On Contagium Vivum Fluidum [Virology lessons]

"In order to find the truth always go back to the source" My quote 2022

So, the concept of viruses as a seperate new biological entity that is not being able to grow independently but uses another organism belongs to Beijerinck.

He presented his findings on the tobacco plant "virus" or Contagium Vivum Fluidum before the Dutch Royal Academy on the 26th of November 1898.

Virology as a science is based on a botanologist's findings.

The major observations (I cannot get hold of the original paper plus it is Dutch !) were as follows:

1 Crude extracts from diseased plants passing through porcelain filter candles do not show bacterial growth during three months of storage, but remain infective. Subsequent plant inoculation by injection readily leads to infection and reproduction of the characteristic symptoms.

2 Unlike bacteria, the infectious agent diluses laterally into agar for at least 2 mm.

3 The agent multiplies in plants, as shown by serial transfers from plant to plant, and cannot be a toxin. [I do not underatnd how he came to think this or what was his evidence]

4 The agent multiplies only in actively growing tissues. It is not able to grow by itself but is carried away by the growth of dividing cells where multiplication in the living protoplasm is enormous. [I do not underatnd how he came to think this or what was his evidence]

5 Transport is `through the phloem', upwards and downwards according to laws directing the movement of nutrients; in stems it is primarily vertical with little lateral spread.

6 The agent resembles living cells in that it is killed at 90 8C.

7 The agent may be dried in infected leaves (in a herbarium) and in filter paper soaked in infectious sap.

8 The agent may remain in dry soil during winter and infect plants from the soil; it can also be transferred in potting soil.

9 The agent retains infectivity after alcohol precipitation from sap and subsequent desiccation at 40 8C.

Beijerinck's conclusion, therefore, was that infection is not due to a microbe (a contagium fixum; Beijerinck 1898a), but to a non-corpuscular (that is, non-cellular) entity which he named contagium vivum fluidum.

NB: until that time the term virus was used to denote a poisonous entity of sorts.

Reference:

Bos L. Beijerinck's work on tobacco mosaic virus: historical context and legacy. Philos Trans R Soc Lond B Biol Sci. 1999;354(1383):675-685. doi:10.1098/rstb.1999.0420