Current Advances and Concepts in 
Virology * 
[With 4 plates] 
THESE VERY WEE ANIMALS 
“THE FOURTH sorT of little animals, which drifted among the three 
sorts aforesaid, were incredibly small; nay, so small, in my sight, that 
I judged that even if 100 of these very wee animals lay stretched out 
one against another, they could not reach to the length of a grain of 
coarse sand. ...” This quotation is attributed to Anton van Leeu- 
wenhoek, a Dutch linen draper, who was the father of microscopy and 
probably the first to see bacteria (1).? 
Many years later, attempts were made to remove these very wee 
animals. Cotton plugs and porous unburnt clay were used, and, in 
1877, Pasteur employed plaster of paris to separate anthrax bacilli 
from their containing fluids. 
In 1891, Nordtmeyer introduced a new filter medium made of com- 
pressed infusorial earth known as Kieselguhr. The filtering capabil- 
ities of this substance were noticed because the ground water in the 
Kieselouhr mine in Unterluss (Hannover) was of a clear blue color. 
The filter of Kieseleuhr, which is still used today, was called “Berke- 
feld,” after the owner of the mine. These filters are capable of hold- 
ing back the smallest bacteria, and fluids which have passed through 
them are bacteriologically sterile. Yet, infections may be produced 
by such sterile fluids because the causative agents—viruses—have 
filter-passing ability as a typical characteristic. 
Actually, the first scientific demonstration of the existence of a 
virus disease must be accredited to Ivanovski, a Russian botanist, who, 
in 1892, was investigating a disease of the tobacco plant known as 
tobacco mosaic. This worker extracted some of the sap from a dis- 
eased plant and passed it through a fine filter made of unglazed porce- 
lain. He then discovered that the filtrate, although sparkling clear 
1 Prepared by members of the medical staff, Lilly Research Laboratories. Reprinted by 
permission from Physician’s Bulletin, vol. 24, No. 38, Apr. 1, 1959, published by Eli Lilly & 
Co., S. O. Waife, M.D., editor. 
2 Numbers in parentheses indicate references at end of text. 
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