Part 3

22. “ The Corpuscles of the Blood 42

23. “ The clotting of Blood 45

24. “ The substances present in Serum 48

25. “ The minerals in Blood 50

V. HOW THE BLOOD MOVES.

26. “ The Arteries, Capillaries, and Veins 51

27. “ The Sheep’s Heart 55

28. “ The Course of the Circulation 58

29. “ Why the blood moves in one direction only; the Valves of the Veins 64

30. “ The Tricuspid Valves of the Heart 66

31. “ The pulmonary Semilunar Valves 71

32. “ The left side of the Heart 72

33. “ What makes the blood move at all: The beat of the Heart 76

34. “ The action of the Heart as a whole 79

35. “ The Capillaries and the Tissues 82

VI. HOW THE BLOOD IS CHANGED BY AIR: BREATHING.

36. “ Venous and Arterial Blood 85

37. “ The change from Arterial to Venous, and from Venous to Arterial Blood 87

38. “ The Lungs 88

39. “ The renewal of Air in the Lungs. How the descent of the Diaphragm expands the Lungs 90

40. “ The natural distension of the Lungs. Inspiration. Expiration 91

41. “ How the Diaphragm descends 96

42. “ The Chest is also enlarged by the movements of the Ribs and Sternum 98

43. “ Breathing an involuntary act 100

44. “ Tidal air; stationary air 101

VII. HOW THE BLOOD IS CHANGED BY FOOD: DIGESTION.

45. “ Why the inside of the mouth is always red and moist 103

46. “ Why the Skin is sometimes moist. Sweat Glands 106