Chapter IX: Part 9

Slight curvature of the spine either backward or forward is helped most by exercises which tend to straighten the body, such as stretching up with the hands above the head. Lateral curvature of the spine, too often caused by a "hunched-up" position at the school desk, may also be corrected by exercises which tend to lengthen the spinal column.

It is the duty of every girl and boy to have good posture and erect carriage, not only because of the better state of health which comes with it, but also because one's self-respect demands that each one of us makes the best of the gifts that nature has given us. An erect head, straight shoulders, and elastic carriage go far toward making their owner both liked and respected.

Other Body Structures.--In spaces between the muscles are found various other structures,--blood vessels, which carry blood to and from the great pumping station, the heart, and thence to all parts of the body; connective tissue, which holds groups of muscle or other cells together; fat cells, scattered in various parts of the body; various gland cells, which manufacture enzymes; and the cells of the nervous system, which aid in directing the body parts.

Body Cavity.--Within the body is a cavity, which in life is almost completely filled with various organs. A thin wall of muscle called the _diaphragm_ divides the body cavity into two unequal spaces. In the upper space are found the _heart_ and _lungs_, in the lower, the digestive tract with its glands, the _liver_, _kidneys_, and other structures (see page 267).

Digestion, Absorption, and Excretion.--Running through the body is a food tube in which undigested food is placed and from which digested or liquid food is absorbed into the blood so that the cells of the various organs which do the work may receive food. Emptying into this food tube are various groups of gland cells, which pour digestive fluids over the solid foods, thus aiding in changing them to liquids. Solid wastes are passed out through the posterior end of the food tube, while liquid wastes are excreted by means of glands called _kidneys_.

Work done by Cells.--Food, prepared in the digestive tract, and oxygen from the lungs are taken by the blood to the cells. Bathed in liquid food, the cells do their work; they promote the oxidization of food and the exchange of carbon dioxide for oxygen in the blood, while other wastes of the cells are given off, to pass eventually through the kidneys and out of the body.

The Nervous System.--The smooth working of the bodily machine is due to another set of structures which direct the working of the parts so that they will act in unison. This director is the nervous system. We have seen that, in the simplest of animals, one cell performs the functions necessary to its existence. In the more complex animals, where groups of cells form tissues, each having a different function, a nervous system is developed. _The functions of the human nervous system are:_ (1) _the providing of man with sensation, by means of which he gets in touch with the world about him;_ (2) _the connecting of organs in different parts of the body so that they act as a united and harmonious whole;_ (3) _the giving to the human being a will, a provision for thought._ Cooperation in word and deed is the end attained. We are all familiar with examples of the cooperation of organs. You see food; the thought comes that it is good to eat; you reach out, take it, raise it to the mouth; the jaws move in response to your will; the food is chewed and swallowed. While digestion and absorption of the food are taking place, the nervous system is still in control. The nervous system also regulates pumping of blood over the body, respiration, secretion of glands, and, indeed, every bodily function. Man is the highest of all animals because of the extreme development of the nervous system. Man is the thinking animal, and as such is master of the earth.

REFERENCE READING FOR THIS AND SUCCEEDING CHAPTERS ON HUMAN BIOLOGY

ELEMENTARY

Hunter, _Laboratory Problems in Civic Biology_. American
Book Company.
Davison, _The Human Body and Health_. American Book Company.
Gulick, _The Gulick Hygiene Series_. Ginn and Company.
Overton, _General Hygiene_. American Book Company.
Ritchie, _Human Physiology_. World Book Company.
Sharpe, _Laboratory Manual in Botany_, pages 218-225.
American Book Company.

ADVANCED

Halliburton, _Kirk's Handbook of Physiology_. P. Blakiston's
Son and Company.
Hough and Sedgwick, _The Human Mechanism_. Ginn and Company.
Howell, _Physiology_, 3d edition. W. B. Saunders Company.
Schafer, _Textbook of Physiology_. The Macmillan Company.
Stiles, _Nutritional Physiology_. W. B. Saunders Company.
Verworn, _General Physiology_. The Macmillan Company.

