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Darwin Correspondence Project

To J. S. Burdon Sanderson   15 November [1873]1

Down, | Beckenham, Kent.

My dear Dr Sanderson

I have just seen Prof Frankland, and he says that he will send to you in about a week’s time some proprionic and butyric acid, as well as some valeric acid, so as to complete the series; for he thinks that it might have been valeric acid instead of butyric mixed with acetic, which was in drosera;2 and if you will try these acids for artificial digestion I shall be very much obliged. On my return home I will send the globulin and hæmaglobin

Yours very sincerely | Ch. Darwin

Nov 15th. | 2 Bryanston St | Portman Square | (Until early Tuesday morning)3


The year is established by the address. CD stayed in Bryanston Street, London, his daughter Henrietta Emma Litchfield’s house, on 15 November only in 1873.
These acids are naturally occurring carboxylic acids. CD mistakenly wrote ‘valeric’ instead of ‘valerianic’ acid. Burdon Sanderson’s experiments with these acids are described in Insectivorous plants, pp. 89–91.
CD returned to Down on 18 November 1873 (‘Journal’ (Appendix II)).


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


Frankland is sending JSBS organic acids for him to try artificial digestion. CD will send globulin and haemoglobin.

Please cite as

Darwin Correspondence Project, “Letter no. 9143,” accessed on 27 March 2023,

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