56 PHYSIOLOGY OF THE HUMAN BODY. 
which the decaying matter of the body is carried away and fresh material 
supplied in its place. 
The process of Digestion may be divided into the following parts— 
1. The Mastication of the food; 2. The Insalivation; 3. The Deglutition 
or swallowing; 4. The Chymification or digestion in the stomach; 5. The 
Chylification or digestion in the intestines; and 6. The Absorption of the 
chyle. . 
1. Mastication or chewing is performed by the teeth. These are 
small, hard, white bodies, fixed in the jaws, so as to come against each 
other, and reduce the food by cutting and bruising it. They are formed 
of three substances—dentine, cement, and enamel. The inside and body 
of the tooth are formed of dentine, so called from Latin dens, dentis, a 
tooth ; outside of this is a layer of cement, which is softer than dentine; 
but where the tooth appears above the jaw, the cement is replaced by 
a hard enamel, which forms a very strong protection for the exposed 
part of the tooth, called the corona [Latin, ‘a crown’]. ‘There are in 
all 32 teeth in man, and these are of three kinds: the incisive! or 
cutting teeth, in front; the canine? or dog-teeth, next to the cutting- 
teeth on each side; and the molars? or grinders, behind, ordinarily called 
double teeth, because they have 
a double edge, instead of a single 
one like the front teeth. The 
incisors have a single fang or 
root, and the corona is bevelled 
behind, so as to present a sharp, 
chisel-like cutting edge. There 
are two on each side of both 
jaws, that is, eight altogether, and 
they are used for biting the food, 
aa, fig. 51. The canine teeth, 
so called because they are very 
prominent in dogs, have a single 
root, and their corona is more 
pointed than edged, bb, fig. 51. 
The molars are divided into true 
and false. First come (in a half- 
jaw, as A, fig. 51) two false molars — 
or premolars,* so called because they are placed before the true molars, ¢, 
which are of a form between that of the canine teeth and the true molars. 
Last of all come the true molars, d, which are larger than any of the 
other teeth, and have a corona well adapted for bruising the food. 

1 Fram Latin ineido, ineisum, to cut. 2 From Latin canis, a dog. 
3 From Latin malo, to grind. 4 From Latin pre, before. 
