Ɛpsilon

From W. H. Dallinger   29 June 1878

The Parsonage | Woolton. Liverpool

June 29. 1878.

Chas Darwin Esq

My dear Sir

I have no doubt you will see the enclosed paper: but perhaps you will pardon my calling your attention to it by sending it, insomuch as I shall shortly be publishing in connexion with it but not through the same Society some papers which more widely apply the method of heat testing of the germs of the septic organisms which is explained in the enclosed paper; and I shall do myself the pleasure of forwarding them to you.1

I have now in hand a long series of investigations on these putrifactive organisms which deal with the effects of altered environment when the alterations are steadily and slowly made: and the results hitherto palpably demonstrate your great doctrine. With such enormous numbers as are capable of being studied at once, in all stages of their existence, and the comparatively short periods of life-cycle opportunities for the observation of variation and survival are so abundant that the demonstration is comparatively easy. I have hitherto published nothing on this special branch of my researches, partly because they are not as complete as I wish them to be, and partly because I find it so difficult to constantly observe and write at the same time, in a busy life. But I referred in my recent R. Inst. Lectures to one branch2—viz the effect of constantly and carefully added increments of heat on the adult forms. and in my first series of experiments extending over three years I was able to raise the temperature from 45° F. to 137° F. with the adult organism living flourishing and multiplying at the last named temperature.3 Yet if the infusion containing them be suddenly raised from 45° F to 85° F they are in the course of 30 or 40 hours almost wholly destroyed. A painful illustration of this has just happened: my colleague in some of my work—Dr. Drysdale—and I are at work upon a special form just now, and although before these few days of hot weather set in we had it abundantly in a maceration; yet we had it in a covered (small) shed exposed to the sun where the temperature reached (without our thinking of it) about 95° to 100° F and now (after three days) there is not a trace of it left. This of course does not apply to Bacterium tenus and many forms of Vibrio &c.4 But it is a vexatious “control” of my experiments—

With much respect | Believe me | Truly yours | W. H. Dallinger

1
Dallinger sent his paper ‘On the life history of a minute septic organism: with an account of experiments made to determine its thermal death-point’ from the Proceedings of the Royal Society of London (Dallinger 1878). This paper is not in the Darwin Pamphlet Collection–CUL; there are no later papers by Dallinger in the collection either.
2
Dallinger had given a lecture to the Royal Institution of Great Britain on 4 May 1877, entitled ‘Recent researches into the origin and development of minute and lowly life-forms; with a glance at the bearing of these on the origin of bacteria’ (Dallinger 1877).
3
In the Royal Microscopical Society’s Monthly Microscopical Journal, Dallinger had published a series of papers with John James Drysdale challenging the theory that life could be spontaneously generated (Dallinger and Drysdale 1873, 1874, and 1875). The second and third papers are in Darwin Pamphlet Collection–CUL, marked with the authors’ compliments; CD had sent Ernst Haeckel the first in the series (see Correspondence vol. 21, letter to Ernst Haeckel, 25 September 1873). See also Correspondence vol. 24, letter to W. H. Dallinger, [after 10 January 1876].
4
Tenus: the bacterium Clostridium tetani, which causes tetanus. Vibrio is a genus of gram-negative bacteria, characterised by their comma shape, and including V. cholerae, which causes cholera.

Please cite as “DCP-LETT-11576,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-11576