The wonderful lives of Joseph Leidy (1823-1891).

Except in Philadelphia where his greater-than-lifesize statue adorns the entrance to the great Academy of Natural Sciences, and the University of Pennsylvania biology department is housed in the building that bears his name, Joseph Leidy (1823–1891) is virtually unknown today. Yet his myriad contributions to science are important and entirely trustworthy. Although Leidy was one of America’s greatest naturalists, his biographer, Leonard Warren [9], found it necessary to devote an entire chapter to Leidy’s lack of reputation (Chapter 16, “The eclipse of Leidy”). In his fascinating new book of great interest to microbiology Warren writes (p. 251):“In the course of his career, Leidy examined tens of thousands of organic forms and described and named over a thousand new ones —fossils, protozoa [sic], parasites of many forms, insects, molluscs, and helminths—a feat virtually without precedent. What did this busy investigator have in mind? Without question he gathered his knowledge because it gave him pleasure. ” A precise tabulation of Leidy’s contributions was published more than 100 years after his death [2]. In 1923, more than 30 years after he died, Leidy was commemorated by one of his many admirers: “Dr. Leidy’s vision covered all nature, from the mammals and gigantic reptiles of the past to the world of small things which are revealed to the eye by the highest powers of the microscope; and I never knew anyone who carried on so varied a series of observations without confusion. ” Leidy is considered “the founder of American vertebrate paleontology, parasitology, and protozoology and America’s foremost anatomist, the person who revealed the power and versatility of the microscope. ” (p. 252 [9]). Not only was he the first in North America to discover the dinosaur but he was the first in the world to discern what wooddwelling “white ants” (termites) eat. His impatient curiosity led him to investigate the dwellers of a decaying log in New Jersey. He reported that a squeeze of intestinal fluid revealed (“like citizens leaving a crowded meeting hall”) a flurry of live “parasites” [5]. When he documented the bacilli, trichomonads, prysonymphids and hypermastigotes that exuded from the “termes” hindgut he named his 1850 paper, “On the existence of endophyta in healthy animals as a natural condition” [4]. Leidy discovered benign, indeed requisite cellulolytic protists responsible for the ingestion of wood by termites. He was also the first to recognize the Trichinella nematode as the cause of trichinosis caused by undercooked pork. He gave binomial names in use today to hundreds of New World animals, fungi, protists and bacteria. Leidy’s descriptions and drawings of amoebae (rhizopods) are still without parallel. “A driven man, he seemed possessed by a sustained frenzy,” or as one acquaintance put it, “absorbed in his new discoveries of rhizopods in the cracks of the city pavements” (p. 251 [9]). “How can life be tiresome as long as there is still a new rhizopod undescribed? ” (p. VI [9]) is the way Leidy himself stated his passion in his sparse and appropriate style. Disdaining speculation, Leidy always remained close to his original material. None of his observations has been shown to be mistaken or exaggerated. He may also be claimed Andrew Wier Lynn Margulis