The fact that these centers of development are concerned in the formation of the parts involving harelip accounts for the position of the cleft in the lip as being unilateral or bilateral, and rarely if ever median or intermaxillary. CLASSIFICATION OF HARELIP DEFORMITIES Six varieties of harelip deformity are recognized by Rose, but herein only five classes of these will be considered, one of which, the first, is so rare that its occurrence is practically denied. For all purposes in surgery of the face, in which cosmetic effects are sought, the author considers the following classification to answer fully: 1. Median or intermaxillary cleft. 2. Single and double cleft. 3. Facial cleft. 4. Buccal cleft. 5. Mandibular cleft. [Illustration: FIG. 147.—MEDIAN CLEFT. (Engle’s case.)] [Illustration: FIG. 148.—MEDIAN CLEFT WITH RHINOPHYMIA. (Trendelenburg’s case.)] =1. Median or Intermaxillary Cleft.=—As has been said, the first variety of this form of lip deformity is very rarely met with. It consists of a cleft in the median third of the upper lip, more rarely associated with the absence of the intermaxillary bone and total cleft of the hard and soft palate. In fact, the entire median section may be absent with or without absence of the intermaxillary and vomer bones (Engle) (see Fig. 147). Commonly, however, the cleft involves only a part of the filtrum of the lip, although Witzel speaks of a case in which the lip assumed the form of a dog’s nose, the cleft extending upward, completely dividing the nares from one another, or the entire nose may be divided in its median line. When the cleft involves the hard parts—that is, the intermaxillary bone and the hard palate—it is said to be total. =2. Single and Double Cleft.=—The second variety in the above classification is by far the most common, and is often, therefore, termed ordinary. In this there exists either a unilateral or bilateral cleft of the lip of varying degree, depending upon the involvement of the tissue affected. It is not unusual to find fissures in these cases extending through the alveolar arch and the hard and soft palate. This fissure or cleft is always found on one side of the median line, while in the soft palate it is median. Most unilateral clefts of the lip will be found to be in the left outer third. They are more common in the male child. [Illustration: FIG. 149. FIG. 150. FIG. 151. TYPES OF UNILATERAL CLEFT.]