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The value of this classification has been very justly stated to consist in its combining to a certain degree, the advantages of a pathological arrangement with those of one founded on the basis of Natural History; for, while it is strictly pathological, it at the same time distributes the different poisons, with some few and unimportant exceptions, in an order corresponding with that of their natural history. The First two classes, for instance, present us with substances of a mineral origin; the Third and Fourth, with those which are chiefly of a vegetable nature; and the Sixth, with objects principally belonging to the animal kingdom. The importance of acknowledging a division, which has a reference to the organic and inorganic kingdoms of Nature, is considerable in a chemical point of view; for in enumerating the various experiments to be instituted for the detection of poisons, we are thus enabled to bring together a connected series of processes, nearly allied to, intimately connected with, and in some respects mutually dependent upon, each other. At the same time it must be acknowledged, that this classification has many defects and some fallacies. In the first place, it has little or no reference to the enlarged views of the modern physiologist, respecting the “modus operandi” of Poisons; nor indeed is its construction susceptible of such modifications and improvements, as can ever render its degree of perfection progressive with the advancement of science. In the next place, the classes are in many particulars ill defined, and indistinctly, if not erroneously, divided. How questionable, for instance, are the boundaries which separate Corrosive from Acrid poisons? the respective species, even, of each class are, in many cases, less allied to each other, than are the great divisions to which they are subordinate. As an exemplification of this fact we have only to compare the physiological actions of Arsenic and Corrosive Sublimate, both of which are arranged under the class of Corrosive Poisons. The former of these substances undoubtedly occasions death by being absorbed, and thus acting as a vital agent; the latter, by its local action, as a caustic on the textures with which it immediately comes into contact. In the same manner, if we examine the individual actions of the different species composing the class of “Acrid Poisons,” we shall discover the same want of uniformity; thus, the Spurge Flax, and the Iatropa Curcas, act by occasioning a local inflammation, while the Hellebore, being rapidly absorbed, exerts a fatal action on the nervous system, and produces only a very slight inflammation. The class of Narcotic Poisons is certainly more absolute in its definition, and more uniform in its physiological affinities, and therefore less objectionable than the divisions to which we have just alluded; but the propriety of the class “Narcotico-Acrid” is by no means equally unexceptionable; indeed Orfila himself questions it, “because the narcotic or sedative effects only follow the previous excitement.” Some of the poisons of this division also are rapidly absorbed, and act, through the medium of the circulation, on the nervous system, without producing any local inflammation; while others, on the contrary, merely act upon the extremities of the nerves, with which they come in contact, and, without being absorbed, occasion death by a species of sympathetic action.