XIX. FOODS AND DIETARIES

_Problems.--A study of foods to determine:--_
_(a) Their nutritive value._
_(b) The relation of work, environment, age, sex, and
digestibility of foods to diet._
_(c) Their relative cheapness._
_(d) The daily Calorie requirement._
_(e) Food adulteration._
_(f) The relation of alcohol to the human system._

LABORATORY SUGGESTIONS

_Laboratory exercise._--Composition of common foods. The
series of food charts supplied by the United States
Department of Agriculture makes an excellent basis for a
laboratory exercise to determine common foods rich in (_a_)
water, (_b_) starch, (_c_) sugar, (_d_) fats or oils, (_e_)
protein, (_f_) salts, (_g_) refuse.
_Demonstration._--Method of using bomb calorimeter.
_Laboratory and home exercise._--To determine the best
individual balanced dietary (using standard of Atwater,
Chittenden, or Voit) as determined by the use of the
100-Calorie portion.
_Demonstration._--Tests for some common adulterants.
_Demonstration._--Effect of alcohol on protein, _e.g._ white
of egg.
_Demonstration._--Alcohol in some patent medicines.
_Demonstration._--Patent medicines containing acetanilid.
Determination of acetanilid.

Why we Need Food.--A locomotive engine takes coal, water, oxygen, from its environment. A living plant or animal takes organic food, water, and oxygen from its environment. Both the living and nonliving machine do the same thing with this fuel or food. They oxidize it and release the energy in it. But the living organism in addition may use the food to repair parts that have broken down or even build new parts. _Thus food may be defined as something that releases energy or that forms material for the growth or repair of the body of a plant or animal._ The millions of cells of which the body is composed must be given material which will form more living matter or material which can be oxidized to release energy when muscle cells move, or gland cells secrete, or brain cells think.

Nutrients.--Certain nutrient materials form the basis of food of both plants and animals. These have been stated to be _proteins_ (such as lean meat, eggs, the gluten of bread), _carbohydrates_ (starches, sugars, gums, etc.), _fats_ and _oils_ (both animal and vegetable), _mineral matter_ and _water_.

Proteins.--Protein substances contain the element nitrogen. Hence such foods are called nitrogenous foods. Man must form the protoplasm of his body (that is, the muscles, tendons, nervous system, blood corpuscles, the living parts of the bone and the skin, etc.) in part at least from nitrogenous food. Some of this he obtains by eating the flesh of animals, and some he obtains directly from plants (for example, peas and beans). Proteins are the only foods available for tissue building. They may be oxidized to release energy if occasion requires it.

Fats and Oils.--Fats and oils, both animal and vegetable, are the materials from which the body derives part of its energy. The chemical formula of a fat shows that, compared with other food substances, there is very little oxygen present; hence the greater capacity of this substance for uniting with oxygen. The rapid burning of fat compared with the slower combustion of a piece of meat or a piece of bread illustrates this. A pound of butter releases over twice as much energy to the body as does a pound of sugar or a pound of steak. Human fatty tissue is formed in part from fat eaten, but carbohydrate or even protein food may be changed and stored in the body as fat.

Carbohydrates.--We see that the carbohydrates, like the fats, contain carbon, hydrogen, and oxygen. _Carbohydrates are essentially energy-producing foods._ They are, however, of use in building up or repairing tissue. It is certainly true that in both plants and animals such foods pass directly, together with foods containing nitrogen, to repair waste in tissues, thus giving the needed proportion of carbon, oxygen, and hydrogen to unite with the nitrogen in forming the protoplasm of the body.

Inorganic Foods.--Water forms a large part of almost every food substance. It forms about five sixths of a normal daily diet. The human body, by weight, is about two thirds water. About 90 per cent of the blood is water. Water is absolutely essential in passing off waste of the body. When we drink water, we take with it some of the inorganic salts used by the body in the making of bone and in the formation of protoplasm. Sodium chloride (table salt), an important part of the blood, is taken in as a flavoring upon our meats and vegetables. Phosphate of lime and potash are important factors in the formation of bone.

