JOHN MARCA, an eminent Italian physician, was born at Rome in 1654. From his earlier years he had a predilection for natural history, and studied botany, chemistry, anatomy, and medicine, with great assiduity. In 1688 Innocent XI. appointed him his physician and private chamberlain, notwithstanding his youth; and Cardinal Altieri Camerlinga made him vicar for the installation of doctors in physic, which Clement XI. gave him as long as he lived, at the same time continuing to him the appointments conferred on him by his predecessor. He died in 1710, after giving his fine library of more than twenty thousand volumes to the Hospital of the Holy Ghost for the use of the public. This noble benefaction was opened in 1716, in the presence of the pope and most of the cardinals. He wrote many works, which are esteemed, the principal of which were collected and printed at Geneva in 1718, in two vols. 4to.