Reply To: A Hello to Virology
At the same time, Friedrich Loeffler and Paul Frosch were conducting experiments on foot-and-mouth disease with the following findings (this according to secondary sources, as I have yet to find the original papers):
“1. The disease can be artificially transferred in lymph from epidermal vesicles; bacteria that these sometimes contain do not reproduce the disease.
2. Lymph, filtered for isolation of an agent responsible for immunity developing soon after infection, is still infectious.
3. The infectious agent cannot be grown in artificial media.
4. The filtrate does not contain a toxin responsible for the disease but `as yet undetectable disease agents so small that they were able to pass the filter pores retaining the smallest bacteria’ including those of Bacillus fluorescens previously added as a control.
5. The infectious agent must be so small that it would indeed escape visible detection by microscopy (according to calculations by Professor Abbe, Jena, about the limit of resolution of the microscope used).
6. The agent is not soluble but ‘corpuscular’ because it is retained by a one-pored Kitasato filter.”
I’d like to get back to foot-and-mouth disease later, but for now it is evident what the implications of these early studies were. These researchers had found minute pathogens, smaller than any bacterium, and they weren’t toxins. They also couldn’t proliferate without the help of living cells. Other than that, they really had no idea what a “virus” actually was.
This would be the case for decades. Enter the era of the “filterable virus”.
An excellent example of a paper typical for this time is given here:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2180297/