American Worm seed oil, known as Chenopodium oil, is colourless or yellowish, when freshly distilled, becoming deeper yellow and even brownish by use. It has a peculiar, penetrating, somewhat camphoraceous odour (the peculiar odour of the plant), and a pungent, bitter taste. Its chief constituent is Ascaridole, to the high percentage of 60 to 70 per cent, an unstable substance, allied to cineal, readily decomposed on heating, with the production of a hydrocarbon. It also contains p-cymene, a-perpinene, probably dihydro-p-cymene and possibly sylvestrene. Betzine and choline have also been reported. This is the reason it has supassed all the previous remedies tried to control roundworms.