THE MOUTH AND THE TONGUE 537 



palatine canal, behind the upper incisor teeth, where, to 

 our mind, the nasal floors, with the organs of Jacobson, 

 empty themselves by capillary openings in the extremities 

 of the ducts penetrating the canal. The organs of Jacob- 

 son empty themselves into the inferior nasal passages 

 just, or almost, over the entrance to the ducts known as 

 leading through the anterior palatine canal, and may, at 

 an early period of life especially, or when these ducts are 

 said to be patent, find a ready channel, or channels, 

 through which to gravitate, or be sucked, through capillary 

 tubes into the cavity of the mouth, exactly at the spot 

 required to meet the difficulty in question. 



Terminating by somewhat capillary exits, the process 

 of evacuation of the ducts, or the flow of the fluid from 

 the nose through them, may be constant or interrupted, 

 according to the position, degree of dryness of the 

 surfaces, and whether they are opposed or unopposed, 

 as well as the changing necessities of the parts, arising 

 from whether they are at rest or in action ; it is accom- 

 plished, or attained, by the sucker-like action of the lingual 

 surface on or against the roof of the mouth when the 

 intervening air is expressed, as it is when the two sur- 

 faces, lingual and palatal, are intimately opposed to, and 

 then withdrawn from, each other, as is to be observed 

 during infant sucking, and many of the movements, infan- 

 tine and adult, peculiar to the lingual organ in its to and 

 fro apposition with the roof of the mouth. Who has not 

 noticed the great advantage and comfort of a preliminary 

 and timely moistening of the two surfaces in question 

 when the tongue has to be used for almost any purpose 

 alimentary or linguistic, or even for passively "chewing 

 the cud of reflection." 



In the economy of mastication and preparation of the 

 food for deglutition the roof of the mouth may be likened 

 to an inverted " nether millstone," against which, when 

 the food is being ground down by the teeth and insali- 

 vated by the various glands, the tongue is constantly 

 engaged triturating and reducing it to a pulp capable of 

 being swallowed and passed into the stomach in a condition 

 suitable for gastric digestion. The rigid surface of the 

 hard palate thus becomes a valuable asset in the economy 



