their voracious enemies.  One of the essential oils, that of turpentine, is recommended, by M. de Thosse, for the purpose of destroying insects which infect both vegetables and animals.  Having observed that the trees were attacked by multitudes of small insects of different colours (pucins ou pucerons), which injured their young branches, he destroyed them all intirely in the following manner:  he put into a bowl a few handfuls of earth, on which he poured a small quantity of oil of turpentine; he then beat the whole together with a spatula, pouring on it water till it became of the consistence of soup; with this mixture he moistened the ends of the branches, and both the insects and their eggs were destroyed, and other insects kept aloof by the scent of the turpentine.  He adds, that he destroyed the fleas of his puppies by once bathing them in warm water impregnated with oil of turpentine.  Mem. d’Agriculture, An. 1787, Trimest.  Printemp. p. 109.  I sprinkled some oil of turpentine, by means of a brush, on some branches of a nectarine-tree, which was covered with the aphis; but it killed both the insect and the branches:  a solution of arsenic much diluted did the same.  The shops of medicine are supplied with resins, balsams, and essential oils; and the tar and pitch, for mechanical purposes, arc produced from these vegetable secretions.]

185 In sulphurous eddies round the weird dame
        Plays the light gas, or kindles into flame. 
        If rests the traveller his weary head,
        Grim MANCINELLA haunts the mossy bed,
        Brews her black hebenon, and, stealing near,
190 Pours the curst venom in his tortured ear.—­
        Wide o’er the mad’ning throng URTICA flings
        Her barbed shafts, and darts her poison’d stings.

[Mancinella, I. 188.  Hyppomane.  With the milky juice of this tree the Indians poison their arrows; the dew-drops, which fall from it, are so caustic as to blister the skin, and produce dangerous ulcers; whence many have found their death by sleeping under its shade.  Variety of noxious plants abound in all countries; in our own the deadly nightshade, henbane, hounds-tongue, and many others, are seen in almost every high road untouched by animals.  Some have asked, what is the use of such abundance of poisons?  The nauseous or pungent juices of some vegetables, like the thorns of others, are given them for their defence from the depredations of animals; hence the thorny plants are in general wholesome and agreeable food to graminivorous animals.  See note on Ilex.  The flowers or petals of plants are perhaps in general more acrid than their leaves; hence they are much seldomer eaten by insects.  This seems to have been the use of the essential oil in the vegetable economy, as observed above in the notes on Dictamnus and on Ilex.  The fragrance of plants is thus a part of their defence.  These pungent or nauseous juices of vegetables have supplied the science of medicine with its principal materials, such as purge, vomit, intoxicate, &c.]