Phosphorus is a necessary substance for the making of living matter, milk, eggs, meat, whole wheat, and dried peas and beans containing small amounts of it. Iron also is an extremely important mineral, for it is used in the building of red blood cells. Meats, eggs, peas and beans, spinach, and prunes, are foods containing some iron.

Some other salts, compounds of calcium, magnesium, potassium, and phosphorus, have been recently found to aid the body in many of its most important functions. The beating of the heart, the contraction of muscles, and the ability of the nerves to do their work appear to be due to the presence of minute quantities of these salts in the body.

Uses of Nutrients.--The following table sums up the uses of nutrients to man:[36]--

Protein Forms tissue \
White of eggs (albumen), (muscles, tendon, }
curd of milk (casein), lean and probably } All serve as
meat, gluten of wheat, etc. fat) } _fuel_ and yield
} _energy_ in form
Fats Form fatty tissue. } of heat and muscular
Fat of meat, butter, olive oil, } strength.
oils of corn and wheat, etc. }
}
Carbohydrates Transformed into }
Sugar, starch, etc. fat. /

Mineral matters (ash) Aid in forming bone,
Phosphates of lime, potash, assist in digestion,
soda, etc. aid in absorption
and in other ways
help the body parts
do their work.
Water used as a vehicle to carry nutrients, and enters into the
composition of living matter.

Footnote 36: Adapted from Atwater, _Principles of Nutrition
and Nutritive Value of Food_, U. S. Department of
Agriculture, 1902.

Common Foods contain the Nutrients.--We have already found in our plant study that various plant foods are rich in different nutrients, carbohydrates forming the chief nutrient in the foods we call cereals, breads, cake, fleshy fruits, sugars, jellies, and the like. Fats and oils are most largely found in nuts and some grains. Animal foods are our chief supply of protein. White of egg and lean meat are almost pure protein and water. Proteins are most abundant, as we should expect, in those plants which are richly supplied with nitrogen; peas and beans, and in grains and nuts. Fats, which are melted into oils at the temperature of the body, are represented by the fat in meats, bacon, pork, lard, butter, and vegetable oils.

Water.--Water is, as we have seen, a valuable part of food. It makes up a very high percentage of fresh fruits and vegetables; it is also present in milk and eggs, less abundant in meats and fish, and is lowest in dried foods and nuts. The amount of water in a given food is often a decided factor in the cost of the given food, as can easily be seen by reference to the chart on page 283.

Refuse.--Some foods bought in the market may contain a certain unusable portion. This we call refuse. Examples of refuse are bones in meat, shells of eggs or of shellfish, the covering of plant cells which form the skins of potatoes or other vegetables. The amount of refuse present also plays an important part in the values of foods for the table. The table[37] on page 276 gives the percentages of organic nutrients, water, and refuse present in some common foods.

Fuel Values of Nutrients.--In experiments performed by Professor Atwater and others, and in the appended tables, the value of food as a source of energy is stated in heat units called _Calories_. _A Calorie is the amount of heat required to raise the temperature of one kilogram of water from zero to one degree Centigrade._ This is about equivalent to raising one pound four degrees Fahrenheit. The fuel value of different foods may be computed in a definite manner. This is done by burning a given portion of a food (say one gram) in the apparatus known as a _calorimeter_. By this means may be determined the number of degrees the temperature of a given amount of water is raised during the process of burning. It has thus been found that a gram of fat will liberate 9.3 Calories of heat, while a gram of starch or sugar only about 4 Calories. The burning value of fat is, therefore, over twice that of carbohydrates. In a similar manner protein has been shown to have about the same fuel value as carbohydrates, _i.e._ 4 Calories to a gram.[38]

Footnote 37 and 38: W. O. Atwater, _Principles of Nutrition
and Nutritive Value of Food_, U. S. Department of
Agriculture, 1902.

