

CHAPTER VII 



THE MOUTH SWALLOWING; SALIVARY 

 DIGESTION 



Mastication. The hygienic importance of thorough 

 mastication is undoubted, but there is little occasion for 



ly extended analysis of a process so obvious. It is to be 

 observed that the lower jaw does not have merely an up- 

 and-down movement, but that it glides backward and 

 forward and has some lateral play at the same time. The 

 teeth, therefore, do not simply chop the food, but rub and 

 grind it. In the work of mechanical reduction a larger 

 part is borne by the tongue than is commonly recognized. 

 The little member seems to be everywhere at once, thrust- 

 ing food between the teeth, withdrawing it again, bruising 

 and rasping it against the roof of the mouth. While this 



ion is going on an intimate mixture with the saliva 

 is accomplished. We must now proceed to a discussion 

 of this the first of the digestive secretions. 



Mention has been made of the three pairs of glands which 

 supply the saliva. Their united product is estimated to 

 reach an amount of about 3 pints a day, equalling the vol- 

 ume of the urine. If one finds it hard to credit such a 

 statement, attention may be called to the copious character 

 of the flow which is noted when one is interrupted at the 

 moment of taking food. There is little secretion apart 

 from eating unless it is excited by chewing sundry things. 



(At mealtime a large part of what is swallowed is saliva, 

 and the proportion must be greatly raised by the practice 

 of prolonged mastication, so-called Fletcherism. The 

 formation of saliva is to be regarded as a reflex in which 

 the primary stimulation is furnished by food in the mouth 



