Similar specializations are of frequent occurrence in the history even of scientific nomenclature. "It is by no means uncommon," says Dr. Paris, in his _Pharmacologia_,[16] "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 _Αρσενίκον_, 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 most usually occurred. So the term _Verbena_ (quasi _Herbena_) 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; 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 (_ὀπὸς_, _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 _ἐλαύνω_, _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, 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 _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