The Relation of Work to Diet.--It has been shown experimentally that a man doing hard, muscular work needs more food than a person doing light work. The mere exercise gives the individual a hearty appetite; he eats more and needs more of all kinds of food than a man or boy doing light work. Especially is it true that the person of sedentary habits, who does brain work, should be careful to eat less food and food that will digest easily. His protein food should also be reduced. Rich or hearty foods may be left for the man who is doing hard manual labor out of doors, for any extra work put on the digestive organs takes away just so much from the ability of the brain to do its work.

The Relation of Environment to Diet.--We are all aware of the fact that the body seems to crave more food in winter than in summer. The temperature of the body is maintained at 98.6 deg. in winter as in summer, but much more heat is lost from the body in cold weather. Hence feeding in winter should be for the purpose of maintaining our fuel supply. We need heat-producing food, and we need _more_ food in winter than in summer. We may use carbohydrates for this purpose, as they are economical and digestible. The inhabitants of cold countries get their heat-releasing foods largely from fats. In tropical countries and in hot weather little protein should be eaten and a considerable amount of fresh fruit used.

The Relation of Age to Diet.--As we will see a little later, age is a factor not only in determining the kind but the amount of food to be used. Young children require far less food than do those of older growth or adults. The body constantly increases in weight until young manhood, or womanhood, then its weight remains nearly stationary, varying with health or illness. It is evident that food in adults simply repairs the waste of cells and is used to supply energy. Elderly people need much less protein than do younger persons. But inasmuch as the amount of food to be taken into the body should be in proportion to the body weight, it is also evident that growing children do not, as is popularly supposed, need as much food as grown-ups.

The Relation of Sex to Diet.--As a rule boys need more food than girls, and men than women. This seems to be due to, first, the more active muscular life of the man and, secondly, to the greater amount of fat in the tissues of the woman, making loss of heat less. Larger bodies, because of greater surface, give off more heat than smaller ones. Men are usually larger in bulk than are women,--another reason for more food in their case.

The Relation of Digestibility to Diet.--Animal foods in general may be said to be more completely digested within the body than plant foods. This is largely due to the fact that plant cells have woody walls that the digestive juices cannot act upon. Cereals and legumes are less digestible foods than are dairy products, meat, or fish. This does not mean necessarily that these foods would not agree with you or me but that in general the body would get less nourishment out of the total amount available.

The agreement or disagreement of food with an individual is largely a personal matter. I, for example, cannot eat raw tomatoes without suffering from indigestion, while some one else can digest tomatoes but not strawberries. Each individual should learn early in life the foods that disagree with him personally and leave such foods out of his dietary. For "what is one man's meat may be another man's poison."

The Relation of Cost of Food to Diet.--It is a mistaken notion that the best foods are always the most expensive. A glance at the table (page 283) will show us that both fuel value and tissue-building value is present in some foods from vegetable sources, as well as in those from animal sources, and that the vegetable foods are much cheaper. The American people are far less economical in their purchase of food than most other nations. Nearly one half of the total income of the average workingman is spent on food. Not only does he spend a large amount on food, but he wastes money in purchasing the wrong kinds of food. A comparison of the daily diets of persons in various occupations in this and other countries shows that as a rule we eat more than is necessary to supply the necessary fuel and repair, and that our workingmen eat more than those of other countries. Another waste of money by the American is in the false notion that a large proportion of the daily dietary should be meat. Many people think that the most expensive cuts of meat are the most nutritious. The falsity of this idea may be seen by a careful study of the tables on pages 283 and 286.

The Best Dietary.--Inasmuch as all living substance contains nitrogen, it is evident that protein food must form a part of the dietary; but protein alone is not usable. If more protein is eaten than the body requires, then immediately the liver and kidneys have to work overtime to get rid of the excess of protein which forms a poisonous waste harmful to the body. We must take foods that will give us, as nearly as possible, the proportion of the different chemical elements as they are contained in protoplasm. It has been found, as a result of studies of Atwater and others, that a man who does muscular work requires a little less than one quarter of a pound of protein, the same amount of fat, and about one pound of carbohydrate to provide for the growth, waste, and repair of the body and the energy used up in one day.

