Observation shows, that disease, habit, the state of the mind, and other circ.u.mstances, exert an influence on the appet.i.te.

284. Show the effect of habit upon the quant.i.ty of food that is eaten.

What is said in regard to inordinate eating? 285. What is the effect of eating large quant.i.ties 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 a.s.sertion of some persons relative to the quant.i.ty of food necessary for the system?

_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 circ.u.mstances. 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 same individual in all conditions; as vocation, health, exposure, habits of life, season, climate, &c., influence the condition of the system.

What does observation show? 288. What is said of the causes of hunger? 289. Why is not the same kind of food adapted to different individuals?

290. All articles of food may be considered in two relations: 1st, As nutritive. 2d, As digestible. Substances are nutritious in proportion to their capacity to yield the elements of chyle, of which carbon, oxygen, hydrogen, and nitrogen are the most essential; they are digestible in proportion to the facility with which they are acted upon by the gastric juice. These properties should not be confounded in the various articles used for food.

291. As a "living body has no power of forming elements, or of converting one elementary substance into another, it therefore follows that the elements of which the body of an animal is composed must be in the food." (Chap. III.) Of the essential const.i.tuents of the human body, carbon, hydrogen, oxygen, and nitrogen are the most important, because they compose the princ.i.p.al part of the animal body; while the other elements are found in very small proportions, and many of them only in a few organs of the system. (Appendix G.)

_Observation._ Nitrogen renders food more stimulating, particularly if combined with a large quant.i.ty of carbon, as beef. Those articles that contain the greatest amount of the const.i.tuent elements of the system are most nutritious. As milk and eggs contain all the essential elements of the human system, so they are adapted to almost universal use, and are highly nutritious.

290. In what proportion are substances nutritious? Digestible? Why does beef stimulate the system? What is said of milk and eggs?

292. The following table, by Pereira, in his treatise on Food and Diet may aid the student in approximating to correct conclusions of the quant.i.ty of nutriment in different kinds of food, and its adaptation to the wants of the system.

TABLE,

SHOWING THE AVERAGE QUANt.i.tY OF DRY, OR SOLID MATTER, CARBON, NITROGEN, AND MOISTURE, IN DIFFERENT ARTICLES OF DIET.

-------------------+---------+---------+-----------+------------ One hundred Parts.

Dry

Carbon.

Nitrogen.

Water

Matter.

-------------------+---------+---------+-----------+------------ Arrowroot,

81.8

36.4

18.2 Beans,

85.89

38.24

14.11 Beef, fresh,

25

12.957

3.752

75 Bread, rye,

67.79

30.674

32.21 b.u.t.ter,

100

65.6

Cabbage,

7.7

0.28

92.3 Carrot,

12.4

0.30

87.6 Cherries,

25.15

74.85 Chickens,

22.7

77.3 Codfish,

20

80 Cuc.u.mbers,

2.86

97.14 Eggs, whites,

20

80 ----, yolk,

46.23

53.77 Lard, hog's,

100

79.098

Milk, cow's,

12.98

87.02 Oats,

79.2

40.154

1.742

20.8 Oatmeal,

93.4

6.6 Olive-oil,

100

77.50

Oysters,

12.6

87.4 Peaches,

19.76

80.24 Pears,

16.12

83.88 Peas,

84

35.743

16 Plums, greengage,

28.90

71.10 Potatoes,

24.1

10.604

0.3615

75.9 Rye,

83.4

38.530

1.417

16.6 Suet, mutton,

100

78.996

Starch, potato,

82

36.44

18 ----, wheat,

85.2

37.5

14.8 Sugar, maple,

42.1

----, refined,

42.5

----, brown,

40.88

Turnips,

7.5

3.2175

0.1275

92.5 Veal, roasted,

52.52

14.70

Wheat,

85.5

39.415

1.966

14.5 -------------------+---------+---------+-----------+------------

_Note._ Let the pupil mention those articles of food that are most nutritious, from a review of this table, and the last four paragraphs.

293. Those articles that do not contain the essential elements of the system should not be used as exclusive articles of diet. This principle has been, and may be ill.u.s.trated by experiment. Feed a dog with pure sugar, or olive-oil, (articles that contain no nitrogen,) for several weeks, and the evil effects of non-nitrogenous nutriment will be manifested. At first, the dog will take his food with avidity, and seem to thrive upon it; soon this desire for food will diminish, his body emaciate, his eye become ulcerated, and in a few weeks he will die; but mix bran or sawdust with the sugar or oil, and the health and vigor of the animal will be maintained for months. A similar phenomenon will be manifested, if grain only be given to a horse, without hay, straw, or material of like character. (Appendix H.)

