The lowest animal group in which these secretions begin to be clearly differentiated is that of the _Coelenterates_. A.--COELENTERATES. It has been shown by Charles Richet[108] that the tentacles of sea-anemones (_Anemone scultata_) contain a toxic substance which has the carious property of causing intense itching, pruritus, and even urticaria. This poison is perfectly soluble in alcohol, and can be prepared in the following manner:-- 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.