153. How is this force set free? What force is this? How can it be turned into muscular motion, mental vigor, etc.? Do we then draw all our power from nature? What becomes of these forces when we are done with them? Do we destroy the force we use? Ans. No matter has been destroyed, so far as we know, since the creation, and force is equally indestructible. Compare our food to a tense spring.
154. What three kinds of food do we need? What is nitrogenous food? Name the common forms. What is the characteristic of nitrogenous food? Why called albuminous? What is carbonaceous food? Its two kinds? Constituents of sugar? Where are starch and gum ranked? Why? Use of carbonaceous food? What becomes of this heat? Composition of fat? How does fat compare with sugar in producing heat?
155. Name the other uses of carbonaceous food. From what kind of food does the body derive the greatest strength? Name the mineral matters which should be contained in our food. What can you say of the abundance and necessity of water? Ought we not to exercise great care in selecting the water we drink? [Footnote: Water which has passed through lead pipes is apt to contain salts of that metal, and is therefore open to suspicion. Metallic lined ice pitchers, galvanized-iron reservoirs, and many soda- water fountains, are liable to the same objection. (See pp. 317, 318.)] Does the character of our food influence the quantity of water we need?
156. What are the uses of the different minerals contained in food? Illustrate the importance of salt. Could a person live on one kind of food alone? Illustrate.
157. Describe the effect of living on lean meat. Show the necessity of a mixed diet. Illustrate. Show the need of digestion. Illustrate.
158. What is assimilation? Describe the general plan of digestion. What did Berzelius call digestion? Why? What amount of liquid is daily secreted by the alimentary canal? What is the alimentary canal? How is it lined? How does the amba digest its food?
159. The hydra? Define secretion. Describe the saliva. How is it secreted? What is the amount? Its organic principle? Its use? How soon does it act? How long? What tends to check or increase the flow of saliva?
160. Describe the process of swallowing. The stomach. Its size. Its construction. What is the peristaltic movement?
162. What is the pylorus? For what does this open? What is the gastric juice? How abundant is it? To what is its acidity due? What organic principle does it contain? How is pepsin prepared? How is the flow of gastric juice influenced?
163. What is its use? Appearance of the food as it passes through the pylorus? Why is not the stomach itself digested? What is the construction of the intestines? How are the intestines divided? What is the duodenum? Why so called? What juices are secreted here?