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Darwin Correspondence Project

From J. S. Burdon Sanderson   25 June 1873

49 Queen Anne St.

June 25th. 1873

My dear Sir

It has been a great pleasure to me to receive your letter. I will at once proceed to make some notes on the Paper you have been so kind as to send to me & particularly on the marked passages.1

Ad 3. Sodium salts may be injected into the circulation of mammals in very large doses without effect. Very small doses of potassium salts produce death by suddenly arresting the contractions of the heart.2 This fact I have verified experimentally.

Ad 7. I can give you no explanation of the result obtained with Extract of Belladonna.3 I will write again on this subject

Ad 8. On the matter of Calabar bean I will write to Dr Fraser4

Ad 11 I believe that the citrate of Strychnine wd. be as good a salt as could be used.5

Ad 14 The negative result in the case of Curare is very interesting. It may I think be compared with the equally negative result obtained with Colchicine. Both are muscular poisons. I will send you some veratrine the alkaloid of Cevadilla which acts on muscle in the same way as Colchicine and does not act on nerve    If it is found that veratrine does not act on the Sundew it would I think be of interest.6

Another agent (very accessible) which acts on nerve & is without action on muscle is glycerine. If a very weak solution of glycerine in water produces inflection, this wd. indicate that the excitability of Drosera is allied to that of nerve rather than to that of muscle.7

No doubt the most important fact of all is the one recorded in Par. 2. The action cannot be due to the presence of nitrogen—nor to the presence of nitrogenous compds. for these exist in vegetable liquids—in the very tissues and juices of the leaf itself— It must be dependent on the action of a ferment. To determine this it would be interesting to observe 1st. whether carbolic acid acts on the Drosera in ferment-destroying dose (say in 12 per cent solution) & secondly whether the same agent when added to an animal liquid (e.g. Saliva) inhibits its action.8

The best expt. for this purpose would be first to give the leaf some carbolic acid (half per cent solution) and then follow it with the Saliva.

If it is not too late and I could do so without disturbing either you or your Droseras I should like extremely to witness some of the facts9

Believe me my dear Sir | very truly yours | J S B Sanderson

CD annotations

1.1 It has … passages. 1.3] crossed ink
2.1 Ad … used 5.1] crossed pencil
6.2 Both … poisons. 6.3] scored red crayon
6.3 which acts … Colchicine 6.4] scored red crayon
7.2 If … muscle. 7.4] scored red crayon
8.4 To determine … action. 8.7] crossed pencil
10.1 If … facts 10.2] crossed red crayon
Top of letter: ‘Glycerine | Effects of salts of Sodium & Potassium [‘Sodium’ and ‘Potassium’ underl red crayon] | Veratrin [above del ‘Veratrin’] Curare Colchichin [below del ‘Colchin’]’ pencil next to red crayon pointing hand; ‘Carbolic acid Try | Poisonsred crayon


See letter to J. S. Burdon Sanderson, 24 June 1873; CD’s enclosed paper has not been found.
CD reported the effects of salts of sodium and potassium on Drosera (sundew) in Insectivorous plants, pp. 174–81; he cited Burdon Sanderson on the effects of these substances on animals (ibid., p. 187).
In Insectivorous plants, p. 84, CD reported that extract of Atropa belladonna (deadly nightshade) caused some inflection of the leaves of Drosera.
Calabar bean is the seed of Physostigma venenosum, native to tropical Africa. Thomas Richard Fraser had published on the physiological effects of the bean (Fraser 1867).
Citrate of strychnine is an acid salt of the alkaloid strychnine. On CD’s results with the compound, see Insectivorous plants, pp. 200–1.
CD described his results with colchicine, curare, and veratrine in Insectivorous plants, pp. 204–5. These alkaloids were known to have different effects on muscle tissue. Veratrine, derived from the seeds of sabadilla (Schoenocaulon officinale), increases nerve excitability and is now classed as a neurotoxin.
CD found little effect on Drosera with a dilute solution of glycerine; however, pure glycerine caused marked inflection and was poisonous (Insectivorous plants, pp. 212–13).
CD determined that Drosera secreted digestive acid in conjunction with a ‘ferment’ to break down organic matter (see Insectivorous plants, pp. 85ff. The ferment would later be known as a digestive enzyme.
Sanderson visited Down House on 4 July 1873 (Emma Darwin’s diary (DAR 242)).


Fraser, Thomas Richard. 1867. On the physiological action of the Calabar bean. Transactions of the Royal Society of Edinburgh 24: 715–88.

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


Informs CD of the effects of certain salts and other chemicals on animals.

Comments on CD’s results with Drosera. Suggests some experiments.

Letter details

Letter no.
John Scott Burdon Sanderson, baronet
Charles Robert Darwin
Sent from
London, Queen Anne St, 49
Source of text
DAR 58.1: 116–19
Physical description
8pp †

Please cite as

Darwin Correspondence Project, “Letter no. 8949,” accessed on 24 September 2021,

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