THE STOMACH 355 



9. Why does your head nod when you doze in your chair? 



10. Do you think you are taller at night, or in the morning? Meas- 

 ure yourself, and explain what you find out. 



1 1 . Give the reasons why sleep rests the body. 



12. We are told that milk, and cereals such as oatmeal, are good for 

 young children, because they assist in bone making. What nutrients 

 must they supply? 



13. Why do stones, sand, glass, etc., have no taste? 



14. Why is the tongue provided with nerves of touch? 



15. Why should a child's first teeth be cared for, even though they 

 are soon to be replaced by the permanent set? Why ought we to be 

 careful about bringing cold food, such as iced water, ice cream, and 

 cold melons, in contact with the teeth? 



16. Why is milk sometimes called a "perfect" food? 



17. Yeast contains the ferment invertase, which changes cane 

 sugar into grape sugar and fruit sugar (cf. 357). It also contains 

 zymase. How does this change the grape and fruit sugars? (Cf. 

 129.) 



363. The Stomach. As we learned in 361, the 

 esophagus lies against the backbone, and passes through 

 the thorax into the abdomen. The stomach, at the 

 lower end of the esophagus, is wholly within the abdomen, 

 on the left side, and partly under the ribs. It is about 

 a foot long and about 4 inches in diameter. The stomach 

 is really an expansion of the digestive tract, like a lake 

 formed by the widening of a river. There is nothing to 

 close the entrance from the esophagus into the stomach, 

 but the opening (pylorus) from the stomach into the small 

 intestine is closed by a muscular ring while digestion is 

 going on in the stomach. 



The method by which food is carried down the esopha- 

 gus has been partly explained in 361: the circular 

 muscles contract above the food. The esophagus is also 



