National Library of Medicine Classification (NLM)
The National Library of Medicine Classification covers the field of medicine and related sciences. It uses a system of mixed notation patterned after the Library of Congress Classification [link to LCC page] where alphabetical letters which denote broad subject categories are further subdivided by numbers. The NLM Classification utilizes schedules QS-QZ and W-WZ, permanently excluded from the LCC Schedules and is intended to be used with the LCC schedules which supplement the NLM Classification for subjects bordering on medicine and for general reference materials. The LCC 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.
The NLM Classification is hierarchical, and within each schedule, division by organ usually has priority. Each main schedule, as well as some sections within a schedule, begins with a group of form numbers ranging generally from 1-49 which are used to classify materials by publication type, e.g., dictionaries, atlases, laboratory manuals, etc.
The main schedules QS-QZ, W-WY, and WZ (excluding WZ 220-270) are used to classify works published after 1913; the 19th century schedule is used for works published 1801-1913; and WZ 220-270 is used to provide century groupings for works published before 1801 and Americana. Geographic subdivision is provided for certain subjects in the NLM schedules by the application of Table G notations.
Outline of NLM Classification
Medicine and Related Subjects: