ions of the lens-makers. The
new knowledge clarified one very turbid medical pool and pointed the way
to the clarification of many others.

Almost at the same time that the Polish medical student was
demonstrating the itch mite in Paris, it chanced, curiously enough,
that another medical student, this time an Englishman, made an analogous
discovery of perhaps even greater importance. Indeed, this English
discovery in its initial stages slightly antedated the other, for it
was in 1833 that the student in question, James Paget, interne in St.
Bartholomew's Hospital, London, while dissecting the muscular tissues of
a human subject, found little specks of extraneous matter, which,
when taken to the professor of comparative anatomy, Richard Owen, were
ascertained, with the aid of the microscope, to be the cocoon of a
minute and hitherto unknown insect. Owen named the insect Trichina
spiralis. After the discovery was published it transpired that similar
specks had been observed by several earlier investigators, but no one
had previously suspected or, at any rate, demonstrated their nature. Nor
was the full story of the trichina made out for a long time after Owen's
discovery. It was not till 1847 that the American anatomist Dr. Joseph
Leidy found the cysts of trichina in the tissues of pork; and another
decade or so elapsed after that before German workers, chief among whom
were Leuckart, Virchow, and Zenker, proved that the parasite gets into
the human system through ingestion of infected pork, and that it causes
a definite set of symptoms of disease which hitherto had been mistaken
for rheumatism, typhoid fever, and other maladies. Then the medical
world was agog for a time over the subject of trichinosis; government
inspection of pork was established in some parts of Germany; American
pork was excluded altogether from France; and the whole subject thus
came prominently to public attention. But important as the trichina
parasite proved on its own account in the end, its greatest importance,
after all, was in the share it played in directing attention at the
time of its discovery in 1833 to the subject of microscopic parasites in
general.

The decade that followed that discovery was a time of great activity in
the study of microscopic organisms and microscopic tissues, and such
men as Ehrenberg and Henle and Bory Saint-Vincent and Kolliker and
Rokitansky and Remak and Dujardin were widening the bounds of knowledge
of this