BIOGRAPHICAL NOTICE 
OF 
JOSEPH LEIDY. 
BY 
THOMAS GEORGE LEE. 
[Reprinted from the Proceedings of the American Academy 
of Arts and Sciences, Vol. XXVII.] JOSEPH LEIDY. 
Joseph Leidy, a member of this Academy since May 30, 1848, 
died, after a brief illness, at his residence in Philadelphia, Pa., on 
April 30, 1891. His ancestors were of French-German descent, and 
came to this country as missionaries. His father, Philip Leidy, was 
born in Montgomery Co., Pa., in 1791, and married Catherine Melick. 
Joseph Leidy was the third child by this marriage, and was born in 
Philadelphia, September 9, 1823. His mother died when he was a 
year and a half old ; later his father married Christiana Melick, a sister 
of his first wife. She proved to be an admirable mother to Joseph, and 
to her watchful care and direction is due in great measure his choice 
of life work. His early education was obtained in private schools, and 
even during this period he manifested a marked inclination toward the 
study of natural history, being particularly interested in plants and 
minerals. After hearing a lecture on these subjects, given by an itin- 
erant lecturer in the school house, young Leidy procured text-books, 
and began the systematic study of botany and mineralogy. From an 
early age he showed great skill in drawing. This power became so 
marked that at the age of sixteen his father removed him from school 
with the intention of having him become an artist. At this period he 
spent much of his time in a wholesale drug-store near his home; here 438 
JOSEPH LEIDY. 
he made such good use of the opportunity for studying the nature of 
various drugs, and in compounding medicines, that the proprietor 
recommended the boy as being competent to take charge temporarily 
of the retail drug store of a customer. 
This success led him to consider seriously the advisability of becom- 
ing an apothecary. All this time he had continued his natural history 
studies, and by the dissection of a few cats, chickens, etc., he devel- 
oped such an interest in comparative anatomy that his step-mother de- 
cided that Joseph should become neither an artist nor a druggist, but 
a physician. Having decided upon the study of medicine, he gave his 
first year to the study of practical anatomy, and under the preceptor- 
ship of Doctors Paul B. Goddard and James McClintock took three 
full courses of medical lectures at the University of Pennsylvania, re- 
ceiving in the spring of 1844 the degree of Doctor of Medicine, his 
thesis being an admirable essay on " The Comparative Anatomy of the 
Eye of Vertebrated Animals." He now entered upon the active prac- 
tice of medicine, and at the same time was appointed Assistant to the 
Chair of Chemistry in the University. He also assisted Dr. Goddard, 
the Demonstrator of Anatomy. 
At the end of two years he gave up the practice of medicine in order 
that he might devote himself entirely to study and teaching. His skill 
in anatomy was so great that he was appointed Prosector to the Chair 
of Anatomy by Professor Horner. In 1846 he was elected Demonstra- 
tor of Anatomy in the Franklin Medical College, which position he held 
for one year and then resigned to return to the University, where 
he was again associated with Professor Horner. He also gave private 
courses in anatomy. In the spring of 1848 he accompanied Dr. Hor- 
ner to Europe, in the fall gave a course of lectures on Histology, and 
in the following spring lectured on Physiology at the Medical In- 
stitute. This constant application affected his health so that he was 
obliged to abandon all work for some months. In 1850 he went abroad 
with Dr. George B. Wood to make a collection of models, drawings, 
etc., with which to illustrate Dr. Wood's course of lectures on Medi- 
cine. This trip was of very great value to Dr. Leidy, as it enabled 
him to visit all the great museums of Europe, and to make the ac- 
quaintance of such distinguished anatomists and physiologists as Owen, 
Majendie, Hyrtl, Johannes Muller, and others. He returned from 
this trip with renewed health, and in 1851 resumed his anatomical 
work at the University. 
During this year he was elected a member of the College of Phy- 
sicians and appointed Pathologist to St. Joseph's Hospital. In the JOSEPH LEIDY. 
439 
winter of 1852 Professor Horner through ill health was unable to con- 
tinue his lectures on anatomy, and at his request Dr. Leidy was ap- 
pointed as his substitute. After the death of Dr. Horner, he was, in 
May, 1858, appointed Professor of Anatomy, which position he held 
until his death. 
