The tentacles are cut off close to the body of the animal, and immersed for a few days in an equal weight of alcohol at 95° C. The red liquid that results is decanted, and then filtered. The insoluble material is compressed, and yields large quantities of fluid, which is filtered and mixed with the previous liquid.
The whole is then evaporated in vacuo until there remains a thick oily liquid, which forms a red deposit. Filtration through paper is again employed, in order to separate this colouring matter, and to the filtered liquid is added an equal amount of alcohol at 95° C. By this means there is precipitated a blackish, gummy matter, insoluble in alcohol. The remaining liquid is decanted and once more evaporated until it is reduced to a smaller volume than before. It is again treated with twice its volume of absolute alcohol, when it precipitates, in addition to salts and gummy matter, a white flocculent substance, which is crude thalassin. This can be purified by redissolving it in alcohol at a temperature of 98° C. On cooling it separates from the fluid in the form of crystals, which are placed on a filter and can then be redissolved in a small quantity of water. Absolute alcohol, added to this solution, precipitates the thalassin in the shape of very pure crystals, which contain 10 per cent. of azote, and melt at 200° C.
This substance, in aqueous solutions, rapidly deteriorates owing to ammoniacal fermentation. When injected intravenously into dogs it produces pruritus, sneezing, and erythema, with intense congestion of the mucous membranes; 1 decigramme per kilogramme is a dose sufficient to produce these symptoms. It is not very toxic, since 1 centigramme is not lethal.
One kilogramme of anemones is capable of furnishing about 3 grammes of pure crystallised poison.
In addition to thalassin, Richet succeeded in isolating from the tentacles of the same sea-anemones another poison insoluble in alcohol at 50° C., and richer in azote (14 per cent.), to which he has given the name congestin. This is not destroyed by heating to 107° C. It is prepared by precipitating, by four times its volume of alcohol, a solution of anemone-tentacles in 5 per cent. fluoride of sodium. The solid matter, after being precipitated and dried, is redissolved in six times its volume of water, and then filtered. On adding to the filtered and fluorescent liquid its volume of alcohol at 90° C., the congestin is precipitated. It is purified by redissolving it in water, and freeing it by dialysis from the fluoride of sodium that it has retained. In this way there is obtained, after evaporation, a product sufficiently toxic to kill dogs in twenty-four hours in a dose of 2 milligrammes per kilogramme.
Congestin exerts a sensitising or anaphylactic effect upon animals as regards thalassin, and is lethal in a dose of about 5 milligrammes per kilogramme of animal, and sometimes even in a dose of 7 decimilligrammes. It is therefore a very active poison.
Dogs, on the other hand, into which is injected first thalassin, and then, some time afterwards, congestin, are perfectly resistant to inoculation by the latter. Thalassin is therefore antitoxic or antagonistic to congestin.
The latter, on the contrary, if injected first of all in non-lethal doses, renders animals so sensitive to inoculation with thalassin, that from 4 to 5 milligrammes are sufficient to cause death.
The tentacles of these anemones therefore contain two toxic substances antagonistic to each other, which can easily be separated, since one (thalassin) is soluble in concentrated alcohol, while the other is completely insoluble in this reagent.
These poisons are not only extremely interesting from a physiological point of view, but also possess a practical interest, since it is at the present time almost a matter of certainty that they are the cause of a malady which specially affects sponge-divers in the Mediterranean.