The ancients attributed poisonous properties to certain bodies simply on account of their origin being mysterious and obscure, and many of these errors and traditions have been handed down for centuries. As an instance of this, the belief that diamond dust possessed deadly poisonous properties seems to have existed until recent times. Many mysterious deaths in the Middle Ages were attributed to it. There is little doubt that death might be caused by the mere mechanical effect of an insoluble powder of this kind, if it were possible to introduce it into the stomach in sufficient quantity, but powdered glass or sand would have the same effect as diamond dust, viz. in causing violent irritation of the stomach. Yet some of these old traditions have a substratum of fact. The poisonous properties of the toad have long been regarded as fabulous, but recent investigation has proved that the skin of a species of toad secretes a poison, similar in action to digitalis. The venom of the toad has had the reputation of possessing poisonous properties from a very early period, and was probably one of the earliest forms of animal poison known. The old tradition, that King John was poisoned by a Friar who dropped a toad into his wine, was regarded as a ridiculous fable until some years ago, when it was discovered that the skin of the toad secretes a body, the active principle of which, "phrynin," is a poison of considerable power. One of the most curious uses to which the toad has been put is recorded on a medical diploma now in the Library of Ferrara, which was granted to one Generoso Marini in 1642. Marini having made application for a Ferrarese diploma in medicine, the judges in whom the power of granting such degrees was invested, ordered him to exhibit some efficient proofs of his capability to practise the medical art. Marini at once agreed to comply with their demand, and the result is recorded in his diploma, which was discovered by Cittadella in the archives of Ferrara, and is translated as follows:--