=Choline.=--This alkaloid is of wide occurrence in the animal and vegetable kingdoms. It has been isolated from _Amanita muscaria_, _A. pantherina_, _Boletus luridus_, and _Helvella esculenta_. It is not very toxic, but on uniting with oxygen it passes over to muscarine. According to Kobert the substance formed from choline on the decay of the mushrooms containing it is not muscarine, but a very closely related alkaloid, _neurin_. This transformation of a comparatively harmless alkaloid to an extremely deadly one simply by the partial decay of the plant in which the former is normally found, emphasizes very much the wisdom of rejecting for table use all specimens which are not entirely fresh. This advice applies to all kinds of mushrooms, and to worm-eaten and otherwise injured, as well as decayed ones. Neurin is almost identical in its physiological effects with muscarine, which is described below. =Muscarine.=--This is the most important because the most dangerous alkaloid found in the mushrooms. It is most abundant in _Amanita muscaria_, it is also found in considerable quantity in _Amanita pantherina_, and to a lesser, but still very dangerous extent in _Boletus luridus_ and _Russula emetica_. It is quite probably identical with bulbosine, isolated from _Amanita phalloides_ by Boudier. _Muscarine_ is an extremely violent poison, .003 to .005 of a gram (.06 grain) being a very dangerous dose for a man. Like other constituents of mushrooms, the amount of muscarine present varies very greatly with varying conditions of soil and climate. This, indeed, may account for the fact that _Boletus luridus_ is regarded as an edible mushroom in certain parts of Europe, the environment being such that little or no muscarine is developed. According to Kobert, _Amanita muscaria_ contains, besides choline and muscarine, a third alkaloid, _pilz-atropin_. This alkaloid, like ordinary atropin, neutralizes to a greater or less extent the muscarine. The amount of pilz-atropin present varies, as other constituents of mushrooms vary, with varying conditions of soil, climate, etc., and it may be that in those localities where the _Amanita muscaria_ is used for food the conditions are favorable for a large production of pilz-atropin which neutralizes the muscarine, thus making the plant harmless. Be this as it may, _Amanita muscaria_, so deadly as ordinarily found, is undoubtedly used quite largely as food in parts of France and Russia, and it has been eaten repeatedly in certain localities in this country without harm.