294. Some articles of food contain the elements of chyle in great abundance, yet afford but little nutriment, because they are difficult of digestion; while other articles contain but a small quant.i.ty of these elements, and afford more nourishment, because they are more easily affected by the digestive process.

293. How has the effect of non-nitrogenous nutriment been ill.u.s.trated?

294. Why do some articles of food that contain the elements of chyle afford but little nutriment? Why do articles that contain a small quant.i.ty of these elements afford more nourishment? 295. How was the time required for digesting different articles of food ascertained?

295. The following table exhibits the general results of experiments made on Alexis St. Martin, by Dr. Beaumont, when he endeavored to ascertain the time required for the digestion of different articles of food.[10] The stomach of St. Martin was ruptured by the bursting of a gun. When he recovered from the effects of the accident under the surgical care of Dr. Beaumont, the stomach became adherent to the side, with an external aperture. Nature had formed a kind of valve, which closed the aperture from the interior, and thus prevented the contents of the stomach from escaping; but on pushing it aside, the process of digestion could be seen. Through this opening, the appearance of the coats of the stomach and food, at different stages of digestion, were examined.

[10] The time required for the digestion of the different articles of food might vary in other persons; and would probably vary in the same individual at different periods, as the employment, health, season, &c., exert a modifying influence.

TABLE,

SHOWING THE MEAN TIME OF DIGESTION OF THE DIFFERENT ARTICLES OF DIET.

-----------------------------+--------------+-------- Articles.

Preparation.

Time

h. m.

