Most strangely, this family also, as well as the following and last, exhibits the peculiar phenomenon which was described in the first-named, the Euphorbiaceæ, namely, that the milk-sap is in some species rich in India-rubber, in others it is tempered into a clear, agreeably smelling and wholesome milk, while in certain others, on the contrary, this fluid grows, step by step, through successively increasing quantity of noxious matter to a most dreadful poison. In the forests of British Guiana grows a tree which the natives call Hya-Hya (Tabernæmontana utilis). Its bark and pith are so rich in milk that an only moderate-sized stem, which Arnott and his companions felled on the bank of a large forest brook, in the course of an hour colored the water quite white and milky. This milk is perfectly harmless, of a pleasant flavor, and is taken by the savages as a refreshing drink. Still more pleasant must be the taste of the milk of the Ceylon cow-tree, the Kiriaghuma (Gymneura lactiferum), which, according to Burmann’s narrative, the Cingalese use exactly as we do milk. Dreadful, on the contrary, is the action of the terrible wourali poison, which the inhabitants of the banks of the Orinoco concoct with mystic conjurations, the chief ingredients of which are furnished by the juice of a plant belonging here (Echites suberecta) and the bark of another, likewise an Apocynaceous tree, Strychnos guinanensis and Strychnos toxifera. The North Americans also use an Apocynaceous plant (Gonolobium macrophyllum) to poison their arrows; and Mungo Park related the like of the Mandingoes of the Niger (according to him it is a species of Echites). Many allied plants are among the most active poisons (Cerbera Thevetia and Cerbera Ahovai), and the seeds of this group, in particular, are almost more remarkable for their deadliness than those of the foregoing, for two of the most violent vegetable poisons, strychnine and brucine, occur in them. Some of our most active medicinal substances are especially known on this account; for instance, the St. Ignatius’s beans (Ignatia amara from Manila), and the Nux vomica (Strychnos nux Vomica), distributed throughout the tropics.