The use of the 'Jericho Tyrus' in theriac: A case study in the history of the exchanges of medical knowledge between Western Europe and the Realm of Islam in the middle ages

The question of whether, or to what extent, the Latin East was an arena in which medical knowledge was exchanged has been raised by several historians. (1) However, very little has been done to explore the communication of actual pieces of information between the sides and its impact on western medicine. The present article aims to study in a very detailed way the exchange of just such an element--though one of considerable importance--as a test case in this wide field. We shall trace the process in which knowledge concerning a Syrian serpent, referred to as tyrus, and used in the composition of the famous theriac, reached the West through Latins who visited the Holy Land, and examine the reception and impact of that information in the West. We shall also see how this information entered the corpus of learned western medicine in a manner that complemented knowledge which already circulated in the West, thanks to Latin translations of Arabic works. As will be shown, this element of knowledge proved significant for centuries, not only from a medical point of view but also from that of commerce. Finally it will be suggested that it is highly probable that, with the use of the proper source material, numerous cases, similar to that which is presented below, might be revealed. As has already been stated, the test case with which we shall be concerned here has to do with a component of theriac, one of the best-known medieval recipes, if not the best known. The origins of this remedy go back to the ancient period when it was specifically meant to counteract the bites of venomous creatures. (2) It seems to have been first invented in the fourth or third centuries BC, but it is unclear by whom. (3) Four centuries later, Andromachus, Nero's physician, was the first to produce a theriac which included viper's flesh. (4) Both Pliny and Galen devoted considerable attention to this remedy, adding to its popularity. Thus, in classical times, the remedy called theriac was well known and, in some of its versions, included snake flesh. It is with the transmission of information regarding the type of snake to be used in theriac that this article is concerned. (5) Exchanges of knowledge in Outremer concerning the 'Jericho tyrus' Jacques de Vitry, Acre's famous bishop (1216-25), includes in his Historia orientalis the following comments: (6) In other words, in the Jericho region, one can find a snake called tyr, from which theriac, referred to here as tyriaca, is made. Evidence from the Frankish period shows that Jacques was not the only Latin to notice the importance of the Jericho region with regard to the snakes from which theriac was produced. (7) The Chronique d'Ernoul, written around 1231, says, discussing the environs of Jericho, that 'pries de celle cite a une gastine qui est toute plaine de serpens. La prent on les serpens dont on fait le triacle' ('Near that city there is a gastine [a deserted settlement], which is...