-----------------------------+--------------+-------- Apples, sour, hard,

Raw,

2 50 Apples, sour, mellow,

Raw,

2 Apples, sweet, do.,

Raw,

1 30 Ba.s.s, striped, fresh,

Broiled,

3 Beans, pod,

Boiled,

2 30 Beef, fresh, lean, rare,

Roasted,

3 Beef, fresh, lean, dry,

Roasted,

3 30 Beef steak,

Broiled,

3 Beef, with salt only,

Boiled,

3 36 Beef, with mustard,

Boiled,

3 10 Beef, fresh, lean,

Fried,

4 Beef, old, hard, salted,

Boiled,

4 15 Beets,

Boiled,

3 45 Bread, wheat, fresh,

Baked,

3 30 Bread, corn,

Baked,

3 15 b.u.t.ter,

Melted,

3 30 Cabbage head,

Raw,

2 30 Cabbage, with vinegar,

Raw,

2 Cabbage,

Boiled,

4 30 Cake, sponge,

Baked,

2 30 Carrot, orange,

Boiled,

3 15 Catfish,

Fried,

3 30 Cheese, old, strong,

Raw,

3 30 Chicken, full-grown,

Fricas'd,

2 45 Codfish, cured, dry,

Boiled,

2 Corn, green, & beans,

Boiled,

3 45 Corn bread,

Baked,

3 15 Corn cake,

Baked,

3 Custard,

Baked,

2 45 Dumpling, apple,

Boiled,

3 Ducks, domesticated,

Roasted,

4 Ducks, wild,

Roasted,

4 30 Eggs, fresh,

Boiled hard,

3 30 Eggs, fresh,

Boiled soft,

3 Eggs, fresh,

Fried,

3 30 Eggs, fresh,

Raw,

2 Flounder, fresh,

Fried,

3 30 Fowl, domestic,

Boiled,

4 Fowl, domestic,

Roasted,

4 Goose,

Roasted,

2 30 Lamb, fresh,

Broiled,

2 30 Liver, beef's, fresh,

Broiled,

2 Meat hashed with vegetables,

Warm'd,

2 30 Milk,

Boiled,

2 Milk,

Raw,

2 15 Mutton, fresh,

Roasted,

3 15 Mutton, fresh,

Broiled,

3 Mutton, fresh,

Boiled,

3 Oysters, fresh,

Raw,

2 55 Oysters, fresh,

Roasted,

3 15 Oysters, fresh,

Stewed,

3 30 Parsnips,

Boiled,

2 30 Pig, sucking,

Roasted,

2 30 Pigs' feet, soused,

Boiled,

1 Pork, fat and lean,

Roasted,

5 15 Pork, recently salted,

Boiled,

4 30 Pork, recently salted,

Fried,

4 15 Pork, recently salted,

Broiled,

3 15 Pork, recently salted,

Raw,

3 Pork, steak,

Broiled,

3 15 Potatoes, Irish,

Boiled,

3 30 Potatoes, Irish,

Baked,

2 30 Rice,

Boiled,

1 Sago,

Boiled,

1 45 Salmon, salted,

Boiled,

4 Sausage, fresh,

Broiled,

3 20 Soup, beef, vegetables, and

Boiled,

4 bread,

Soup, chicken,

Boiled,

3 Soup, mutton,

Boiled,

3 30 Soup, oyster,

Boiled,

3 30 Suet, beef, fresh,

Boiled,

5 30 Suet, mutton,

Boiled,

4 30 Tapioca,

Boiled,

2 Tripe, soused,

Boiled,

1 Trout, salmon, fresh,

Boiled,

1 30 Trout, salmon, fresh,

Fried,

1 30 Turkey, domesticated,

Roasted,

2 30 Turkey,

Boiled,

2 25 Turkey, wild,

Roasted,

2 18 Turnips, flat,

Boiled,

3 30 Veal, fresh,

Broiled,

4 Veal, fresh,

Fried,

4 30 Venison steak,

Broiled,

1 35 -----------------------------+--------------+--------

296. In view of this table, the question may be suggested, Is that article of food most appropriate to the system which is most easily and speedily digested? To this it may be replied, that the stomach is subject to the same law as the muscles and other organs; exercise, within certain limits, strengthens it. If, therefore, we always eat those articles most easily digested, the digestive powers will be weakened; if over-worked, they will be exhausted. Hence the kind and amount of food should be adapted to the maintenance of the digestive powers, and to their gradual invigoration when debilitated.

_Observation._ Food that is most easily digested is not always most appropriate to a person convalescing from disease. If the substance pa.s.ses rapidly through the digestive process, it may induce a recurrence of the disease. Thus the simple preparations which are not stimulating, as water-gruel, are better for a sick person than the more digestible beef and fish.

297. The question is not well settled, whether animal or vegetable food is best adapted to nourish man. There are nations, particularly in the torrid zone, that subsist, exclusively, on vegetables; while those of the frigid zone feed on fish or animal food. In the temperate zone, among civilized nations, a mixed diet is almost universal. When we consider the organization of the human system, the form and arrangement of the teeth, the structure of the stomach and intestines, we are led to conclude, that both animal and vegetable food is requisite, and that a mixed diet is most conducive to strength, health, and long life.

296. How is the question answered, whether that article is most appropriate to the system which is most easily digested? Give observation. 297. What is said of the adaptation of animal and vegetable food to man?

298. _The food should be adapted to the distensible character of the stomach and alimentary ca.n.a.l._ The former will be full, if it contain only a gill; it may be so distended as to contain a quart. The same is true of the intestines. If the food is concentrated, or contains the quant.i.ty of nutriment which the system requires, in small bulk, the stomach and intestines will need the stimulation of distention and friction, which is consequent upon the introduction and transit of the innutritious material into and through the alimentary ca.n.a.l. If the food is deficient in innutritious matter, the tendency is, to produce an inactive and diseased condition of the digestive organs. For this reason, nutrient food should have blended with it innutritious material. Unbolted wheat bread is more healthy than hot flour cakes; ripe fruits and vegetables than rich pies, or jellies.

_Observation._ 1st. The observance of this rule is of more importance to students, sedentary mechanics, and those individuals whose digestive apparatus has been enfeebled, than to those of active habits and firm health.

2d. The circ.u.mstance that different articles of food contain different proportions of waste, or innutritious matter, may be made practically subservient in the following way: If, at any particular season of the year, there is a tendency to a diarrhoea, an article that contains a small proportion of waste should be selected for food; but, if there is a tendency to an inactive or costive condition of the intestinal ca.n.a.l, such kinds of food should be used as contain the greatest proportion of waste, as such articles are most stimulating to the digestive organs, and, consequently, most laxative.

299. _In the selection of food, the influence of season and climate should be considered._ Food of a highly stimulating character may be used almost with impunity during the cold weather of a cold climate; but in the warm season, and in a warm climate, it would be very deleterious. Animal food, being more stimulating than vegetable, can be eaten in the winter but vegetable food should be used more freely in the spring and summer.

298. What is said of the distensible character of the stomach and alimentary ca.n.a.l? What is the effect of eating highly concentrated food? Why is the unbolted wheat bread more healthy than flour cakes?

Give observation 1st. Observation 2d. 299. What kind of food is adapted to cold weather? To warm weather?

300. _The influence of food on the system is modified by the age of the individual._ The organs of a child are more sensitive and excitable than those of a person advanced in years. Therefore a vegetable diet would be most appropriate for a child, while stimulating animal food might be conducive to the health of a person advanced in life.

_Observation._ When the digestive organs are highly impressible or diseased, it is very important to adopt a nutritious, unstimulating, vegetable diet, as soon as the warm season commences.

301. _Habit is another strong modifying influence._ If a person has been accustomed to an animal or vegetable diet, and there is a sudden change from one to the other, a diseased condition of the system, particularly of the digestive apparatus, usually follows. When it is necessary to change our manner of living, it should be done gradually.[11]