The electronic version of the current edition of the Merck Index contains a diverse collection of over 11,500 short articles. More than 4,000 articles are devoted to a wide variety of drugs and pharmaceuticals, over 2,000 describe common organic chemicals and laboratory reagents, and another 2,000 cover naturally occurring substances and plants. An additional 1,000 articles focus on the elements and on inorganic chemicals. Almost 1,000 pertain to compounds of agricultural significance, and several hundred describe endogenous substances and biological agents. Most include basic physical properties, toxicity information and references to syntheses and uses. There are also tables of named reactions in chemistry and other useful information. The Merck Index may be searched by chemical name, properties and by chemical structure or substructure.