PRACTICAL QUESTIONS.--=1.= Can we always control the voluntary muscles? Do we shiver with the voluntary or involuntary muscles? =2.= If a man had absolute control over his muscles of respiration, what might he do that he cannot now do? =3.= Why is one who uses alcoholic drinks not likely to be a good marksman? =4.= Why should a youth who wishes to excel in athletic contests abstain from the use of tobacco? =5.= Is there any relation between the amount of bodily exertion necessary for a person’s health and the amount of wealth or the amount of intelligence he possesses? =6.= Can you relax the chewing muscles so that the lower jaw will swing loosely when the head is shaken? Can you relax your arm so that it falls like a rope if another person raises it and lets it fall? =7.= The average man has sixty pounds of muscle and two pounds of brain; one half of the blood goes through the muscles and less than one fifth goes through the brain. What inference may you draw as to the kind of life we should lead? =8.= Why is a slow walk of little value as exercise? =9.= How can we best prove that we have admiration and respect for our wonderful bodies? =10.= Why is the ability to relax the muscles thoroughly of great benefit to the health? How is this ability tested? (Question 6.) =11.= Why is it as correct to say that the muscles support the skeleton as the reverse? [Illustration: COLORED FIGURE 5. DIAGRAM OF CIRCULATION. 1. Head arteries (carotid). 2. Nameless arteries (innominate). 3. Collar bone (subclavian) artery. 4. Great bend of the aorta. 5. Pulmonary arteries. 6. Thoracic aorta. 7, 10. Abdominal aorta. 8. Artery to liver (hepatic). 9. Artery to spleen (splenic). 11. Artery to intestine (mesenteric). 12. Artery to kidney (renal). 13. Descending vena cava. 14. Nameless vein (innominate, 15 and 16 before branching). 15. Collar bone vein (subclavian). 16. Jugular vein. 17. Pulmonary vein. 18. Ascending vena cava. 19. Vein from liver (hepatic). 20. Vein from stomach (gastric). 21. Vein from spleen. 22. Vein from intestine. 23. Vein to liver (portal). 24. Vein from kidney. 25. Right auricle. 26. Left auricle. 27. Right ventricle. 28. Left ventricle. 29. Thoracic duct. 30. Stomach. 31. Spleen. 32. Liver. 33. Kidneys. 34. Duodenum. 35. Ascending colon. 36. Descending colon. 37. Lymphatic glands of mesentery.] CHAPTER V THE CIRCULATION _Experiment 1._ =Anatomy of Mammalian Heart.=--Get a sheep’s or beef’s heart from the butcher. Get the whole heart, not simply the ventricles (as usually sold). Note the blood vessels, four chambers, thickness of different walls, valves, cords, openings.