A STUDY OF BLOOD MANUFACTURE 77 



1. THE MOUTH CAVITY 1 



Walls of the Mouth Cavity. The cavity of the mouth is 

 inclosed at the sides by the muscles of the cheek. The roof 

 of the mouth is formed by a horizontal plate of bone (easily 

 felt by the finger or the tongue), called the hard palate. 

 This separates the cavities of the mouth and nose. Near 

 the back of the mouth the hard palate ends abruptly, and 

 the partition between these two cavities is completed by the 

 soft palate. The muscular tongue helps to form the floor of 

 the mouth cavity. 



Mucous Membrane. If, by the aid of a hand mirror, one 

 looks within one's mouth cavity, one finds it lined with a soft, 

 moist covering of a pink or red color. This is called mu'cous 

 membrane. It is much thinner than the outside skin, and 

 many blood vessels lie just beneath it. To these facts is 

 due its red color. Much of the moisture that covers the 

 inner lining of the whole alimentary canal is the slimy 

 mucus secreted by the gland cells of the mucous membrane. 



2. THE TEETH 2 



Arrangement of the Teeth. Within the mouth cavity the 

 solid food is cut into small 

 pieces, mixed with the juices 

 of the mouth, and then ground 

 into a pulpy mass. A large 

 part of this work is done by 

 the teeth, which are arranged 

 in two semicircular arches. 



They are set in sockets formed 



i , P , FIG. 24. Number and Positions 



in the bone ot the upper and of Teeth of Permanent Set. 



lower jaws. The region of the 



jawbones where the teeth are imbedded is covered by the 



gums. 



1 See "Laboratory Exercises," No. 17. 



2 See "Laboratory Exercises," No. 17. 



