The So-Called "Invisible" Microbes. E. Roux. (Bulletin de L'Institut Pasteur, No. I, 1903.)
The hypothesis advanced by Pasteur in 1881, that the microbes of rabies were so small as to be invisible, has been frequently advanced to explain the failure to find the microbe in such diseases as small-pox, measles, scarlet-fever, syphilis, etc. Until the year 1898, the "invisible" microbes were purely speculative, but the last four years have given them a reality in a number of diseases. Roux, in the first installment of a review written for the new "Bulletin de L'Institut Pasteur", presents the methods used in demonstrating the existence of a few of these invisible microbes.
ABSTRACTS.. Arch Dermatol. 2003;139(5):569. doi:10.1001/archderm.139.5.569