CHAPTER XX. 



NUTRITIVE FUNCTIONS. DIGESTION. 



1. (j)igestion, absorption, secretion, and nutrition constitute 

 what are called the nutritive functions.} Digestion is that 

 process by which the food is brought into a state in which 

 it may be taken up by the lacteal vessels and carried into 

 the blood. (.The digestive apparatus consists of the mouth 

 and its appendages ; the pharynx ; esophagus ; the stomach 

 and intestines^ the whole tract making what is called the 

 alimentary canal. Besides these, there are the salivary 

 glands ; the liver ; the pancreas, or sweet-bread of animals ; 

 all of which aid in the process of digestion. 



2. The parts which compose the mouth, are (the lips, 

 cheeks, palate, tongue, teeth, and salivary glands} There are 

 six salivary glands, which secrete saliva, viz.: the parotid; 

 sub-maxillary ; and the sub-lingual. The parotid gland is 

 situated on the cheek before the ear ; the sub-maxillary im- 

 mediately beneath the lower jaw ; and the sub-lingual under 

 the tongue. They all pour forth a fluid, during mastication, 

 into the mouth to moisten the food, and prepare it for the 

 change it is to undergo in the stomach. A swelling of the 

 parotid gland is called the mumps. 



3. In a grown person, there are thirty-two teeth ; four in- 

 cisor, or cutting teeth, two canine or dog teeth, ten molar or 

 grinders in each jaw. The first set of teeth begin to come, 

 when the child is about six months old, and by the time it is 

 two years and a half old, it has twenty ; about the seventh 

 year, they all become loose and fall out, and their place is 

 supplied by another set. The teeth are the hardest part of 

 the body ; their internal parts resemble bone ; the external 

 consist of a very hard and highly polished substance, called 

 enamel t which is very durable. 



