21. “ The Blood in the Capillaries 40 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 47. “ The Mucous Membrane of the Alimentary Canal and its Glands 109 48. “ The Salivary Glands, Pancreas and Liver 111 49. “ Food-stuffs 113 50. “ How proteids and starch are changed 115 51. “ Lacteals and Lymphatics 117 52. “ What becomes of the Food-stuffs 120 VIII. HOW THE BLOOD GETS RID OF WASTE MATTERS. 53. “ The need of getting rid of Waste Matters 123 54. “ The Kidneys get rid of Ammonia in the form of Urea 125