The Daily Calorie Requirement.--Put in another way, Atwater's standard for a man at light exercise is food enough to yield 2816 Calories; of these, 410 Calories are from protein, 930 Calories from fat, and 1476 Calories from carbohydrate. That is, for every 100 Calories furnished by the food, 14 are from protein, 32 from fat, and 54 from carbohydrate. In exact numbers, the day's ration as advocated by Atwater would contain about 100 grams or 3.7 ounces protein, 100 grams or 3.7 ounces fat, and 360 grams or 13 ounces carbohydrate. Professor Chittenden of Yale University, another food expert, thinks we need proteins, fats, and carbohydrates in about the proportion of 1 to 3 to 6, thus differing from Atwater in giving less protein in proportion. Chittenden's standard for the same man is food to yield a total of 2360 Calories, of which protein furnishes 236 Calories, fat 708 Calories, and carbohydrates 1416 Calories. For every 100 Calories furnished by the food, 10 are from protein, 30 from fat, 60 from carbohydrate. In actual amount the Chittenden diet would contain 2.16 ounces protein, 2.83 ounces fat, and 13 ounces carbohydrate. A German named Voit gives as ideal 25 Calories from proteins, 20 from fat, and 55 from carbohydrate, out of every 100 Calories; this is nearer our actual daily ration. In addition, an ounce of salt and nearly one hundred ounces of water are used in a day.

A Mixed Diet Best.--Knowing the proportion of the different food substances required by man, it will be an easy matter to determine from the tables and charts shown you the best foods for use in a mixed diet. Meats contain too much nitrogen in proportion to the other substances. In milk, the proportion of proteins, carbohydrates, and fats is nearly right to make protoplasm; a considerable amount of mineral matter being also present. For these reasons, milk is extensively used as a food for children, as it combines food material for the forming of protoplasm with mineral matter for the building of bone. Some vegetables (for example, peas and beans) contain a large amount of nitrogenous material but in a less digestible form than is found in some other foods. Vegetarians, then, are correct in theory when they state that a diet of vegetables may contain everything necessary to sustain life. But a mixed diet containing meat is healthier. A purely vegetable diet contains much waste material, such as the cellulose forming the walls of plant cells, which is indigestible. It has been recently discovered that the outer coats of some grains, as rice, contain certain substances (enzymes) which aid in digestion. In the case of polished rice, when this outer coat is removed the grain has much less food value.

Daily Fuel Needs of the Body.--It has been pointed out that the daily diet should differ widely according to age, occupation, time of year, etc. The following table shows the daily fuel needs for several ages and occupations:--

DAILY CALORIE NEEDS (APPROXIMATELY)

1. For child under 2 years 900 Calories
2. For child from 2-5 years 1200 Calories
3. For child from 6-9 years 1500 Calories
4. For child from 10-12 years 1800 Calories
5. For child from 12-14 (woman, light work, also) 2100 Calories
6. For boy (12-14), girl (15-16), man, sedentary 2400 Calories
7. For boy (15-16) (man, light muscular work) 2700 Calories
8. For man, moderately active muscular work 3000 Calories
9. For farmer (busy season) 3200 to 4000 Calories
10. For ditchers, excavators, etc. 4000 to 5000 Calories
11. For lumbermen, etc. 5000 and more Calories

Normal Heat Output.--The following table gives the result of some experiments made to determine the hourly and daily expenditure of energy of the average normal grown person when asleep and awake, at work or at rest:--

AVERAGE NORMAL OUTPUT OF HEAT FROM THE BODY
==========================================================
| AVERAGE
CONDITIONS OF MUSCULAR ACTIVITY | CALORIES
| PER HOUR
-------------------------------------------+--------------
Man at rest, sleeping | 65 Calories
Man at rest, awake, sitting up | 100 Calories
Man at light muscular exercise | 170 Calories
Man at moderately active muscular exercise | 290 Calories
Man at severe muscular exercise | 450 Calories
Man at very severe muscular exercise | 600 Calories
==========================================================

It is very simple to use such a table in calculating the number of Calories which are spent in twenty-four hours under different bodily conditions. For example, suppose the case of a clerk or school teacher leading a relatively inactive life, who

sleeps for 9 hours x 65 Calories = 585
works at desk 9 hours x 100 Calories = 900
reads, writes, or studies 4 hours x 100 Calories = 400
walks or does light exercise 2 hours x 170 Calories = 340
----
2225

This comes out, as we see, very close to example 6 of the table[39] on page 284.

