LEIDY, JOSEPH (1823-1891), American scientist, was born at Philadelphia, Pa., on Sept. 9, 1823. After receiving an early education in private schools he entered the University of Pennsylvania and in 1844 graduated in medicine. He soon after became librarian and a curator at the Academy of Natural Sci ences of Philadelphia, and in 1847 was made chairman of the board of curators, which position he held for a period of 44 years. In 1853 he was appointed professor of anatomy at the University of Pennsylvania, which position he held until his death, becoming director of the biological department in 1884. In addition to these duties he was professor of natural history at Swarthmore college from 1871 also until his death. He won distinction as an anatom ist, especially in the field of comparative anatomy. His Elementary Treatise on Human Anatomy (1861; rev. and enl., 1889) was for many years the classic American text-book on the subject. His Researches into the Comparative Anatomy of the Liver (1848) was the first thorough study of that organ. Leidy spent much time in microscopical study of the lower forms of life. His book A Flora and Fauna Within Living Animals (1853) was the first important study of the parasites of the alimentary canal. Leidy's discovery of Trichina spiralis in pork led to Leuckart's discovery of the cause and mode of preventing trichinosis in man. In 1886 Leidy expressed his opinion that hookworm was the cause of pernicious anemia in the United States. He also became the chief American authority of his time on protozoa. His Fresh Water Rhizopods of North America (1879) is still a standard work. This, and many others of his books are illustrated by his own drawings, noted for their delicate accuracy, especially in micro scopical studies. His Synopsis of Entozoa, described and named
more than i oo new species.
It was as a vertebrate palaeontologist, however, that Leidy won his chief fame. Before his time there were but a few scattered papers on the subject in America, and the discovery of new fossil deposits in the western States offered him an unparalleled oppor tunity to lay the foundation of American palaeontology, his knowledge of comparative anatomy being his chief aid in the work. His Ancient Fauna of Nebraska (1853) was the most important contribution to the subject in America up to that time. He followed this with monographs on the extinct sloth tribc, the extinct ox, horse, etc., and in 1865 published Cretaceous Reptiles of the United States. All the fossils of the F. V. Hayden Expe dition in the Rocky Mountains (1853-66) were given to Leidy for determination, the results appearing in Extinct Mammalian Fauna of Dakota and Nebraska (1869), which contained many species and genera unknown to science, and others hitherto not known to have existed on the American continent. The book is described by H. F. Osborn as "with the possible exception of Cope's Tertidry Vertebrates, the most important palaeontological work which America has produced." The discovery of Eocene material in Wyoming and Oregon beds, geologically older than the Nebraska and Dakota beds, provided the material for Leidy's last major palaeontological work, Contributions to the Extinct Vertebrate Fauna of the Western Territories (1873). His death occurred at Philadelphia on April 3o, 1891.