Ɛpsilon

To Joseph Lister   7 October 1878

down. | beckenham. kent.

Oct. 7. 1878.

My Dear Sir,

As this note requires no answer I will not apologize for making a small suggestion to you. I believe that you are still continuing your most valuable observations on Bacteria and their allies.1 Now it seems to me probable (or at least worth a trial) that Benzoic acid would be a most deadly poison to them.2 I think so because a minute dose of a solution of 1 part of the acid to 437 of water, when absorbed by the glands of Drosera, killed the protoplasm within them in a surprising manner. The glands presented in 12 min. the same white appearance as if the whole plant had been immersed in boiling water.— This is described in my Insectivorous Plants, p. 195.

I have been told that you employ borax as a disinfectant; and if this is so and it depends on the destruction of Bacteria, it is odd that Boracic Acid was not in the least injurious to Drosera.3

Pray forgive me for troubling you, if my suggestion appears to you useless; I remain with the highest respect, | Yours faithfully, | charles darwin.

1
CD had followed Lister’s research on bacteria and germ theory; Lister was highly critical of the theory of spontaneous generation (see Correspondence vol. 23, letter to J. S. Burdon Sanderson, 16 July 1875 and n. 3).
2
In Insectivorous plants, p. 197, CD noted his surprise that a weak solution of benzoic acid was highly poisonous to Drosera (sundew): ‘for I am informed that it produces no marked effect on the animal economy’. CD concluded that this and other ‘innocuous acids’ must act on elements of the plant that were ‘in no way analogous to the nerve-cells of animals’ (ibid., p. 223). Ernst Salkowski had discovered the antiseptic properties of benzoic acid in experiments performed in 1875; he found bacteria became immobile after coming in contact with the acid and their growth was inhibited (Salkowski 1875, p. 298).
3
CD had found that although a weak solution of boracic (boric) acid caused inflection of the leaves of Drosera, it was not toxic (Insectivorous plants, p. 191). Borax (sodium borate) is the sodium salt of boracic acid (hydrogen borate). Lister had described his use of boracic acid in the treatment of infection and wounds in the Lancet, 1 May 1875, pp. 603–5, and 22 May 1875, pp. 717–19.

Please cite as “DCP-LETT-11719A,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-11719A