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It has been already stated that we are to a great degree ignorant of the Simples used by the ancient Physicians; we are often quite unable to determine what the plants are of which Dioscorides treats. It does not appear that out of the 700 plants of which his Materia Medica consists, that more than 400 are correctly ascertained; and yet no labour has been spared to clear the subject of its difficulties; Cullen even laments that so much pains should have been bestowed upon so barren an occasion.^[76] The early history of botany presents us with such a chaos of nomenclature, that it must have been impossible for the herbarist and physician to have communicated their mutual lights; every one was occupied with disputes upon words and names, and every useful inquiry was suspended, from an inability to decide what plant each author intended; thus, for instance, the Herba Britannica of Dioscorides and Pliny, so celebrated for the cure of the soldiers of Julius Cæsar on the Rhine, of a disease called ‘Scelotyrbe’, and supposed to resemble our sea scurvy, remains quite unknown, notwithstanding the labours of our most intelligent commentators.^[77] It seems also very doubtful whether the plant which we denominate Hemlock was the poison usually administered at the Athenian executions,^[78] and which deprived Socrates and Phocion of life. Pliny informs us that the word Cicuta, amongst the ancients, was not indicative of any particular species of plant, but of vegetable poisons in general; this is a circumstance to which I am particularly anxious to fix your attention; it is by no means uncommon to find a word which is used to express general characters, subsequently become the name of a specific substance in which such characters are predominant; and we shall find that some important anomalies in nomenclature may be thus explained. The term ‘Αρσενικον,’ from which the word Arsenic is derived, was an ancient epithet, applied to those natural substances which possessed strong and acrimonious properties, and as the poisonous quality of arsenic was found to be remarkably powerful, the term was especially applied to Orpiment, the form in which this metal more usually occurred. So the term Verbena (quasi Hebena) originally denoted all those herbs that were held sacred on account of their being employed in the rites of sacrifice, as we learn from the poets;^[79] but as one herb was usually adopted upon these occasions, the word Verbena came to denote that particular herb only, and it is transmitted to us to this day under the same title, viz. Verbena, or Vervain, and indeed until lately it enjoyed the medical reputation which its sacred origin conferred upon it, for it was worn suspended around the neck as an amulet. Vitriol, in the original application of the word, denoted any crystalline body with a certain degree of transparency (Vitrum); it is hardly necessary to observe that the term is now appropriated to a particular species: in the same manner, Bark, which is a general term, is applied to express one genus, and by way of eminence, it has the article, The, prefixed, as The Bark: the same observation will apply to the word Opium, which in its primitive sense signifies any juice (οπος Succus) while it now only denotes one species, viz. that of the Poppy. So again, Elaterium was used by Hippocrates, to signify various internal applications, especially purgatives of a violent and drastic nature (from the word ‘Ελαυνω,’ agito, moveo, stimulo), but by succeeding authors it was exclusively applied to denote the active matter which subsides from the juice of the wild cucumber. The word Fecula, again, originally meant to imply any substance which was derived by spontaneous subsidence from a liquid, (from fæx, the grounds or settlement of any liquor); afterwards it was applied to Starch, which is deposited in this manner by agitating the flour of wheat in water; and lastly, it has been applied to a peculiar vegetable principle, which like starch^[80] is insoluble in cold, but completely soluble in boiling water, with which it forms a gelatinous solution; this indefinite meaning of the word fecula has created numerous mistakes in pharmaceutic chemistry; Elaterium, for instance, is said to be a fecula, and in the original sense of the word it is properly so called, inasmuch as it is procured from a vegetable juice by spontaneous subsidence, but in the limited and modern acceptation of the term, it conveys an erroneous idea; for instead of the active principle of the juice residing in fecula, it is a peculiar proximate principle, sui generis, to which I have ventured to bestow the name of Elatin. For the same reason, much doubt and obscurity involve the meaning of the word Extract, because it is applied generally to any substance obtained by the evaporation of a vegetable solution, and specifically to a peculiar proximate principle, possessed of certain characters, by which it is distinguished from every other elementary body—See Extracta. On the other hand, we find that many words which were originally only used to denote particular substances, have, at length, become subservient to the expression of General Characters; thus the term Alkali, in its originally sense, signified that particular residuum which was alone obtained by lixiviating the ashes of the plant named Kali, but the word is now so generalized that it denotes any body possessed of a certain number of definite properties.