THE DIGESTION OF FOOD 127 



must be on our guard against certain things which may 

 injure the enamel. 



Picking the teeth with pins and needles is hurtful. We 

 should never crack nuts, crush hard candy, or bite off stout 

 thread with the teeth. The continued use of gritty and 

 cheap tooth powders, and very hot food and drink often 

 injure the enamel. 



The greatest care should be taken in saving the teeth. 

 The last resort of all is to lose a tooth by having it extracted. 

 A skilled dentist can save almost anything in the form of 

 a tooth. 



179. Effect of Alcohol upon Mucous Membranes. Alcohol 

 is a distinct irritant of the mucous membranes. Thus, when 

 raw spirit is taken into the mouth, it causes a burning 

 sensation. When diluted it does the same thing, but of 

 course in a less irritating way. By this irritation the epi- 

 thelial cells of the mucous membranes of the mouth, as 

 well as the salivary glands, secrete an unusual amount of 

 water. This gives rise to a sense of dryness and of thirst. 1 

 The mucous membrane of the stomach is irritated in a 

 similar way. 



180. General Effect of Alcohol on the Stomach. Alcohol 

 acts as a mild or powerful irritant of the stomach accord- 

 ing as it is taken diluted or strong. Its habitual use leads 

 to distressing forms of disease of the stomach. If we could 

 look into the stomach, as Dr. Beaumont looked into the 

 stomach of Alexis St. Martin, just after taking a drink of 

 raw spirit, we should find that the inner surface would be 



1 A noted French physiologist, M. Lancereaux, has found that the use 

 of alcoholic drinks produces a softening of the salivary glands, together 

 with other changes in the tissue composing them. This causes alterations 

 in the saliva itself and accounts for the dryness of the mouth so common 

 among persons addicted to the use of alcohol. 



