The Dutch Scientist, Antonie van Leeuwenhoek (1632–1723), was best known for his pioneering works in establishing Microbiology as a scientific discipline. He examined his own stool in 1681 and was reported to have penned what he saw:
“All these described particles lay in a clear transparent medium, in
which I have at times seen very prettily moving animalcules, some rather
larger, others somewhat smaller than a blood corpuscle, and all of one and
the same structure. Their bodies were somewhat longer than broad, and
their belly, which was flattened, provided with several feet, with which they
made such a movement through the clear medium....... But although they
made a rapid movement with their feet, yet they made but slow progress."
(Dobell, 1920)1 [Cited by Erlandsen S.L. & Feely D.E. (19842)]
This description much resembles that of the intestinal protozoa Giardia lamblia. Microscopy has made an excellent contribution to the progress of science and in an era of technological advancement in the laboratory investigation of parasitic diseases, Microscopy continues to be regarded as the gold standard for definitive diagnosis.
1 Dobell, C., 1920, The discovery of the intestinal protozoa of man, Proc. R. Soc. Med. 13:1–15.
2 Erlandsen S.L., Feely D.E. (1984). Trophozoite Motility and the Mechanism of Attachment. In: Erlandsen S.L., Meyer E.A. (eds) Giardia and Giardiasis. Springer, Boston, MA