THE STRUCTURE OF THE HUMAN SKULL. 



127 



But if, with a fine saw, the greater part of the perpendicular 

 plate of the palatines, and the corresponding part of the maxil- 



laries, and, with those, their palatine plates, bo cut away, 

 leaving only the premaxillae, vomer, and upper parts of the 

 maxillary and palatine bones ; it will be found that hinder 

 nares are left, which entirely correspond with the " posterior 

 Dares " of a bird or of an amphibian ; that is to say, they are 

 passages between the vomer in the middle line, the premaxillae 

 and maxilla? in front and externally, and the palatines ex- 

 ternally and behind. 



Fio-. 54. 



b'ig. 54. — The base of a human skull — the nasal, ethmoid, vomerine, maxillary, palatine, and 

 pterygoid bones being cut through horizontally, and their lower portions removed. 

 The entire right maxilla is taken away. The posterior pair of letters, JViV, are situated 

 in the median nares, which are incomplete, in fiont, in consequence of the removal of 

 the premaxillae. 



In fact, the apertures of the nasal chamber into the mouth, 

 thus artificially exposed, are those which originally exist in 

 Man and the higher Vertebrata ; but the downward growth of 

 the maxilla into its alveolar process, and of the palatine bone 

 into its perpendicular plate, together with the production inwards 



