The lacticiferous or milk bearing plants are nearly all of them connected by very important ties with man and civilization. The phenomena themselves are well worthy of study, and their association with humanity replete with interest. These plants are by no means restricted to one genus or family, nor are their properties of the same character. The one circumstance of their secreting a white juice resembling milk in appearance is almost all they have in common. In the poppy it becomes _opium_, in the lettuce _lactucarium_. It constitutes refreshing beverages, obtained in large quantities, in the sunny climes of Asia, from the cow-tree of South America, the kiriaghuma and hya-hya of British Guiana, the _Euphorbia balsamifera_ of the Canary Islands, the juice of which as a sweet milk, or evaporated to a jelly, is taken as a great delicacy, and the Banyan tree, all of which, to a certain extent, supply the place of the cow, in places and conditions wherein cows are not to be found. Similar juices are collected in the form of India rubber or caoutchouc, a substance so invaluable in the arts of life. They exude from figs, euphorbiæ, and cacti, in the East Indies, South America, and Africa, from all of which places a large quantity of the consolidated juice is exported to the markets of Europe and North America. The greater quantity of these lactescent juices are elaborated in the Tropics. Gutta percha and allied substances are similarly produced, and indeed, numerous plants are possessed of this kind of secretion, which have not yet been made available for economical purposes, but which may become equally well known, and useful, to succeeding generations. Narcotic properties do not appear to be so common in these juices as the irritant or acrid, which abound in some euphorbiaceous plants, and the inert, and when coagulated and dry, elastic properties found in the siphonias, figs, and sapotaceous plants. In St. Domingo, a species of _Muracuja_ is believed to possess qualities very similar to opium, from which, and from an allied plant, Dr. Hamilton believes, that the concentrated sap, collected at a proper time, strained, evaporated, and properly prepared, would prove an excellent substitute for the expensive opium, at a cheaper rate. The species indigenous to Jamaica, is known as bull-hoof or Dutchman’s laudanum. At a time when opium was scarce, from some accidental cause, in the island of Jamaica, a Dutch surgeon found in this plant a successful substitute. The plant is common in Jamaica and some other of the West Indian islands. It is an elegant climber, bearing bright scarlet blossoms, somewhat resembling a passion flower. Browne says, that the flowers are principally employed, and when infused, or mixed in a state of powder with wine or spirits, are regarded as a safe and effectual narcotic.