The _alkaloids_ found in mushrooms are: _Muscaridine_ (an oxyneurine), which possesses considerable toxicity, and of which 0.00005 Gm. suffices to kill a frog; _neurine_ (trimethylethylammonium hydroxide); _choline_ (trimethyloxyethylammonium hydroxide); _mycetomuscarine_; _anhydromuscarine_ (an oxyneurine); and a whole series of various betaines. =Symptomology.=--It is quite natural to divide this symptomology into three different periods; that of incubation, that of manifestation of symptoms, and that of termination. The duration of the first period, that of incubation, is exceedingly variable; it very rarely lasts more than forty-eight hours, and becomes general only a few hours after absorption. Certain conditions influence the duration; firstly the quantity of mushrooms ingested, then the manner in which they were prepared; and, to some extent, the nature of the organism, whether child or adult, healthy or in poor health. When it is a question of the more particularly alkaloid-containing mushrooms, especially when the poisoning is due to muscarine, the toxic symptoms generally develop rapidly, the first symptoms appearing about one hour after the ingestion of the mushrooms. On the other hand, if the poisoning is due to one of the albuminoid group, and particularly in the case of phallin, the period of incubation is longer, and may last ten, twenty, thirty, or even forty-eight hours and more. The symptoms begin with dizziness and an indefinable sensation of being ill. The second period is characterized chiefly by digestive and by nervous derangements. The digestive derangements are evidenced by very violent and painful vomiting, and diarrheas of choleraic or dysenteric character. The nervous derangements vary according to whether they are developed by an alkaloid, which causes delirium with hallucination, or by albuminoids, which cause depression, ataxo-adynamia, and stupor, these being particularly characteristic of the action of the toxic albuminoids. As for the period of termination, it results either in death or a cure. If the poisoning is due to phallin, death appears to be an almost inevitable consequence, as it occurs in 80 per cent. or more of the cases. The poisoning by the alkaloids is less dangerous, and the cure, when it does occur, is very rapid, almost immediate, in fact, while in the case of the toxic albuminoids the cure is very slow, and attended by relapses. One characteristic of these toxalbumins is that they are apt to develop specific antitoxalbumins. This fact has been verified not only in the case of abrin, ricin, robin, and their analogues, but also in that of the vegetable and animal diastases possessing toxic properties even in the slightest degree only. These antibodies generally exhibit their action _in vitro_. Thus antiricin exerts its antiagglutinative action on the erythrocytes _in vitro_ in a saline medium in which the erythrocytes cannot live.