During the ten years preceding his appointment to the Chair of 
Anatomy, in addition to his regular duties, Dr. Leidy found time to 
continue his scientific studies. In 1844, the year of his graduation, he 
contributed to Amos Binney's monograph of the Mollusca an admira- 
ble introductory chapter on the " Special Anatomy of the Terrestrial 
Mollusks of the United States," together with sixteen beautifully 
executed plates illustrating the anatomy of thirty-eight species of Mol- 
lusca. In 1845 he was elected a member of the Boston Society of Nat- 
ural History, and of the Philadelphia Academy of Natural Sciences. 
With the latter institution he was constantly associated during the rest 
of his life, being successively Librarian, a Curator, and from 1847 
chairman of the Board of Curators. With his natural modesty, he 
many times refused the office of President, but finally in 1881 accepted 
it, and remained President of the Academy to the end of his life. 
The Proceedings of the Academy furnish a brilliant memorial of his 
great attainments in various branches of natural science, as they con- 
tain several hundred valuable contributions to zoology, paleontology, 
comparative, human, and microscopic anatomy, botany, and mineralogy. 
While he never regarded himself as an authority, and published but 
little upon mineralogy and botany, his knowledge of these subjects was 
that of a specialist. This was well shown by the frequent verbal com- 
munications which he made as Curator in calling the attention of the 
Academy to additions to the mineralogical cabinet; his knowledge of 
gems and their values was also very extensive. The very fine and 
valuable mineralogical collection made by him has recently been pur- 
chased by the government, and will be placed in the National Museum 
in Washington. 
His familiarity with plants was also frequently noted at the meet- 
ings of the Academy and elsewhere. The herbarium which he gave 
the Biological Department of the University of Pennsylvania contains 
over 1,500 species which were collected and determined by himself. 
In zoology he gave especial attention to invertebrate forms; and 
while paying particular attention to parasites and Protozoa, he made 
valuable contributions to our knowledge of many other groups. As 
early as 1846 he observed minute specks in some pork that had been 
cooked, which, when examined with a microscope, were found to be a 440 
JOSEPH LEIDY. 
species of Trichina. In his communication on this discovery he stated 
that this species was apparently the same as that found by Owen and 
himself in man. The famous zoologist Leuckart, who afterward 
worked out the life history of Trichina spiralis, acknowledged his 
indebtedness to this observation of Dr. Leidy. In 1853 appeared the 
" Fauna and Flora within Living Animals," a beautifully illustrated 
and valuable work, which showed very clearly the wide range of ani- 
mal and vegetable parasites which are to be found in the alimen- 
tary canals of small animals, as beetles, centipedes, cockroaches, etc. 
This paper is also interesting as having expressed ideas closely re- 
sembling in many respects those advanced a few years later by Darwin 
in his " Origin of Species." 
Dr. Leidy's contributions to helminthology were numerous, and of 
such merit as to render him the highest authority on this subject in 
this country, and the peer of such men as Leuckart, Cobbald, and 
Diesing. His papers upon various insects and their life histories gave 
evidence of his familiarity with entomology. In 1848 he made the 
discovery of the presence of eyes in a species of Balanus, which led 
Darwin to look for them in other members of this group. 
Dr. Leidy was particularly interested in the very lowest forms of 
animal life. In addition to many smaller papers, he gathered together 
in the magnificent monograph, " Fresh Water Rhizopods of North 
America," the results of many years' study. The numerous plates 
illustrating this volume are splendid examples of his marvellous ar- 
tistic skill. Among the first persons in this country to use the micro- 
scope, he early established his ability as a histologist by his valuable 
paper, " Researches into the Comparative Structure of the Liver " 
(1848). The views advanced in this paper, though not generally 
accepted at the time, have since been largely confirmed by embryo- 
logical research. 
In 1861, he published "An Elementary Text-book on Human Anat- 
omy," in which the noteworthy attempt was made to substitute an 
English terminology with foot-note references for the cumbersome and 
perplexing anatomical nomenclature in common use. This was quite 
successful, and was carried to still greater perfection in the second 
edition of this book, which was finished a short time before his death. 
