I? 2 AtfSWEXS TO PRACTICAL QUESTIONS 



28. How is the heart itself nourished ? 



The coronary arteries springing from the aorta just 

 after its origin, carry blood to the muscular walls of the 

 heart : the venous blood comes back through the coronary 

 veins, and empties directly into the right auricle. 



29. Does any venous blood reach the heart without com- 

 Ing through the vena cavcz ? 



(See Question 28.) 



155. i. How do clothing and shelter economize food ? 



The force which would be converted into heat to pre- 

 serve the temperature of the body, is saved. The food 

 needed to supply this amount of force may be reserved 

 or changed into flesh, or into other forms of force. 



2. Is it well to take a long walk before breakfast ? 



(See Physiology, page 53.) 



A vigorous person in good health and in a healthy 

 region may do so, but one in ill health, or a malarious 

 district, needs to be braced with food before taking any 

 except very light exercise. 



3. Why is warm food easier to digest than cold? 



Heat favors the chemical change whereby the food is 

 prepared for assimilation. 



4. Why is salt beef less nutritious than fresh ? 



(See Physiology, page 155, note.) 



The salts and juices of the meat are extracted by the 

 brine. 



