John-Baptist Van, a leader of distinction in the chemical school of medicine, was born at Brussels in the year 1577, and descended of a noble family. He studied medicine at Louvain and some other places with so much avidity, that he had perused Hippocrates, Galen, and the Greek and Arabian physicians at a very period of life. When not more than 17 years of age, he read public lectures at Louvain, and was created M.D. in the year 1599 when only 22. Having, in 1609, married a wife who was both rich and noble, he retired with her to Vilvorde, where he practised as a physician without taking any fees, and was accustomed to boast of the thousands whom he cured every year, although his success in his own family was by no means great; for his eldest daughter died of a leprosy, and he lost two sons by the plague. He published a variety of works, by which he acquired very great reputation. He was invited to the court of Vienna by the emperor Rodolph, which he declined to accept. He died in the year 1644, in the 68th year of his age.

He was a man of acute genius, clear-sighted in detecting the mistakes of others, and extremely fond of forming hypotheses of his own, which were not always supported by conclusive arguments. He affirmed with boldness, was extremely credulous, and fond of such extravagant narrations as seemed to favour his own preconceived opinions. Perhaps his greatest foible was the liberal manner in which he praised himself, in reference to his own nostrums and pretended specifics. His ideas were far from being perspicuous, chiefly owing to his making use of terms and phrases which he never properly defined. He added much, however, to the stock of chemical facts at that time known, and paved the way to more interesting discoveries. He contributed more than any of his predecessors, to subvert the Galenical theory of humours and qualities, which he certainly combated with many forcible arguments. His theory of ferments was in a great measure espoused by Sylvius. His son Francis-Mercurius first published his works collectively in 1648; and although it cannot be denied that they abound with jargon and error, they contain many pertinent remarks, and much curious and interesting speculation.

a small town in the Netherlands, in Dutch Brabant, and capital of the district of Peeland, with a good castle. It is seated on the river Aa, in E. Long. 5° 37', N. Lat. 51° 31'.