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Show ! \ l \ I I \ I ) l 126 sphenoid and with the vomer; while the outer, or orbital, processes articulate with the so-called lateral Jnasses of the ethmoid and with the maxilla; so that the upper part of each palatine bone is directed, from the cranio-facial axis, with which its inner end is connected, outwards and forwards (Fig. 54). rrhe third pair of bones, the Pterygoids, are the internal pterygoid processes,-bones which are original~y quite distinct from tho sphenoid, while the external pterygoid proce~ses nre. of a v~ry different character, being mere outgrowths of the absphenmds. These are connected with the basi-sphenoid (or rather with the lingulce sphenoidales), above, and, in front, with the palatines, while their planes are directed backwards and smnewhat outwards. The fourth pair of pre-oral bones-the Marcillm-are connected in front and internally with the premaxillm, and behind and internally with the palatiues, hut they nowhere come into direct contact with the cranio-facial axis, at least primarily. I make the latter qualifiration because th vom r articulates with the superior surface of the palatine plates of tbe maxillm, and it may be said that, in this way, the maxillre do unite with the cranio-facial axis. This articulation, however, has nothing to do with the primitive connections of the bones, but depends upon a 1nodification of the maxillre peculiar to the higher vertebrata. The bony apertures-called "posterior nares "-in Man, for exmnple, are structures of a totally diffi rent cbnractor from, and superadded to, what are called the posterior nares in a frog, or ordinary lizard, or bird. In these lower V ertebrates, the posterior nares are apertures, bounded on the inner side, by the vomer; on the out r side and behind, by tho palatine bones; in front, by the premaxillro and maxillre. In Man, on the other hand, the apertur s so call d are limited, it is true, on the inner side by th vorner, and on tho outer side by the palatine bones; but they arc al. o bound d below and in front by the palatine bonos, and the pr maxillm and maxmm have nothing to do with then1. On looking closely into the matter, however, it will be found that that region of tho palatine which forms the outer and inferior boundary of the posterior nares of Man is a something which bas no representative in the lower V ertebrato. 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 maxillaries, and, with these, their palatine plates, be cut away, leaving only the premaxilloo, vomer, and upper parts of the 1naxillary and palatine bones; it will be found that hinder nares are left, which entirely correspond with the "posterior nares " of a bird or of an a1nphibian; that is to say, they are passages between the vomer in the middle line, the premaxillre and maxilloo in front and externally, and the palatines externally and behind. Fig. 54. A Fig. 54.-T~e base of a l~uman sku 11-the nasal, ethmoiu, vomerine, maxillary, palatine, and r,terygo~d b?nes bem.g c~t through horizontally, and their lower portions removed. ! he entire nght maxilla IS taken away. The posterior pair of letters, NN, are situated 111 the median nares, which are incomplete, in front, in consequence of the removal oC the premaxillre. 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 rrtaxilla into its alveolar process, and of the palatine bone into its perpendicular plate, together with the production inwards |
