Harelip is a congenital deformity of the upper lip, characterised by a cleft extending for a variable depth, either through the soft tissues of the lip only, or implicating in addition the alveolus, floor of the nose, and palate. No mention of this condition is made by Hippocrates, Galen, or any of the fathers of medicine; and so far as I can discover the name is first used by Ambrose Paré, who probably initiated the treatment by pin and figure-of-8 suture. The name is really a misnomer, in that the condition (as has been many times pointed out, but notably by Fergusson) does not simulate a hare’s lip except in the fact of being cleft, for the natural cleft in the animal’s lip is always in the median line below, bifurcating above to reach either nostril (Fig. 1), whereas in the abnormal human lip the cleft lies to one or the other side. Instances of median defect are known, but they are extremely uncommon, and consist often of more than a simple fissure. [Illustration: FIG. 2. FIG. 3. FIG. 4. FIG. 5. FIG. 6.] The deformity may exist as a simple notch in the soft tissues of the lip, unilateral (Figs. 2 and 3) or bilateral (Fig. 4); when more decided, it may implicate one or both nostrils (Figs. 5, 6, and 7). In mild cases the alveolus is intact; in others, cleft, constituting the variety known as _alveolar harelip_, and the line of fissure may, or may not, extend backwards into the palate. In all cases of double alveolar cleft, the palate is also involved, and the central parts of the lip and intermaxilla tend to project forwards; in the severest forms these portions are completely isolated from the maxillæ, and, supported by the vomer and septum nasi, form a proboscis-like appendage to the end of the nose, which is excessively disfiguring. (Figs. 7 and 8 illustrate this deformity as seen from the front and in profile.) The shape of the nose in unilateral harelip is very characteristic, being broad and flattened out from the deficiency of the floor and posterior wall of the anterior nares. [Illustration: FIGS. 7 AND 8.—Double harelip with projection of the os incisivum, as seen from the front and in profile. (_Fergusson._)] Harelip seems to occur more commonly in boys than in girls. According to Müller, out of 270 cases, 170 were boys, and 100 girls.