Footnote 39: The above tables have been taken from the
excellent pamphlet of the Cornell Reading Course, No. 6,
_Human Nutrition_.

How we may Find whether we are Eating a properly Balanced Diet.--We already know approximately our daily Calorie needs and about the proportion of protein, fat, and carbohydrate needed. Dr. Irving Fisher of Yale University has worked out a very easy method of determining whether one is living on a proper diet. He has made up a number of tables, in which he has designated portions of food, each of which furnishes 100 Calories of energy. The tables show the proportion of protein, fat, and carbohydrate in each food, so that it is a simple matter by using such a table to estimate the proportions of the various nutrients in our dietary. We may depend upon taking somewhere near the proper amount of food if we take a diet based upon either Atwater's, Chittenden's, or Voit's standard. One of the most interesting and useful pieces of home work that you can do is to estimate your own personal dietary, using the tables giving the 100-Calorie portion to see if you have a properly balanced diet. From the table on page 286 make out a simple dietary for yourself for one day, estimating your own needs in Calories and then picking out 100-Calorie portions of food which will give you the proper proportions of protein, fat, and carbohydrate.

TABLE OF 100 CALORIE PORTIONS--MODIFIED FROM FISHER

============================================================================
| |WT. IN| CAL. FURNISHED| PRICE
| | OZ. |----+----+-----+--------+------
|PORT. CONTAINING | 100 | | |CAR- | | 100
FOOD | 100 CALORIES | CAL.|PRO-| FAT|BOHY-| 1 LB. | CAL.
| | PORT.|TEIN| |DRATE| | POR.
------------------+------------------+------+----+----+-----+--------+------
Oysters |1 doz. | 6.8 | 49 |22 | 29 | .175 | .07
Bean soup |1/2 small serving | 2.6 | 24 |12 | 64 | | .007
Cream of corn |2/3 ordin. serv. | 3.1 | 11 |58 | 31 | | .02
Vegetable soup |1/2 ordin. serv. | 2.4 | 8 |89 | 3 | | .01
Cod fish (fresh) |ordin. serv. | 5 | 95 | 5 | 0 | .12 | .04
Salmon (canned) |small serv. | 1.75 | 45 |55 | 0 | .22 | .03
Chicken |1/2 large serv. | 1.75 | 39 |56 | 5 | .22 | .05
Veal cutlet |2/3 large serv. | 2.4 | 54 |46 | 0 | .28 | .045
Beef, corned |1/2 large serv. | 1.0 | 15 |85 | 0 | .16 | .01
Beef, sirloin | small serv. | 1.6 | 33 |67 | 0 | .34 | .04
Beef, round | small serv. | 1.8 | 39 |61 | 0 | .24 | .025
Ham, lean | ordin. serv. | 1.1 | 28 |72 | 0 | .22 | .015
Lamb chops |1/2 ordin. serv. | 1.0 | 24 |76 | 0 | .20 | .013
Mutton, leg | ordin. serv. | 1.2 | 35 |65 | 0 | .20 | .015
Eggs, boiled |1 large egg | 2.1 | 32 |68 | 0 |.30 doz.| .025
Eggs, scrambled |1-1/3 ordin. serv.| 2.5 | 37 |58 | 5 |.30 doz.| .03
Beans, baked | side dish | 2.66 | 21 |18 | 61 | .08 | .013
Potatoes, mashed | ordin. serv. | 3.2 | 10 |25 | 65 | .02 | .005
Macaroni |1/3 large serv. | .95 | 15 | 3 | 82 | .10 | .01
Potato salad | ordin. serv. | 2.25 | 10 |57 | 33 | .20 | .025
Tomatoes, sliced |4 large serv. |15. | 15 |16 | 69 | .10 | .10
Rolls, plain |1 large roll | 1.2 | 12 | 7 | 81 |.10 doz.| .01
Butter | ordin. pat | .44 | 5 |99.5| | .35 | .01
Wheat bread |1 small slice | .96 | 15 | 5 | 80 | .07 | .005
Chocolate cake |1/2 ord. sq. piece| .98 | 7 |22 | 71 | .32 | .02
Gingerbread |1/2 ord. sq. piece| .96 | 6 |23 | 71 | .16 | .01
Custard pudding | ordin. serv. | 3.25 | 18 |42 | 40 | .15 | .03
Rice pudding | very small serv.| 2.65 | 8 |13 | 79 | .13 | .02
Apple pie |1/3 piece | 1.3 | 5 |32 | 63 | | .013
Cheese, American |1-1/2 cu. in. | .77 | 25 |73 | 2 | .19 | .01
Crackers (soda) |2 crackers | .9 | 10 |20 | 70 | .10 | .007
Currant jelly |2 heap. spoons | 1.1 | 2 | 0 | 98 | .40 | .025
Sugar |3 teaspoons | .86 | 0 | 0 | 100 | .06 | .003
Milk as bought | small glass | 4.9 | 19 |52 | 29 | .05 | .015
Milk, cond., sweet|4 teaspoons | 1.06 | 10 |23 | 67 | | .01
Oranges |1 large one | 9.4 | 6 | 3 | 91 | | .025
Peanuts |13 double ones | .62 | 20 |63 | 17 | | .004
Almonds, shelled |8-15 | .53 | 13 |77 | 10 | | .025
============================================================================

