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February 4, 1974

Millimetric Misadventure

Author Affiliations

Harlingen, Tex

JAMA. 1974;227(5):558. doi:10.1001/jama.1974.03230180056026

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To the Editor.—  In a letter about an endotracheal tube (226:675, 1973), Karis said to cut 1.27-cm sections of the tube and later, to pull the catheter back 5.08 cm. Manifestly, Dr. Karis did not mean 1.27 cm and 5.08 cm, which would need to be measured by a caliper ruled at 0.1 mm. So why did he say 1.27 cm and 5.08 cm? The answer is that 1.27 cm is one-half inch, and 5.08 cm two inches.He had probably written "one-half inch" and "two inches," which was editorially converted into centimeters. In daily language, one inch means approximately one inch, and when Karis said "one-half inch" and "two inches," he was approximating.Systems of measurements based on anatomical standards (an ell, a span, a foot, a fingerbreadth, etc) are quite inexact, but in certain situations, its inexactity is its virtue. If you say "two fingerbreadths," the word "approximately"