_The Principal Processes of Nutrition--The General Plan of Digestion-- Mastication--The Teeth--Preservation of the Teeth--Insalivation--The Stomach and the Gastric Juice--The Movements of the Stomach--Gastric Digestion--The Intestines--The Bile and Pancreatic Juice--Intestinal Digestion--Absorption by means of Blood-vessels and Lacteals--The Lymphatic or Absorbent System--The Lymph--Conditions which affect Digestion--The Quality, Quantity, and Temperature of the Food--The Influence of Exercise and Sleep._ CHAPTER VII. THE CIRCULATION 101 _The Blood--Its Plasma and Corpuscles--Coagulation of the Blood--The Uses of the Blood--Transfusion--Change of Color--The Organs of the Circulation--The Heart, Arteries, and Veins--The Cavities and Valves of the Heart--Its Vital Energy--Passage of the Blood through the Heart--The Frequency and Activity of its Movements--The Pulse--The Sphygmograph--The Capillary Blood-vessels--The Rate of the Circulation--Assimilation--Injuries to the Blood-vessels._ CHAPTER VIII. RESPIRATION 123 _The Objects of Respiration--The Lungs--The Air-Passages--The Movements of Respiration--Expiration and Inspiration--The Frequency of Respiration--Capacity of the Lungs--The Air we Breathe--Changes in the Air from Respiration--Changes in the Blood--Interchange of Gases in the Lungs--Comparison between Arterial and {7} Venous Blood--Respiratory Labor--Impurities of the Air--Dust--Carbonic Acid--Effects of Impure Air--Nature's Provision for Purifying the Air--Ventilation--Animal Heat_. CHAPTER IX. THE NERVOUS SYSTEM 148 _Animal and Vegetative Functions--Sensation, Motion, and Volition--The Structure of the Nervous System--The White and Gray Substances--The Brain--Its Convolutions--Cerebellum--The Spinal Cord and its System of Nerves--The Anterior and Posterior Roots--The Sympathetic System of Nerves--The Properties of Nervous Tissue--Excitability of Nervous Tissues--The Functions of the Spinal Nerves and Cord--The Direction of the Fibres of the Cord--Reflex Activity and its Uses--The Functions of the Medulla Oblongata and the Cranial Ganglia--The Reflex Action of the Brain._ CHAPTER X. THE SPECIAL SENSES 177