Coverpage of facsimile edition of 1899<unk> 's<unk>  of the Materia Medica The<unk> , referred to as The<unk><unk> , is the world's best-selling medical textbook, and the oldest continuously published English language medical textbook. First published in 1899, the current print edition of the book, the 20th Edition, was published in 2018. In 2014,<unk>  decided to move The<unk><unk>  to digital-only, online publication, available in both professional and consumer versions; this decision was reversed in 2017, with the publication of the 20th edition the following year. The<unk>  is one of several medical textbooks, collectively known as The<unk><unk> s, which are published by<unk>  Publishing, a subsidiary of the pharmaceutical company<unk>  Co., Inc. in the United States and Canada, and MSD (as The MSD<unk> s) in other countries in the world.<unk>  also formerly published The<unk>  Index, An Encyclopedia of Chemicals, Drugs, and Biologicals.
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