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May 1969


Arch Intern Med. 1969;123(5):598. doi:10.1001/archinte.1969.00300150116020

The editor forwarded Dr. Thompson's letter to Dr. Sullivan for comment.

To the Editor.  —I appreciate the concern about the proper use of the term hippus. As clearly pointed out, hippus has been relegated to the clinically meaningless role of defining abnormal degrees of pupillary unrest. Indeed, with the exception of the article by Cannon et al,1 hippus has been reserved to signify rapidly occurring transient pupillary changes. We were moderately concerned that the duration of the pupillary changes during Cheyne-Stokes breathing that we described was too long to fit the classical concept of hippus. However, Cannon et al had previously used the term to signify the more prolonged pupillary alterations occurring during a complete respiratory cycle (approx five seconds in duration). Their experimental findings, though of questionable significance, benefitted by receiving a catchy name and thereby have been widely quoted. We feel that the current lack of appreciation