Chapter V: Theory and Laws of Digestion

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.

The selection of food only one element in sound
digestion--Other conditions essential--Times of eating--No
stated hours for eating--Five or six hours of interval
between meals generally sufficient--But must vary according
to circumstances--Habit has much influence--Proper time
for breakfast depends on constitution, health, and mode of
life--Interval required between breakfast and dinner--Best
time for dinner--Circumstances in which lunch is
proper--Late dinners considered--Their propriety dependent
on mode of life--Tea and coffee as a third meal, useful
in certain circumstances--Supper considered--General rule
as to meals--Nature admits of variety--illustrations--but
requires the observance of principle in our rules, 187–217

CHAPTER II.

ON THE PROPER QUANTITY OF FOOD.

Quantity to be proportioned to the wants of the
system--Appetite indicates these--Cautions in trusting to
appetite--General error in eating too much--Illustrations
from Beaumont, Caldwell, Head, and Abercrombie--Mixtures
of food hurtful chiefly as tempting to excess in
quantity--Examples of disease from excess in servant-girls
from the country, dressmakers, &c.--Mischief from excessive
feeding in infancy--Rules for preventing this--Remarks on
the consequences of excess in grown persons--Causes of
confined bowels explained--And necessity of fulfilling the
laws which God has appointed for the regulation of the
animal economy inculcated, 218–250

CHAPTER III.

OF THE KINDS OF FOOD.

What is the proper food of man?--Food to be adapted
to constitution and circumstances--Diet must vary
with time of life--Diet in infancy--The mother’s
milk the best--Substitutes for it--Over-feeding a
prevalent error--Causes which vitiate the quality
of the milk--Regimen of nurses--Weaning--Diet after
weaning--Too early use of animal food hurtful--Diet of
children in the higher classes too exciting--and produces
scrofula--Mild food best for children--Incessant eating
very injurious--Proper diet from childhood to puberty--It
ought to be full and nourishing but not stimulating--Often
insufficient in boarding-schools--Diet best adapted
for different constitutions in mature age--Regimen
powerful in modifying the constitution, mental as well as
physical--Farther investigation required, 251–287

CHAPTER IV.

CONDITIONS TO BE OBSERVED BEFORE AND AFTER EATING.

General laws of organic activity apply to the stomach as
well as to other parts--Increased flow of blood towards
the stomach during digestion--Hence less circulating in
other organs--and consequently less aptitude for exertion
in them--Bodily rest and mental tranquillity essential
to sound digestion--Rest always attended to before
feeding horses--Hence also a natural aversion to exertion
immediately after eating--Mischief done by hurrying away
to business after meals--Severe thinking hurtful at that
time--Playful cheerfulness after dinner conducive to
digestion--The mind often the cause of indigestion--Its
mode of operation explained--Also influences
nutrition--Illustration from Shakspeare--Importance of
attending to this condition of health enforced, 288–303

CHAPTER V.

ON DRINKS.

Thirst the best guide in taking simple drinks--Thirst
increased by diminution of the circulating fluids--The
desire for liquids generally an indication of their
propriety--Much fluid hurtful at meals--Most useful three
or four hours later--The temperature of drinks is of
consequence--Curious fall of temperature in the stomach
from cold water--Ices hurtful after dinner--Useful in
warm weather, when digestion is completed and caution
used--Cold water more dangerous than ice when the body
is overheated--Tepid drinks safest and most refreshing
after perspiration--Kinds of drink--Water safe for every
constitution--Wine, spirits, and other fermented liquors,
too stimulating for general use, but beneficial in certain
circumstances--Test of their utility, 304–323