598 DEVELOPMENT [CHAP. XLII. 



by the external angular processes of the frontal, the small wings of 

 the sphenoid, and the frontal bone-, itshcemal arch, by the tympanic 

 portion of the temporal bone, and by the articular and dental portion 

 of the inferior maxilla. 



The body of the rhinencephalic or nasal vertebra is represented by 

 the vomer ; its neural arch, by the ossa plana of the ethmoid, and by 

 the nasal bones ; its hcemal arch, by the palatine, pterygoid, and 

 malar bones, by the squamous and zygomatic portion of the temporal 

 bones, and by the superior maxillary and intermaxillary bones. 



In thus briefly describing the manner in which the cranial 

 vertebrae are constructed, we feel great regret that our limited 

 space will not permit us to enter more at length into the beautiful 

 and well-known discoveries of Professor Owen in this department. 

 We cannot too strongly recommend the reader to consult upon 

 this important subject, Professor Owen's " Archetype Skeleton," 

 and his " Homologies of the Vertebrate Skeleton." 



Development of the Face and Visceral Arches. The visceral cavity 

 in the upper part of the embryo, at a very early stage of develop- 

 ment, is bounded above by the cerebral capsule ; and below, and 

 at the sides, by the anterior visceral arch. Reichert has shown 

 that this arch becomes bent upon itself, and from it are formed 

 above the angle, the superior, and below the angle the inferior, 

 maxillary apparatus. 



The superior maxilla grows upwards, and unites with a promi- 

 nence which is seen in the centre of the forehead, ike frontal pro- 

 cess of Von Baer a space being left between the two superior 

 maxillae, which becomes the nasal cavity. Beneath this, the two 

 bones are connected together by the partition which forms the 

 palate, and which does not appear for some time. 



In animals, besides the maxillary bones, there are a pair of 

 narrow bones between them, extending from the interval between the 

 lower portion of the nasal, and the ascending process of the superior 

 maxilla. These are the intermaxillary bones, which exist in the hu- 

 man foetus in a rudimentary condition. They appear to be formed 

 partly from the nasal process of the forehead, and partly from a por- 

 tion of blastema which is detached from the lower jaw, to which 

 Reichert gives the name of intermaxillary rudiment. Tri man this 

 bone is not developed; but in fishes and amphibia it contains 

 teeth. The intermaxillary bones differ, therefore, in their origin, 

 from the maxillae, and are probably developed from centres inde- 

 pendently of the latter. In the monstrosity familiar to us as hare- 

 lip, the superior maxillae and palate bones of opposite sides do not 



