Different theories of Digestion--Concoction--Fermentation --Putrefaction--Trituration--Chemical solution--Conditions or laws of digestion--Influence of gastric juice.--Experiments illustrative of its solvent power--Its mode of action on different kinds of aliment--beef, milk, eggs, soups, &c.--Influence of temperature--Heat of about 100° essential to digestion.--Gentle and continued agitation necessary--Action of stomach in admitting food--Uses of its muscular motion--Gastric juice acts not only on the surface of the mass, but on every particle which it touches--Digestibility of different kinds of food--Table of results--Animal food most digestible--Farinaceous next--Vegetables and soups least digestible--Organs of digestion simple in proportion to concentration of nutriment--Digestibility depends on adaptation of food to gastric juice more than on analogy of composition--Illustrations.--No increase of temperature during digestion--Dr Beaumont’s summary of inferences, 109–151 CHAPTER VI. CHYLIFICATION, AND THE ORGANS CONCERNED IN IT. Chylification--Not well known--Organs concerned in it--The intestinal canal--Its general structure--Peritoneal coat--Mesentery--Muscular coat--Uses of these--Air in intestines--Uses of--Mucous coat--Analogous to skin--The seat of excretion and absorption--Mucous glands--Absorbent vessels--Course of chyle towards the heart--Nerves of mucous coat--Action of bowels explained--Individual structure of intestines--The Duodenum--Jejunum--and Ileum--Liver and pancreas concerned in chylification--Their situation and uses--Bile, its origin and uses--The pancreas--Its juice--The jejunum described--The ileum--Cœcum--Colon--and Rectum--Peristaltic motion of bowels--Aids to it--Digestion of vegetables begins in stomach but often finished in the bowels--Illustration from the horse--Confirmation by Dupuytren, 152–183 PART II. THE PRINCIPLES OF DIETETICS VIEWED IN RELATION TO THE LAWS OF DIGESTION. CHAPTER I. TIMES OF EATING.