The great contribution: Index Medicus, Index-Catalogue, and IndexCat

Objective: The systematic indexing of medical literature by the Library of the Surgeon-Generalʹs Office (now the National Library of Medicine) has been called ʹʹAmericaʹs greatest contribution to medical knowledge.ʹʹ In the 1870s, the library launched two indexes: the Index Medicus and the Index-Catalogue of the Library of the Surgeon-Generalʹs Office. Index Medicus is better remembered today as the forerunner of MEDLINE, but Index Medicus began as the junior partner of what the library saw as its major publication, the Index-Catalogue. However, the Index-Catalogue had been largely overlooked by many medical librarians until 2004, when the National Library of Medicine released IndexCat, the online version of Index-Catalogue. Access to this huge amount of material raised new questions: What was the coverage of the Index-Catalogue? How did it compare and overlap with the Index Medicus? Method: Over 1,000 randomly generated Index Medicus citations were cross-referenced in IndexCat. Results: Inclusion, form, content, authority control, and subject headings were evaluated, revealing that the relationship between the two publications was neither simple nor static through time. In addition, the authors found interesting anomalies that shed light on how medical literature was selected and indexed in ʹʹAmericaʹs greatest contribution to medical knowledge.ʹʹ