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. A good description of the disease has been given by Dr. Skévos Zervos, of Athens.[109] It is observed exclusively in men who dive quite naked, without a diving-dress. Now, beside the bases of the sponges and sometimes on their surface there live numbers of anemones which secrete a viscid substance, which is extremely virulent, especially in the month of August.