Veronal.
Attempts have been made to connect the physiological working of local anæsthetics with particular constitutional groupings, as, for example, in cocaïne; and these have led to the introduction of such substances as the orthoforms, nirvanine, stovaïne, alyhine, novocaïne, and adrenaline into medicine. Adrenaline, used in conjunction with cocaïne, has proved itself a most valuable agent in producing what is called lumbal anæsthesia, whereby large sections of the lower half of the body may be rendered completely insensitive to pain.
The study of the putrefactive changes of albuminous substances of animal origin, induced by the activity of micro-organisms, has revealed the existence of a number of basic nitrogenous compounds, some of which are highly poisonous. These were classed by Selmi under the generic name of ptomaines (πτῶμα, a corpse). Brieger found that the typhoid bacillus yielded a poisonous substance—typhotoxine, and that the bacillus of tetanus forms a highly toxic basic body, tetanine. All the ptomaines, however, are not poisonous. Some of them, like choline (χυλὴ, bile)—originally discovered by Strecker in bile, in the brain, in yolk of egg, and now found to be among the products of the putrefaction of meat and fish—have been known for some time past. Choline was first synthetically prepared by Wurtz. Neurine (νεὺρον, nerve), a derivative of brain substance, is related to choline, and is readily transformed into it, but differs from it in being very poisonous. It has been synthesised by Hofmann and by Baeyer. Another of the so-called corpse-alkaloids—cadaverine—has been synthetically formed by Ladenburg. Schmiedeberg and Kopp isolated the poisonous principle of the fungus agaricus muscarius, which they named muscarine. It occurs with choline, from which it can be readily obtained, among the products of the putrefaction of flesh, as well as in many fungi.
The synthesis of the alkaloids conine, atropine, cocaïne, piperine, and nicotine has been already referred to[5] as also that of vanillin, the aromatic principle of the dried fermented pods of certain orchids; coumarin, the odoriferous principle of woodruff and of the tonka bean; of salicylic acid, oil of wintergreen, oil of mustard, bitter-almond oil, and camphor. Acetic, succinic, tartaric, and citric acids have also been artificially obtained, and may, indeed, be built up from their elements.
[5] P. 133.
No synthesis of recent years created more widespread interest than that of alizarin, first effected by Graebe and Liebermann in 1868. Its successful commercial manufacture by Sir William Perkin in this country and by Caro in Germany created nothing less than a revolution in one of our leading industries, and completely destroyed a staple trade of France, Holland, Italy, and Turkey. To procure alizarin, anthraquinone is treated with sulphuric acid, and the product is fused with alkali and potassium chlorate.
The remarkable industrial results attending the synthetical formation of this madder-product naturally led to attempts to procure other important vegetable dye-stuffs artificially, notably indigo. The synthetical production of indigo has been accomplished by the joint labours of many chemists, notably Baeyer, Heumann, and Heymann, and the substance is now prepared on an industrial scale. The starting-point is naphthalene, obtained from coal-tar. This is converted into phthalic acid, which is then transformed into phthalimide. The last-named substance is converted into anthranilic acid, which, on treatment with monochloracetic acid, is changed into phenylglycin-ortho-carbonic acid. On melting this with caustic potash it yields indoxyl acid, which is transformed into indoxyl, and thence into indigo.
Another method is to treat the sodium salt of phenylglycin with sodamide, whereby indoxyl is at once obtained, and this by condensation yields indigo blue:
