The importance of the nasal septum in man is self evident to the rhinologist. It divides the nasal cavity into two lateral passageways and thus forms the mesial wall of each nasal fossa. It also determines the line of the nasal dorsum.In primitive races and in Caucasian children the nasal septum is usually straight and symmetric, but among Caucasian adults it frequently deviates. This deviation usually concerns the cartilage and the ethmoid portion, leaving the vomer normal or nearly so. Schaeffer 1 considered the perpendicular plate of the ethmoid bone (mesethmoid), which forms the cephalic third of the septum, of particular interest in septal deviation. The extent of the mesethmoid is variable, and the septal cartilage is correspondingly large or small.During fetal life, infancy and early childhood, the nasal septum is usually symmetric and occupies the midline throughout its extent. Asymmetry has, however, been seen in early childhood, and marked deviation has been observed in some fetuses.Deflection of the nasal septum in adults is so general as to be considered an almost normal condition. This deviation may vary from slight irregularities to those which entirely occlude one of the nasal fossae. In spite of these facts, many adults have essentially symmetric nasal septums.Sheehan2 pointed out that, regardless of the variations in the nasal framework which may account for its deformity, the first essential step is to return the nasal septum to its normal position. Since the septum separates the air passages and establishes the line of the dorsum, regardless of the degree of its deformity or weakening, it must be restored to fulfil these requirements before the other parts of the nasal framework can be adjusted effectively. The cartilage cannot be made straight without excision, and the amount of excision must vary according to the degree of the bend in the cartilage. Unless and until the septum has been set and straightened, nothing can be done toward assuring a correct line for the dorsum. EMBRYONAL DEVELOPMENT OF THE NOSEThe human nose develops from anlages (nasal placodes) which appear about the fifth week of fetal life as thickenings of the ectoderm just above the oral plate of the embryo. The centers of these ectodermal thickenings become depressed by the rapid growth of the surrounding tissue, and in this way the early nasal pits are formed ( fig. 1). For a short time the nasal pits open into the oral cavity. The primitive external nose is formed during the early development of the embryonic facial region. At the time of the fusion of the maxillary and the median nasal processes, the nasal pits become entirely sepa¬ rated from the oral fossa. A secondary connec¬ tion with the roof of the primitive oral cavity appears in the 4 to 5 day embryo, due to thinning and final rupture of the bucconasal membranes, by which the primitive nares (choanae) are formed. Following this, the upper part of the oral cavity becomes continuous with the nasal cavity, owing to the formation of the palatal processes of the maxil...

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