The general conception of selenium is that it is a comparatively rare element. Few realize that it has been known for over a century and that over twenty selenium minerals, containing from one to sixty-six per cent. of the metal, are considered by the mining corporations as important. Beside being a by-product of sulphuric acid manufacture, it is separated also in the electrolytic refining of copper. The demand for the metal is so small that there are half a dozen concerns in the United States either willing to supply gratis any reasonable quantity for research work, or to sell it at cost. In a special report of the National Research Council on selenium(3), it is estimated that there could be produced annually, without making any material additions to the present plants, not less than 300,000 pounds. In fact selenium has, in recent years, gradually been brought more and more to the attention of the general public through its application to military uses and other purposes. In the glass industry, for example, it was used as decolorizer during the War period. It has been found that it imparts a violet red tint to the pyrex tubing after the latter has been used for a few combustions. The coloration is especially noticeable when a broken piece is examined. This may find an important place in the ceramic industry. In turning off the gas light of the city at day break, in controlling the draft of the factory chimneys, and in regulating the rapidity of the manufacture of sulphuric acid, the selenium cell is an important labor saving factor. In a similar way it is used in automatically lighting and extinguishing light buoys. It also finds application in photometry, wireless telephony, military telegraphy, and army signaling as well as for the transmission of signatures, handwritings, finger prints, and images in general(3)(4). The question of the vulcanization of rubber also should be considered. Some experiments have been published claiming the similarity of the action of selenium and sulphur on rubber(4)(5). The cost need not be prohibitive, since the supply could be easily increased and the price reduced provided there were a demand. In the personal experience of the writer, when working with the hydrogen selenide gas, the rubber connections of the apparatus soon turned red, and after a few hours were so clear a red that visitors to the laboratory imagined that the writer was using the ordinary red rubber connections. The rubber thus changed seems to be softer and more elastic than the original; this observation will be followed up. In this country the National Research Council has created a special committee of seven to investigate the various possible uses of selenium and tellurium. PHARMACOLOGICAL REVIEW