n is not correct, as an
appetite may be created for food by condiments and gormandizing, which
is as artificial and as morbid as that which craves tobacco or ardent
spirits. On the other hand, a structural or functional disease of the
brain may prevent that organ from taking cognizance of the sensations
of the stomach, when the system actually requires nourishment.
Observation shows, that disease, habit, the state of the mind, and
other circumstances, exert an influence on the appetite.

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284. Show the effect of habit upon the quantity of food that is eaten.
What is said in regard to inordinate eating? 285. What is the effect
of eating large quantities of food? What suggestion when an
extraordinary effort, either mental or physical, is to be made? 286.
How much food should generally be eaten? 287. What is the assertion of
some persons relative to the quantity of food necessary for the
system?

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_Observation._ Dr. Beaumont noticed, in the experiments upon Alexis
St. Martin, that after a certain amount of food was converted into
chyme, the gastric juice ceased to ooze from the coats of the stomach.
Consequently, it has been inferred by some writers on physiology, that
the glands which supply the gastric fluid, by a species of instinctive
intelligence, would only secrete enough fluid to convert into chyme
the aliment needed to supply the real wants of the system. What are
the reasons for this inference? There is no evidence that the gastric
glands possess instinctive intelligence, and can there be a reason
adduced, why they may not be stimulated to extra functional action as
well as other organs, and why they may not also be influenced by
habit?

288. While all agree that the remote or predisposing cause of hunger
is, usually, a demand of the system for nutrient material, the
proximate or immediate cause of the sensation of hunger is not clearly
understood. Some physiologists suppose that it is produced by an
engorged condition of the glands of the stomach which supply the
gastric juice; while others maintain that it depends on a peculiar
condition of the nervous system.

289. The QUALITY of the food best adapted to the wants of the system
is modified by many circumstances. There are many varieties of food,
and these are much modified by the different methods of preparation.
The same kind of food is not equally well adapted to different
individuals, or to the s