DURING operations on 3 patients with double harelip, a modification of one of the usual plastic procedures was evolved.1 The essential feature of this change was to join the sphincter muscles of each side across the premaxilla, and, to this end, it was necessary to cut deeply into the lip at right angles to its edge in order that a flap of sufficient length could be sewn to the corresponding structure of the opposite side. What was not known at the time was how much sphincter oris muscle was present. It is the purpose of this article to give the anatomy of this muscle in double harelip.
The structure of the orbicularis oris muscle in the lower lip is of little concern in this report. Nor is there much to say about the lip portion of the premaxilla except to record in agreement with Ritchie,2 Veau and Plessier,