This book features four significant papers selected to represent the historical background of plant pathology. These papers individually and collectively have made a profound and lasting influence on subsequent virus research and reasoning. This book includes three early papers on tobacco mosaic and one on infectious variegation.

This book presents four papers by scientists whose early work enhanced understanding of the origin and nature of virus diseases. Each paper provides a short biography of the author, followed by the classic paper

Early Papers on Tobacco Mosaic and Infectious Variegation

1. Concerning the Mosaic Disease of Tobacco, by Adolf Mayer:

The now commonly applied term for many virus diseases of plants, namely “mosaic,” was first introduced by Adolph Mayer in his 1886 paper, which is translated in this series. Mayer is also generally considered the first to prove the infectious nature of tobacco mosaic disease, which later became the first known filterable virus. Mayer attempted to filter the infectious agent and could find no microorganisms accountable for the disease by modern bacteriological technique; therefore, he suggested its similarity to enzymes. Nonetheless, he reasoned that the disease must be of bacterial origin. The stimulating effect of this contribution on later research can well be imagined.

2. Concerning the Mosaic Disease of the Tobacco Plant, by Dmitrii Ivanowski:

This short paper by Ivanowski, published in 1892, is perhaps the most widely recognized article in both the plant and the animal virus fields. In a few brief sentences, Ivanowski essentially states that he filtered the juice of mosaic-diseased tobacco plants through a Chamberland filter and that the filtrates remained unchanged (sterile) and reproduced the typical disease. This outcome is recognized as the first demonstration of a filterable infectious agent in plant, animal, or human pathology. Curiously enough, this paper is devoted largely to a disagreement with Adolf Mayer over the identity of two types of symptoms of disease on tobacco with respect to cause. The contention upheld by Ivanowski is now generally believed to be erroneous. Ivanowski is also well known for a later paper, published in 1903, in which he first described abnormal intracellular inclusions in tobacco mosaic, including protozoan-like inclusion bodies and the crystallike bodies now believed by some to be the virus particles.

3. Concerning a Contagium Vivum Fluidum as Cause of the Spot Disease of Tobacco Leaves, by Martinus W. Beijerinck:

Beijerinck’s 1898 paper is perhaps most widely known because of his “contagious living fluid” concept. This conception, along with the first application of the term virus (as contrasted with a poison or toxin or bacterial suspension), was not entirely new. Somewhat earlier, Pasteur had been confronted with similar issues with rabies, and the same year, Loeffler and Frosh had filtered the causative agent of foot and mouth disease of cattle and been concerned about what the substance might be and how it reproduced. Beijerinck’s experimental material, namely, tobacco mosaic (he used the names “spot-disease,” “albinism,” and “bunt”), was better adapted for fundamental studies, and he asked himself many questions, both practical and technical, which he attempted to answer using simple experimental methods. For example, he studied diffusion of the virus into agar as a measure of its corpuscular or noncorpuscular nature. His contagium vivum fluidum appears to come very close to the current concept of a protein molecule as representing the physical structure of a virus.

4. On the Etiology of Infectious Variegation, by Erwin Baur:

Baur’s 1904 paper was selected for translation not because of his interesting demonstrations on the transmissibility of infectious variegation by grafting but because of the emphatic manner in which he used his knowledge of infectious variegation to reason against the generally accepted belief that all infectious diseases were necessarily caused by parasitic organisms. Baur’s idea of a virus and its reproduction, not unlike that of Beijerinck, serves to emphasize that progress in the understanding of the origin and nature of a virus has not advanced far since 1904.