Classification of Special Materials
19th Century Works and Early Printed Books
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At NLM, works published prior to 1914 are classed either in the 19th Century Schedule or the WZ (History of Medicine. Medical Miscellany) Schedule. The rules for classifying pre-20th century works also apply to reprints and facsimiles of these works.
19th Century Schedule
The 19th Century Schedule is a simplified subject classification developed in 1956 that is derived from the letters that represent the preclinical and clinical subjects covered by the NLM Classification used for 19th century (1801–1913) materials. It is also used for monographs and serials (except for bibliographies which follow the classification for modern bibliographies).
WZ Schedule
The entire WZ Schedule is used for non-clinical 19th century works.
When the subject falls outside of the scope of the schedules of the NLM Classification, only the letters of the LCC schedule representing the subject are used. WZ 230–270 is reserved for Early Printed Books. This includes works published before 1801 and Americana (i.e., early imprints from North, South, and Central America and the Caribbean Islands). These numbers are used only for original publications. Reprints and translations of pre-1801 works are classified in WZ 290 292, and modern criticism of early works in WZ 294.
Exceptions
These rules do not apply to new editions of early printed works which are classed in the main schedules by topic.
Some 19th century works are classed in the W6 pamphlet collection and do not use the 19th century schedule.
For additional guidance on 19th Century Works and Early Printed Books, visit the NLM Policy on Classification.