SKULL OF A HUMAN FETUS OF 40 MM. 399 



The nasal capsule resembles, roughly, a tent, partitioned into 

 equal, paired, lateral rooms or cavities by the septum, or meseth- 

 moid, which lies in the median sagittal plane of the skull. The 

 highest point, or peak, is marked by the crista galli. The roof 

 and sides are formed by the tectum nasi and paries nasi respec- 

 tively, the posterior or subcerebral portion of the former being 

 broken by the long, paired, irregularly-contoured fenestrae 

 cribrosae (fig. 1), destined to become the cribriform plate. This 

 portion of the superior surface of the capsule takes part in the 

 formation of the median part of the anterior cranial fossa, and 

 repres3nts the anlage of the upper surface of the ethmoid bone. 



The incomplete floor (fig. 2), or solum nasi, is formed laterally 

 by the inwardly-turned lower edges of the side-walls, and medially 

 by the lower border of the septum and the anterior paraseptal 

 cartilages. Between the side-wall and the septum is the gaping 

 and elongated basal fissure, which extends ventrally into the 

 incisura narina and dorsally into the cupuloseptal fissure, the 

 latter being a very narrow space between the dorsalmost extremi- 

 ties of the nasal septum and the nasal wall, almost completely 

 filled by perichondrium. The floor is almost entirely covered 

 in by membrane bones — the maxilla, the palatine and the vomer — 

 these closing off the inferior nasal meatus below, and marking the 

 upper delimitation of the oral region. The three elements, 

 tectum, paries and solum nasi, combine to form the shell-like 

 structure known as the ectethmoid. Laterally the dorsal por- 

 tion of this is in relation to the orbit. 



The nasal septum or mesethmoid (fig. 11) is a vertical and 

 roughly pentagonal plate of cartilage, constituting the ventral 

 end of the central stem of the chondrocranium. The dorsal 

 border is marked above by the interrupted line of attachment 

 of the dorsal surface of the tectum nasi, which separates the sur- 

 face of the nasal from that of the interorbital septum; below this 

 these surfaces have no definite delimitations. The cranio-dorsal 

 border, after passing over from that of the interorbital septum, 

 runs horizontally forward for a short distance, and then mounts 

 rapidly and evenly to reach the highest point of the chondro- 

 cranium in the conspicuous crista galli. The latter marks the 



