8 ANIMAL PHYSIOLOGY. 



flattened as if composed of two combined, and have each 

 two openings at the extremity. 



57. In infancy the teeth begin to cut the gums about the 

 seventh month, the central incisors appearing first, and the 

 others in order backwards, with the exception that the first 

 milk-molar precedes the eye-tooth in front of it. The last 

 of this series, the second milk-molars, appear about the end 

 of the second year. The next teeth to appear are the first 

 true molars, sometimes called the five-year old teeth; then, 

 about the seventh year, the milk teeth begin to drop by 

 absorption of the fangs, and the permanent teeth to come 

 up above the gums in their place. The changing of the teeth 

 begins in front, and goes regularly backwards, with the ex- 

 ception that, as in the first dentition, the canines are delayed, 

 both bicuspids making their appearance before the permanent 

 canines come up, about the twelfth year. Soon afterwards, 

 the second molars cut the gums, and lastly, at very variable 

 periods, often a number of years later, the third molars, or 

 wisdom teeth, come to the surface. 



58. Course of the Ingesta. The mouth, or buccal cavity, 

 as it is technically called to distinguish it from the opening 

 of the lips, is walled in by voluntary muscles of the face; 

 within the arches of teeth it has the tongue in its floor, and 

 its roof formed by the palate, which separates it from the 

 nasal cavity, while it communicates behind with the throat, 

 by a constricted part called the fauces. The arch of the 

 fauces is limited above by a prolongation backwards of the 

 palate, consisting of soft parts unsupported by bone, and 

 termed the soft palate or velum palati. This has a free edge 

 directed backwards, and prolonged into a pendulous structure 

 in the middle, called the uvula, while on each side descend 

 from it two prominences, the anterior and posterior pillars 

 of the fauces. Between these are placed the glandular-look- 

 ing bodies known as the tonsils, structures of obscure func- 

 tion, but sometimes troublesome by enlargement, or by 

 inflammation and ulceration in sore throat. 



The cavity behind the fauces is called the pharynx. It 

 is surrounded behind and on the sides with constrictor 

 muscles, while in front it communicates with a number of 

 openings. It extends above the soft palate to the base of 