This anatomy is unexcelled by any in the language for accuracy of 
detail and clearness of expression. Dr. Leidy's other papers upon 
vertebrate anatomy exhibit the careful work and clear judgment so 
characteristic of all that he did, and the many new facts presented by 
him have been almost always confirmed by later investigators. No 441 
JOSEPH LEIDY. 
one was more ready than himself to acknowledge and correct an error 
when found. 
There remains still another field of scientific research in which Dr. 
Leidy achieved a world-wide reputation, namely, paleontology. His 
first paper on this subject appeared in 1847, "The Fossil Horse of 
America." Although he was almost the first person in this country 
to take up the subject of vertebrate paleontology, and had at first very 
meagre opportunities for the study of the comparative osteology of 
many recent forms, he produced in the next few years a series of bril- 
liant papers, which entitle him to be considered as the equal of any 
paleontologist produced by this country or Europe. 
The following are among the more prominent of his many contri- 
butions to this subject: "Ancient Fauna of Nebraska," 1853; "Me- 
moir of the Extinct Sloth Tribe of North America," 1855 ; " Cretaceous 
Reptiles of the United States," 1865 ; " Extinct Mammalian Fauna of 
Dakota and Nebraska, together with a Synopsis of the Mammalian 
Remains of North America," 1869; "Contributions to the Extinct 
Vertebrate Fauna of the Western Territories," 1873 ; "Description of 
Vertebrate Remains from the Phosphate Beds of South Carolina," 
1877. 
The interest aroused by these wonderful discoveries led others 
to enter this field of investigation. Great rivalry and many acrimo- 
nious disputes regarding priority and nomenclature arose, so that, 
rather than become entangled in controversy, Dr. Leidy gave up 
this work in which he had achieved such success, and devoted him- 
self to other fields of scientific work. He however contributed from 
time to time small paleontological papers, the last appearing in May, 
1890. 
Dr. Leidy acted as surgeon to the Satterlee Military Hospital dur- 
ing the war, and the results of the many interesting autopsies made by 
him are recorded in the "Medical and Surgical History of the War." 
He was elected a member of the National Academy of Science, in 
1863, at the time of its organization. In 1871 he was appointed Pro- 
fessor of Natural History in Swarthmore College; and in 1884, upon 
the establishment of the Biological Department of the University of 
Pennsylvania, he was appointed Professor of Zoology and Comparative 
Anatomy. In 1885 he was elected President of the Wagner Free 
Institute of Science in Philadelphia; and in 1889, at the time of its 
organization, President of the Association of American Anatomists. 
Many honors, both at home and abroad, were conferred upon this 
distinguished naturalist.. In 1886 Harvard University conferred upon 442 
him the degree of Doctor of Laws. The Boston Society of Natural 
History awarded to him, in 1879, the Walker grand prize of $500. 
which in this instance was raised to $1,000 as a special recognition of 
his contributions to science. In 1879 he received a prize from the 
Royal Microscopical Society. The Geological Society of London 
awarded to him, in 1884, the Sir Charles Lyell medal for his pale- 
ontological researches ; and in 1888 he received from the Paris Acad- 
emy of Sciences the Cuvier medal for his work in biology. In the 
period from 1845 to 1887 he was elected honorary member by over 
forty of the learned societies of Europe and this country. 
It is impossible in this brief notice to do more than indicate in the 
most general manner the life work of this great man, which covers 
almost a half-century. In this period his contributions to natural his- 
tory number nearly one thousand, ranging from short papers to large 
illustrated volumes, which probably contain fewer errors of fact and 
interpretation than those of any other writer on so many and such 
varied subjects. His personal character was in perfect accord with his 
wonderful mental attainments. He was remarkable for an entire ab- 
sence of self-assertion or conceit. Wholly unselfish, his amiability and 
charming simplicity of manner rendered him a delightful companion, 
always approachable and ready to aid a student by advice or expla- 
nation. In the lecture-room his clear and concise descriptions formed 
word pictures rivalling in distinctness his admirable blackboard illus- 
trations. He was as incapable of deceit as he was modest, and sub- 
mitted to imposition rather than enter into controversy. His long life 
was devoted to science for the advancement of knowledge, and with- 
out thought of gain or personal glory. 
Notwithstanding failing health during the last few months, Dr. 
Leidy still continued his active work ; and thus, as he desired, with 
his shoulder to the wheel, one of America's greatest naturalists passed 
away.