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Darwin Correspondence Project

From S. W. Moore   3 October 1873

113 Brixton Road | S.W.

3. 10. 73

Dear Sir

I thank you very much for your kind letter, & offer of your works,1 I have free access to the British Museum Library & have taken great interest in the perusal of your works generally the last of them the “Expression of Emotions” has afforded me some very useful & instructive reading & it would give me great pleasure to hold one from your hands.

I have been collecting facts for some time, purposely to explain & illustrate a matter wrapped in great mystery & that is the cause of marks, nævi, malformations etc received in utero & I think many of your remarks in the above lead to suggestive thoughts on this matter.2

I am sorry I did not take sufficient care in the sending of the syntonine, but about 1 dram of pepsin to 1 quart of water & 12 an ounce of your dilute acid would meet the case, that is 3 grains of pepsine to 2 oz water with .2% hydrochloric acid, pepsine of shops contains variable quantities of starch so that double that quantity might be used.3

I do not entirely agree with Watts in this case   a certain amount of vegetable matter is soluble in water but hardly of legumen because in the residue but a small proportion Nitrogen is to be found; when peas are boiled they lose but little of the 25.% legumen they contain because it is this body that gives them their special nutrient properties, it seems to me to be more the starchy matter which dissolves, in conjunction with some of the chlorophyll a matter not considered so fully in the days of Gerhardt; if however the seeds were germinating then a soluble form of albumen does exist & may be dissolved in water4

In a few days you may expect the Chlorophyll5 & I trust you will not consider you are troubling me if you should want further assistance

I remain | Dear Sir | Yours very truly | S. W. Moore.

Ch Darwin Esqe F.R.S.

CD annotations

1.1 I thank … matter. 2.4] crossed pencil
2.1 I have … matter. 2.4] marked with cross in margin blue crayon
3.3 .2] ‘12 minims of’ added pencil
3.3 pepsine of shops … be used. 3.5] ‘Use Dr. Moores pro tem’ added pencil
4.1 I do not … found; 4.3] ‘Legumes’ added pencil
5.1 In … assistance 5.2] crossed pencil
Top of letter: ‘Nitrogenous Fluids’ blue crayon; ‘Cabbage & Peas & Grass & Tea’6 red crayon


CD’s letter to Moore has not been found, but see the letter from S. W. Moore, [1 October 1873].
See, for example, Variation 2: 7–24.
In Insectivorous plants, p. 102, CD credited Moore with preparing syntonin (extracted from muscle) for him; CD wanted to test its effect on the insectivorous plant Drosera (the sundew), in order to discover which compounds in its food it reacted to. Syntonin could be prepared by treating fibrin with pepsin and dilute hydrochloric acid (see Klein et al. 1873, 1: 484).
In Insectivorous plants, p. 82, CD described how he had boiled peas, allowed the decoction to settle, and put drops of the superincumbent liquid on the leaves of Drosera. He also cited Watts 1872–4, 3: 568, for Charles Gerhardt’s remark in Gerhardt 1853–6, 4: 493, that legumin was present in peas in combination with an alkali, forming an incoagulable solution, which, in CD’s words, would ‘mingle’ with boiling water. Moore seems to doubt that CD’s method would have succeeded in extracting legumin from the peas.
CD credited Moore with sending him chlorophyll, and described his experiments with placing particles of it on the leaves of Drosera, in Insectivorous plants, pp. 125–6.
CD experimented with placing solutions of these items on the leaves of Drosera (see Insectivorous plants, pp. 78, 82, 83, 84).


Gerhardt, Charles. 1853–6. Traité de chimie organique. 4 vols. Paris, Leipzig: Firmin Didot frères.

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

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.

Watts, Henry. 1872–4. A dictionary of chemistry and the allied branches of other sciences. 2d edition. 5 vols. London: Longman, Green, & Co.


Sends formula for pure pepsin for experiments on digestion of Drosera, and information on legumin. Will send chlorophyll soon.

Letter details

Letter no.
Samuel William Moore
Charles Robert Darwin
Sent from
London, Brixton Rd, 113
Source of text
DAR 58.1: 41–2
Physical description
3pp †

Please cite as

Darwin Correspondence Project, “Letter no. 9086,” accessed on 15 June 2021,

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