224 



HUMAN ANATOMY. 



fused in the adult, forming a rather dull inferior border continuous with the lateral 

 sharp one, they may remain distinct and enclose a well-marked fossa on the face just 

 below the nasal opening ; this is the fossa prcenasalis, rarely seen in other than low 

 races. Variations in the arrangement of these lines may occur, and according to 

 ZuckerkandV the line from the border of the nose may not always form the anterior 

 border of the fossa. The combined nasal openings, though in the main triangular, 

 may be roughly quadrilateral. More or less asymmetry is the rule. The nasal bones 

 and the nasal spine may point sideways, but not necessarily to the same side. The 

 spine points to the side on which the opening is the wider ; the broader aperture 

 usually does not descend so low as the narrower one. The tip of the nose is more 

 often turned to the right. In life the shape of the nose depends quite as much on 

 the soft parts as on the bones. 



The posterior openings of the nares, the choance, are remarkably symmet- 

 rical ; bounded above by the wings of the vomer, which conceal the body of the 

 sphenoid, on the sides by the internal pterygoid plates, internally by the vomer, 

 and below by the horizontal plate of the palate, each is much higher than broad. 

 The index of the choanae, showing the proportion of the breadth to the height 

 / loox breadth \ j^ ^^ j^^ ^^^ ^^^ ^ j^j. ^oj^en, showing relatively lower openings in 



\ height / ' 



the latter (Escat). Measuring the combmed breadth from one pterygoid process 



to the other at the hard palate on 

 Fig. 256. ten adult skulls irrespective of sex. 



Probe in infundibuium we found the average breadth 27.7 



centimetres and the average height 

 28.4 centimetres. The extremes 

 were 24 and 31 centimetres for the 

 breadth and 25 and 31 for the 

 height.^ The inclination of the 

 posterior border of the vomer is in 

 a general direct ratio to the degree 

 of prognathism,^ or the forward 

 projection of the face. 



Each nasal chamber (Figs. 

 255, 256) is very narrow, and 

 much higher in the middle than 

 at either orifice. The front part, 

 the vestibule, extends under the 

 bridge of the nose. The 7'oof is 

 extremely narrow except at the 

 posterior end. It is composed of 

 the nasal bones, thin below, thick 

 above ; of a small part of the frontal, a thin plate separating it from the frontal 

 sinus ; the very thin cribriform plate, easily broken ; the vertical anterior surface 

 of the sphenoid, pierced by an opening into the sinus ; and, finally, the wing of the 

 vomer. The floor is a smooth gutter, formed by the palatal processes of the maxillae 

 and palate bones. The lower border of the anterior nasal opening is higher than 

 the floor, so that an instrument has to be tilted over it. 



The anterior palatine canal opens through the floor near the front on either 

 side of the septum. The floor, except at the posterior part, is of strong bone, and 

 is smooth all over. The median wall is derived from a plate of cartilage, developed 

 at a very early period, from which the vertical plate of the ethmoid and the vomer 

 are also formed. A large quadrilateral space is left vacant in the macerated skeleton, 

 which in life is filled by the unossified portion of the original plate, known as the 

 trianirnlar cartilage. Apparently the process of ossification is excessive along the 

 line of union between the ethmoid and the vomer, since the adult septum is usually 

 bent to one side in its anterior two-thirds, thus making one nasal cavity much smallef 



Ethmoidal' 

 cells 



Middle 

 turbinate 



Inferior 

 turbinate 



Antrum 



Portion of anterior section of preceding skull, seen from be- 

 hind. The arrows occupy the opening from the antrum into the 

 hiatus semilunaris. 



' Normale und pathologische Anatomie der Nasenhohle, 2te Auflage, Vienna, 1895. 

 ' The development of the nasal cavity is described with that of the head. 

 • Escat : CavittS Naso-Pharyngiene, Paris, 1894. 



