ORGANS OF DIGESTION. 121 
The submucous or areolar coat is adjacent to the mucous 
coat of the intestine, but in the stomach the muscularis 
mucose intervenes. Next to the submucous coat is the 
muscular coat, composed of two layers, one of circular 
fibers, the other of longitudinal fibers. An additional layer 
of oblique fibers is present in the cardiac end of the stom- 
ach, which aid in giving that organ the peculiar churning or 
peristaltic motion necessary for chymification of the food. 
A fourth coat or serous covering surrounds the muscular 
coat of the stomach and intestines. It is merely a reflected 
portion of the peritoneum which lines the entire abdominal 
cavity. 
THE ACCESSORY GLANDS OF DIGESTION. 
The salivary glands are five in number on each side of 
the head. They secrete the saliva, certain elements of 
which have the power of changing starch into sugar. 
The parotid gland is the largest of the salivary group 
and lies just ventrad to the base of the external ear (Fig. 
66) beneath the skin. It is flat and about two centimeters 
in diameter. Its secretion is poured into the mouth through 
Stenson’s duct, which may be seen extending from the 
cranial margin of the gland over the masseter muscle, to 
near the angle of the mouth, where it perforates the bucci- 
nator muscle, and opens within the mouth on the cheek, 
opposite the prominent cusp of the last premolar. The 
duct and gland may be injected with Berlin blue by insert- 
ing the cannula into the orifice of the duct (Fig. 66). 
The submaxillary gland is near the angle of the man- 
dible and ventrad to the parotid. Wharton’s duct extends 
from its anterior surface, between the digastric and masse- 
ter muscles, to its orifice on the floor of the mouth, opposite 
the last tooth of the mandible. 
The sublingual gland is quite small, elongated, and lies 
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