680 REPRODUCTION. 



forming a complete separation between the oral and nasal cavities. 

 The right and left nasal passages are separated from each other by a 

 vertical plate (vomer), which grows from above and fuses with the 

 palatal plates below. Fissure of the palate is caused by a deficiency 

 of one of the horizontal plates. It is accordingly situated a little on 

 one side of the median line, and is frequently associated with hare-lip 

 and fissure of the upper jaw. 



The anterior and posterior arches of the palate are incomplete trans- 

 verse partitions which grow from the sides of the fauces, subsequently 

 to the perforation of the pharynx and its communication with the oral 

 cavity. Owing to the muscular tissue which they contain, the orifice 

 of the alimentary canal thus becomes capable of constriction or enlarge- 

 ment, according to its condition of functional activity. 



