By the action of methyl iodide (CH_{3}I), pyridinium methyl iodide is formed, which is transformed on heating into α-methyl-pyridine hydriodide. The free base, when treated with acetaldehyde (p. 271), yielded a compound known as α-allyl-pyridine, which, in turn, was made to combine with nascent hydrogen. The resulting compound (isoconiine) becomes coniine on heating to 300° C. or boiling with solid potash. The chemical history is shown graphically below:-- CH CH CH CH // \\ // \\ // \\ // \\ HC CH HC CH HC CH H{2}C CH{2} | | | | | | | | HC CH HC CCH{3} HC CC{3}H{5} H{2}C CHC{3}H{7} \\ // \\ // \\ // \\ // N N N NH Pyridine. α-Methyl-pyridine. α-Allyl-pyridine. Coniine. Pyridine, it may be mentioned, can be built up from its elements. This coniine triumph of synthetic chemistry has been followed by many others of a similar character, and now all the alkaloids mentioned above in connection with pyridine have been produced artificially. Piperine was synthesised by Ladenburg and Scholtz in 1894; atropine together with other solanaceous alkaloids, and cocaine[4] by Willstätter in 1901–2; and nicotine by Pictet in 1903. The structure of these alkaloids is considerably more complicated than that of coniine; atropine, for example, is represented by the formula H H_{2} H_{2}C----C----C CH_{2}OH | / \ | | N--CH_{3} CH--O--CO--CH | \ / | H_{2}C----C----C C_{6}H_{5} H H_{2} The molecule of quinoline contains a benzene and a pyridine nucleus condensed thus:-- HC CH \ C / // \ / \\ HC || CH HC || CH \\ / \ // \\/ C \// HC N Among the alkaloids of the quinoline group may be mentioned those of cinchona bark and nux vomica. The constitution of these alkaloids is very complex, and in most cases but little understood. As an example of the cinchona group quinine may be taken. Its structure is probably