About the Classification Index
- How to Use the Index
- Relationship to MeSH®
- Cross References
- See References
- Pointing to a Single Index Term
- Indented under Index Terms
- General References
- See Also References
- Under Indented Terms
- To General Terms
- Drugs, Chemicals and Biological Agents
The Index to the National Library of Medicine Classification consists of Medical Subject Headings (MeSH). Some non-MeSH terms are used as cross references when no appropriate MeSH term is available. All MeSH entries in the Index are updated annually to be consistent with the latest edition of MeSH. The index terms are arranged in alphabetical order with Roman numerals filed as letters in this arrangement. Arabic numerals are found at the beginning of the Index.
The classification numbers assigned to the index terms are usually general numbers for the concept represented or numbers reflecting a medical view when that is more appropriate.
Indented terms represent more specific aspects of the subject or aspects of the subject to which a number different from the general number has been assigned. The indented terms are often elliptical and should be interpreted broadly. For example, when "Organic chemistry" is used as a term indented under the name of a chemical, the number following it is to be selected if the principal focus of the work being classified is the organic chemistry of the chemical. Some subheadings refer the user to another heading. General references or see also references are listed at the end of the alphabetical sequence of the indented terms under the index term.
- Electrodes QD 571
- Biomedical engineering QT 36
- In electric stimulation therapy WB 495
- Used for special purposes, by subjects, e.g., in Urinalysis QY 185
- See also Microelectrodes QT 36, etc.
Library of Congress (LC) numbers are assigned to subjects that fall outside the scope of the NLM Classification. When a concept represented in MeSH has no exact equivalent in LC's schedules a number was selected that fit the concept most closely. Since NLM rarely uses LC's K (Law) schedules the numbers provided for index terms relating to laws are for the subject rather than the law.
The Index is not a substitute for the main schedules. A user should always refer to the schedules for confirmation of the proper application of the number and its relationship to other numbers.
Many headings are assigned a range of numbers rather than a specific number. The schedules of the NLM Classification or the Library of Congress Classification are the only source of the meaning of specific numbers within the range.
The number assigned to a heading in this Index should not be used unless it represents the principal subject of the material being cataloged.
The Index represents only those MeSH terms that are linked to NLM or LC classification notation. The Index does not include all MeSH headings found in the Medical Subject Headings Annotated Alphabetic List or the MeSH Browser and it is not a substitute for these.
When assigning MeSH headings to a work the Annotated Alphabetic List or the MeSH Browser must always be consulted. The Index does not provide annotations nor does it show relationships between headings; these are found in the Annotated Alphabetic List and the Tree Structures, respectively, or the MeSH Browser. To view MeSH descriptor data, when available, click on the "tree" icon on the left of the index term, which links to the term in the current Browser.
The number of indented terms under an index term varies greatly. The choice was dependent upon the needs that arose in the past. Therefore, the list is in no way exhaustive of the possibilities that can occur.
The Index contains over ten thousand index terms to which classification notations are assigned. Many terms are found only in the index and will not appear in the schedules. They refer to a number in the schedule where only a broader term or a related term appears.
There are several types of cross references used in the index.
A see reference points to a single index term or concept.
- Acquired Immunity see Immunity
See references that are indented under index terms link the concept to a more specific index term.
- Developing countries WA 395
- Mental see Mental Health WM 105, etc.
- Oral see Oral Health WU 113
- Public see Public Health WA
General references following all indented terms or concepts relate to the main index term or concept. Examples of general references are: "Used for special purposes, by subject, " " Specific types of [topic], by subject," etc.
- First aid WA 292
- Hospital programs see Disaster Planning WX 185
- Specific types of disaster, by subject
- See also Civil Defense UA 926-929, etc.
A See also reference provided under an indented term relates only to the indented term. When the See also reference is related to the main index term only it follows all indented terms and general references. The latter is represented in the Disasters example above (See also Civil Defense UA 926-929, etc.). The former is represented here.
- Alcoholic beverages HF 6161.L46
- Pharmaceutical QV 736
- See also Drug Labeling QV 835
- Tobacco HF 6161.T6
- Other special subjects, by business in HF 6161 or other appropriate number
See also references lead the user from one index term to a related index term under which are listed indented terms that apply equally to both headings.
- Accidents, Occupational WA 485-491
- Of the eye WW 505-525
- See also special topics under Accidents
- First aid WA 292
- In anesthesia WO 288
- Medicolegal aspects
- Cause of death W 843
- Disability evaluation W 900-925
- See also Insurance, Accident W 100-250, etc.
Note when "etc." follows a number in any type of reference, it indicates that in addition to the numbers given in the reference, there are other numbers which also represent the index term. The user will find these other numbers listed under the index term. For example, the see also reference, under Accidents, to "Insurance, Accidents W 100-250, etc.," indicates that under the index term "Insurance, Accident" there are other class numbers in addition to the range W 100-250.
The numbers provided after index terms for drugs, chemicals and biological agents represent their biochemical, pharmacological or chemical properties. The index rarely gives a number for these agents when the material being cataloged discusses their use in the therapy of a particular disease or in a particular study. In such cases the material is classified with the disease or the subject of the study.