TABLE OF CONTENTS, 



vu 



36. 



37- 



38- 

 39- 



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III. It is the food in the blood which gives the 



muscle strength yj 



The continual need of food . . . . 38 



VI. 



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THE NATURE OF BLOOD. 



The Blood in the Capillaries 

 The Corpuscles of the Blood 

 The clotting of Blood . 

 The substances present in Serum 

 The minerals in Blood . 



HOW THE BLOOD MOVES. 



The Arteries, Capillaries, and Veins 

 The Sheep's Heart .... 

 The Course of the Circulation 

 Why the blood moves in one direction only 



the Valves of the Veins 

 The Tricuspid Valves of the Heart 

 The pulmonary Semilunar Valves 

 The left side of the Heart 

 What makes the blood nvove at all : The 



beat of the Heart .... 

 The action of the Heart as a whole 

 The Capillaries and the Tissues . 



HOW THE BLOOD IS CHANGED 

 BY AIR : BREATHING. 



Venous and Arterial Blood .... 



The change from Arterial to Venous, and 

 from Venous to Arterial Blood . 



The Lungs 



The renewal of Air in the Lungs. How the 

 descent of the Diaphragm expands the 

 Lungs 



40 



42 



45 

 48 



50 



51 



55 

 58 



64 

 66 



71 



72 



76 



79 

 82 



85 



87 

 88 



90 



