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Darwin Correspondence Project

To Edward Frankland   12 July 1873

Down, | Beckenham, Kent.

July 12. 1873

My dear Sir

I am going to beg a great favour of you, if you can by means of any trustworthy assistant aid me. If you cannot, perhaps you can inform me whether there is any professional chemist on whom I cd rely to test a small quantity of fluid, not quantitively, but qualitively. The glands of Drosera secrete a very viscid slightly acid fluid, which dissolves animal matter out of the bodies of insects. I have lately proved this power by giving the leaves little measured cubes of the hardened white of eggs & of gelatine; keeping similar cubes damp on moss, as a standard of comparison.1

Now what I want to know is, what agent, apparently an acid, can dissolve in abt 2 days hardened albumen & gelatine at an ordinary temperature. I suppose that it is not probable that the fluid contains muriatic acid like our gastric juice.2 Several years ago when I was at work at this plant, I consulted Hoffman, who offered to test the fluid, & gave me some pure carbonate of ammonia, to dissolve in distilled water, & then to wash a large number of glands in it.3 Do you think this a good plan? And if so, whether or not you can aid me by getting the fluid tested, will you give me a few grains of pure C. of Ammonia? I know how valuable your time is, & I shd not have thought of troubling you, had I not felt convinced that Drosera is a very remarkable plant under a physiological point of view—

I say this with some confidence as Huxley & Burdon Sanderson have thought it worth while to come here to verify some of my statements.4

My Dear Sir | yours sincerely | Ch. Darwin


CD describes these experiments with albumen and gelatine in Insectivorous plants, pp. 92–8 and 110–12.
Muriatic acid: i.e. hydrochloric acid.
August Wilhelm von Hofmann supplied CD with gelatine and pure sodium carbonate in 1862 (see Correspondence vol. 10, letter from A. W. Hofmann, 27 June 1862, and Insectivorous plants, pp. 111 and 176).
Thomas Henry Huxley visited Down on 27 and 28 June 1873; John Scott Burdon Sanderson visited on 4 July 1873 (letter to J. D. Hooker, 28 June 1873, and Emma Darwin’s diary (DAR 242)).


Seeks the assistance of a professional chemist in securing a qualitative analysis of the fluid secreted by the glands of Drosera which have the power of dissolving animal matter out of the bodies of insects. [See 8979.]

Letter details

Letter no.
Charles Robert Darwin
Edward Frankland
Sent from
Source of text
The John Rylands Library, the University of Manchester
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 8977A,” accessed on 19 March 2018,

Also published in The Correspondence of Charles Darwin, vol. 21