out of their dens, and therefore the members of Elephants burned, drive away Serpents. So also the crowing of a Cock affrights the Basilisk, and he fights with Serpents to defend his hens, hence the broth of a Cock is good remedy against the poison of Serpents. The Stellion, which is a beast like a Lyzard, is an enemy to the Scorpions, and therefore the Oyle of him being purified is good to anoint the place which is stricken by the Scorpion. A Swine eats up a Salamander without danger, and is good against the poison thereof.” All these and many other hints of like value may be found in the pages of Porta.