To Simpson, there is no doubt, belongs the merit of having made anæsthesia triumph over all the opposition, which was at first, actively, offered to its use. For this he well deserved the rewards which fell upon him in the evening of his life. Among those who aided in the establishment of the use of anæsthetics, mention must be made of the work of John Snow, who by his researches placed the practice on a scientific basis. The advent of chloroform gave an impetus to other investigators in the field of anæsthesia, and during the last fifty years many other bodies have been introduced and tried with more or less success for the same purpose. Methyl chloride, which was discovered by Dumas and Peligot, was introduced by Deboe in 1887, who used it extensively in local affections. In 1867, Sir B. W. Richardson introduced methyl bichloride or methylene [methylene dichloride]. He formed a very high estimate of its properties as a good general anæsthetic, and said he preferred it for many reasons to chloroform, as he found that the anæsthetic sleep was produced more quickly and was more prolonged. Sir T. Spencer Wells also advocated its use, and stated, in 1872, that it had fewer drawbacks than any then known anæsthetic. Tetra-chloride of methyn [carbon tetrachloride], which much resembles chloroform, was discovered by Regnault in 1839, and its anæsthetic properties were first made known by Sansom and Harley in 1864. Simpson was of the opinion that it had a more depressing effect upon the heart than chloroform, and was more dangerous generally as an anæsthetic. Nunneley, of Leeds, also contributed work of value in this department of research, and introduced ethyl bromide and chloride of carbon. He dispelled the idea, long prevalent, that anæsthetics could be found only in a limited class of chemical compounds. Among other substances which have been introduced during the last twenty-five years, but which, owing to one defect or another, have since been practically abandoned, mention should be made of butylic hydride [butane], ethylene, amylene, ethyl nitrate, aldehyde (introduced by Poggiale), carbon bisulphide, ethidene dichloride [ethylene dichloride] (discovered by Regnault and first used as an anæsthetic by Snow), and ethyl bromide, first prepared by Serullus in 1827. LOCAL ANÆSTHETICS Local anæsthesia, already alluded to as probably the earliest form of numbing sensibility to pain, was practised in antient times by the inunction of various narcotics, but after the seventeenth century the practice seems to have almost entirely gone out of use. The latter end of the nineteenth century, however, marks a new era in this department. On September 15th, 1884, considerable interest was aroused by a communication made at the Ophthalmological Congress at Heidelberg, by Karl Koller, of Vienna, in which he demonstrated the effects of cocaine as a local anæsthetic. [Sidenote: The discovery of Cocaine]