LS (the body written in the hand of Darwin’s son), four pages on two adjoining sheets, 5 x 8, Down, Beckenham, Kent letterhead, January 3, 1878. Letter to a gentleman, in part: “Dr. Sanderson showed me some admirable photographs on glass by Dr. Koch of the organisms which cause splenic fever; but your letter & the valuable work which you kindly gave me make the case much clearer to me. I well remember saying to myself between 20 & 30 years ago, that if ever the origin of any infectious disease could be proved, it would be the greatest triumph to science & now I rejoice to have seen the triumph. With respect to the filaments of Dipsacus, I do not for a minute put my judgement on a par with yours of that of deBary, but my son has lately made some observations which incline me very strongly to believe the filaments consist of living matter of the nature protoplasm. Hearing from Dr. Sanderson, that thymol has a fatal effect on low organisms, he tried solution…which cause contractions of the filaments. On the other hand, 1/2% solution of carbolic acid does not cause contraction, 1% does so, this agrees with several observers who find, I believe, that 1/2% carbolic solution is not poisonous (F. microzumes). My son finds that strong solutions of NaCl cause contractions but not death as the filaments recover themselves in water & do not swell up into bladders as they do after poison. This agrees with deVries’ work on the ‘plasmalysis’ of cells.” In fine condition. Accompanied by an unsigned carte-de-visite photo of Darwin by Elliott & Fry.
As Darwin was at this stage of his career involved mainly with botanical research—he would later observe that he spent ‘the whole of this last year [1878]...on the circumnutating Movements of plants & bloom’—the content of the present letter, related to the emerging field of microbiology is highly unusual and significant. These advances would soon revolutionize the understanding and treatment of infectious diseases.
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