SKETCH OF JOSEPH LEIDY. 689 



it and Trichina spiralis which he had met with in several human sub- 

 jects in the dissecting-room, since attention had been directed to it 

 by Mr. Hilton and Professor Owen. Leuckart afterward acknowl- 

 edged that he was indebted to this communication for his success in 

 tracing the development of trichina in the hog and man. 



In September, 1847, he published his first paleontological paper, en- 

 titled " On the Fossil Horse of America," in the " Proceedings " of the 

 Academy. The existence of remains of extinct horses on the Ameri- 

 can Continent had been regarded with incredulity, in consequence of 

 the entire disappearance of these animals in after-ages. The paper 

 consists of descriptions and figures of specimens contained in the Mu- 

 seum of the Academy of Natural Sciences of Philadelphia, some of 

 which the author regarded as belonging to the South American form, 

 described by Owen under the name JEJquns curvidens, and others as in- 

 dicating a new species, for which he proposed the name Equus Ameri- 

 canus. 



His investigations on the development of cartilage-cells, the struc- 

 ture of the liver, of the nettling organs in hydra, the presence of the 

 first indication of muscular fiber in the gregarines, the discovery of 

 the eye in the perfect condition of the cirrhopoda, together with de- 

 scriptions of many new forms of entozoa and entophita, miscellaneous 

 anatomical and zoological notes, and a continuous series of papers 

 entitled " Helminth ological Contributions," enriched the pages of the 

 " Proceedings " of the Academy during the next four or five years. 

 His elaborate memoir on the " Anatomy of Corydalus Cornutus in its 

 Three Stages of Existence," published in the " Memoirs of the Ameri- 

 can Academy of Arts and Sciences," and his beautifully illustrated 

 monograph entitled " A Flora and Fauna within Living Animals," 

 issued as part of the fifth volume of the Smithsonian contributions to 

 knowledge, merit special mention. 



These communications, laboriously prepared as many of them 

 were, did not, however, indicate the full extent of Dr. Leidy's indus- 

 try. Since the publication of his paper on the fossil horses of Amer- 

 ica, much of his time had been occupied in the study of the vertebrate 

 fossils in the museum of the Academy, or which were brought to his 

 notice from time to time by collectors. Long before the active explo- 

 ration of the West had added so immensely to our knowledge of the 

 extinct fauna of that region, he had determined the former existence, 

 in a tropical climate on our western slope, of the lion, the tiger, the 

 camel, the horse, the rhinoceros, and many other forms having no 

 immediate existing representatives. 



In 1853 the Smithsonian Institution published his memoir on the 

 extinct species of American ox, and in the following year the elaborate 

 "Ancient Fauna of Nebraska." Other paleontological papers were 

 published in the " Transactions of the American Philosophical Soci- 

 ety," and many new genera and species were announced in the " Pro- 

 TOL. xvn. 44 



