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Scope of Revision

Historical Development

Structure of the NLM Classification

Relationship to MeSH®

Index

Scope of Revision

This edition incorporates all 2009 additions and changes to the schedules (see Class Numbers Added and Canceled) and to the index, which has been newly edited and updated with appropriate MeSH concepts. Eighty-one new index entries were created of which thirty-four are from the 2009 MeSH; the remainder are MeSH terms from previous years. Numerous main index entries and cross references were modified to reflect changes in the MeSH vocabulary.

Although the broad nature of the NLM Classification schedules precludes complete correspondence with MeSH, new class numbers were added and existing class numbers were canceled as needed to reflect other changes in MeSH and the biomedical and related sciences literature cataloged.

The W (General Medicine. Health Professions), WZ (History of Medicine. Medical Miscellany), and 19th Century schedules were the major areas of focus for the 2009 edition, along with Table G.

The header titles of the W and WZ schedules were augmented to better reflect the contents of the schedule:

• W was changed from Health Professions to General Medicine. Health Professions.
• WZ was changed from History of Medicine to History of Medicine. Medical Miscellany.

Some W, WZ, and 19th Century class number captions and notes were revised to better reflect the scope of the number. For example:

• At W 20.5, the caption Medical research was changed to Biomedical research.
• At W 10, the following note was added: Classify works on travel medicine at WA 108.
• At WZ 350, the caption Literary and artistic works by physicians and other association items was changed to Literary and artistic works by health professionals and associations.
• At WBA, the caption Popular medicine was changed to Popular medicine. Domestic medicine.

Table G (geographic breakdown) is now permitted with W 84.6 Primary health care.

Class number captions were also revised in other schedules. For example:

• At WE 259, Osteochondrosis was added to the caption.
• At WB 102.5, Evidence-based medicine was changed to Evidence-based practice.

Instructional notes were added or modified to clarify classification practices as needed, e.g., a note was added to WA 292: Classify works on wilderness medicine in WB 107.

A new Table G Section was created for historical jurisdictions or entities that existed in the past and whose former territories are not encompassed by a single present day country. Some of the jurisdictions listed in this section were removed from the Obsolete Table G Notations section. Some cutters of present day countries are also being used for the historical lands even though these are not one-to-one matches. For example, GR9, the cutter assigned to Russia (Federation), is also assigned to the USSR and Russia (Pre-1917).

Historical Development

The genesis of the NLM Classification is a Survey Report on the Army Medical Library, published in 1944, which recommended that the "Library be reclassified according to a modern scheme," and that the new scheme be a mixed notation (letters and numbers) resembling that of the Library of Congress. Subsequently a classification committee was formed, chaired by Keyes D. Metcalf and including Mary Louise Marshall who compiled the schedules. Medical specialists acted as consultants to the committee. Based on the consultants' advice, that of the committee and of the NLM cataloging staff, Ms. Marshall produced a preliminary edition of the Library's Classification, which was issued in 1948.

The preliminary edition was revised by Frank B. Rogers and the first edition of the new classification was published in 1951 as the U.S. Army Medical Library Classification. It firmly established the current structure of the classification and NLM's classification practices. The headings for the individual schedules were given in brief form (e.g., WE - Musculoskeletal System; WG - Cardiovascular System) and together they provided an outline of the subjects that constitute the National Library of Medicine Classification . These headings were interpreted broadly as including the physiological system, the specialty or specialties connected with them, the regions of the body chiefly concerned and subordinate related fields. Within each schedule, division by organ usually has priority. All schedules, including some of their sections, are preceded by a group of form numbers representing publication types. These numbers, ranging generally from 1-39, are employed as mnemonic devices throughout the Classification.

Beginning with the 2002 edition, the National Library of Medicine Classification is published in electronic form and updated annually:

The online environment offers many advantages to users including hyperlinks between class numbers in the index and the schedules, and between terms within the index and direct links from these to the MeSH record itself under the MeSH Browser.

The online data creation and maintenance system of the Classification gives NLM the ability to update the classification annually in tandem with MeSH. Publication of printed editions ceased with the 5th revised edition, 1999. Beginning with the 2006 edition, the NLM Classification is available in PDF (Portable Document Format) at http://www.nlm.nih.gov/class/terms_cond.html.

Structure of the NLM Classification

The National Library of Medicine Classification covers the field of medicine and related sciences, utilizing schedules QS-QZ and W-WZ, permanently excluded from the Library of Congress (LC) Classification schedules. The various schedules of the LC Classification supplement the NLM Classification for subjects bordering on medicine and for general reference materials. The LC schedules for Human Anatomy (QM), Microbiology (QR) and Medicine (R) are not used at all by the National Library of Medicine since they overlap the NLM Classification.

Relationship to MeSH

The schedules with their special requirements for use with all types and forms of materials preclude strict adherence to the hierarchical arrangement of the Medical Subject Headings (MeSH), the Library's thesaurus for indexing and cataloging. The schedules maintain their own character in order to provide for material, old as well as new, acquired for the Collection, including dictionaries, atlases, directories and other items, which are not suitable for the arrangements, found in MeSH. However, an effort was made to make schedule headings, subheadings and class number captions compatible with MeSH terminology. The MeSH Tree Structures were used extensively to determine the proper placement of a concept in a schedule and to relate index headings to one another. Since the representation of subjects in the schedules of the NLM Classification is intentionally broad, the captions do not enumerate all of the subordinate concepts that are to be classified in a given number. MeSH descriptors for these subordinate concepts do appear in the index, to the extent practical with appropriate references to the classification numbers.

Index

The Index to the NLM Classification consists primarily of Medical Subject Heading (MeSH) concepts used in cataloging. It includes concepts first appearing in the latest edition of MeSH and other older concepts as warranted by the literature cataloged. It also provides access to classification numbers through these MeSH concepts. Index entries are updated annually to reflect additions and changes of the latest edition of MeSH. For additional information on the Index see About the Index.