From the preceding table plan a well-balanced and cheap dietary for one day for a family of five, two adults and three children. Make a second dietary for the same time and same number of people which shall give approximately the same amount of tissue and energy producing food from more expensive materials.

Food Waste in the Kitchen.--Much loss occurs in the improper cooking of foods. Meats especially, when overdone, lose much of their flavor and are far less easily digested than when they are cooked rare. The chief reasons for cooking meats are that the muscle fibers may be loosened and softened, and that the bacteria or other parasites in the meat may be killed by the heat. The common method of frying makes foods less digestible. Stewing is an economical as well as healthful method. A good way to prepare meat, either for stew or soup, is to place the meat, cut in small pieces, in cold water, and allow it to simmer for several hours. Rapid boiling toughens the muscle fibers by the too rapid coagulation of the albuminous matter in them, just as the white of egg becomes tough when boiled too long. Boiling and roasting are excellent methods of cooking meat. In order to prevent the loss of the nutrients in roasting, it is well to baste the meat frequently; thus a crust is formed on the outer surface of the meat, which prevents the escape of the juices from the inside.

Vegetables are cooked in order that the cells containing starch grains may be burst open, thus allowing the starch to be more easily attacked by the digestive fluids. Inasmuch as water may dissolve out nutrients from vegetable tissues, it is best to boil them rapidly in a small amount of water. This gives less time for the solvent action to take place. Vegetables should be cooked with the outer skin left on when it is possible.

Adulterations in Foods.--The addition of some cheaper substance to a food, or the subtraction of some valuable substance from a food, with the view to cheating the purchaser, is known as _adulteration_. Many foods which are artificially manufactured have been adulterated to such an extent as to be almost unfit for food, or even harmful. One of the commonest adulterations is the substitution of grape sugar (glucose) for cane sugar. Glucose, however, is not a harmful adulterant. It is used largely in candy making. Flour and other cereal foods are sometimes adulterated with some cheap substitutes, as bran or sawdust. Alum is sometimes added to make flour whiter. Probably the food which suffers most from adulteration is milk, as water can be added without the average person being the wiser. By means of an inexpensive instrument known as a _lactometer_, this cheat may easily be detected. In most cities, the milk supply is carefully safeguarded, because of the danger of spreading typhoid fever from impure milk (see Chapter XX). Before the pure food law was passed in 1906, milk was frequently adulterated with substances like formalin to make it keep sweet longer. Such preservatives are harmful, and it is now against the law to add anything whatever to milk.

