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—D^r. 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