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Darwin Correspondence Project

To T. L. Brunton   25 May [1874]1

Down, | Beckenham, Kent.

May 25th

My dear Sir

You are very kind, & I am sure have not the least cause to apologise for delay in writing.2

The globules in the residue from the milk certainly had exactly the same appearance before any balsam was near the slide. Hence I will assume that the globules were oil. I am not surprised at the presence of bacteria or any other organisms, as the milk was sometimes digesting on the open leaves.—

I am particularly obliged for the information about the strength of the acids & albumen: I doubted at the time whether the cause might not be that the leaves were injured by 1100 of acid, as the glands were a little discoloured; & I have now no doubt that this is the explanation.—3

I shall be glad to hear about the pepsin: I used some which was called pure & made for me by Dr. Moore of Brixton Rd. & Drosera certainly could dissolve very little of this, though the associated albumen or the pepsin itself excited the leaves.4

With very many thanks | Yours sincerely | Ch. Darwin

I shall be curious to hear about the papaw juice.—5


The year is established by the relationship between this letter and the letter to T. L. Brunton, 11 May 1874.
Brunton’s reply to CD’s letter of 11 May 1874 has not been found. CD’s questions were about the microscopic appearance of milk, and the digestion of milk by Drosera (sundew).
CD refers to Samuel William Moore; for CD’s and Brunton’s experiments with pepsin, see Insectivorous plants, pp. 123–4.
In his response to CD’s letter of 11 May 1874, Brunton had evidently mentioned the digestive properties of the juice of the papaw fruit (Carica papaya). Brunton described the digestive action of the ferment derived from the fruit (papain) in Brunton 1885, pp. 777–8.


Brunton, Thomas Lauder. 1885. A text-book of pharmacology, therapeutics and materia medica; adapted to the United States pharmacopœia. London: Macmillan & Co.

Insectivorous plants. By Charles Darwin. London: John Murray. 1875.


CD responds to information about residue of milk digested by Drosera. Is obliged for information on strength of acids and albumen and now has little doubt acid had impaired the leaves. Awaits word on pepsin and papaw juice.

Letter details

Letter no.
Charles Robert Darwin
Thomas Lauder Brunton, 1st baronet
Sent from
Source of text
American Philosophical Society (Mss.B.D25.)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9468,” accessed on 21 September 2021,

Also published in The Correspondence of Charles Darwin, vol. 22