Figure 18: Diagram of the cartilage thickness of the septum at the age of 6 weeks, in relief. Sphenodorsal and sphenospinal zone of thick cartilage and the thinnest area lies at the anterior end of the septum; l.green = 50–250 µ, d.green = 250–450 µ, l.red = 450–650 µ, d.red = 650–850 µ (see 2.3.1).