Coffee, cocoa, and spices are subject to great adulteration; cottonseed oil is often substituted for olive oil; butter is too frequently artificial; while honey, sirups of various kinds, cider and vinegar, have all been found to be either artificially made from cheaper substitutes or to contain such substitutes.

Pure Food Laws.--Thanks to the National Pure Food and Drug Law passed by Congress in 1906, and to the activity of various city and state boards of health, the opportunity to pass adulterated foods on the public is greatly lessened. This law compels manufacturers of foods or medicines to state the composition of their products on the labels placed on the jars or bottles. So if a person reads the label he can determine exactly what he is getting for his money.

Impure Water.--Great danger comes from drinking impure water. This subject has already been discussed under Bacteria, where it was seen that the spread of typhoid fever in particular is due to a contaminated water supply. As citizens, we must aid all legislation that will safeguard the water used by our towns and cities. Boiling water for ten minutes or longer will render it safe from all organic impurities.

Stimulants.--We have learned that food is anything that supplies building material or releases energy in the body; but some materials used by man, presumably as food, do not come under this head. Such are tea and coffee. When taken in moderate quantities, _they produce a temporary increase in the vital activities_ of the person taking them. This is said to be a stimulation; and material taken into the digestive tract, producing this, is called a _stimulant_. In moderation, tea and coffee appear to be harmless. Some people, however, cannot use either without ill effects, even in small quantity. It is the _habit_ formed of relying upon the stimulus given by tea or coffee that makes them a danger to man. Cocoa and chocolate, although both contain a stimulant, are in addition good foods, having from 12 per cent to 21 per cent of protein, from 29 per cent to 48 per cent fat, and over 30 per cent carbohydrate in their composition.

Is Alcohol a Food?--The question of the use of alcohol has been of late years a matter of absorbing interest and importance among physiologists. A few years ago Dr. Atwater performed a series of very careful experiments by means of the respiration calorimeter, to ascertain whether alcohol is of use to the body as food.[40] In these experiments the subjects were given, instead of their daily allotment of carbohydrates and fats, enough alcohol to supply the same amount of energy that these foods would have given. The amount was calculated to be about two and one half ounces per day, about as much as would be contained in a bottle of light wine.[41] This alcohol was administered in small doses six times during the day. Professor Atwater's results may be summed up briefly as follows:--

1. The alcohol administered was almost all oxidized in the body.

2. The potential energy in the alcohol was transformed into heat or muscular work.

3. The body did about as well with the rations including alcohol as it did without it.

Footnote 40: Alcohol is made up of carbon, oxygen, and
hydrogen. It is very easily oxidized, but it cannot, as is
shown by the chemical formula, be of use to the body in
tissue building, because of its lack of nitrogen.

Footnote 41: Alcoholic beverages contain the following
proportions of alcohol: beer, from 2 to 5 per cent; wine,
from 10 to 20 per cent; liquors, from 30 to 70 per cent.
Patent medicines frequently contain as high as 60 per cent
alcohol. (See page 294.)

The committee of fifty eminent men appointed to report on the physiological aspects of the drink problem reported that a large number of scientific men state that they are in the habit of taking alcoholic liquor in small quantities, and many report that they do not _feel_ harm thereby. A number of scientists seem to agree that within limits alcohol may be a kind of food, although a very _poor_ food.

On the other hand, we know that although alcohol may technically be considered as a food, it is a very unsatisfactory food and, as the following statements show, it has an effect on the body tissues which foods do not have.

Professor Chittenden of Yale College, in discussing the food problem of alcohol, writes as follows:

"It is true that alcohol in moderate quantities may serve as a food,
_i.e._ it can be oxidized with the liberation of heat. It may to some
extent take the place of fat and carbohydrates, but it is not a
perfect substitute for them, and for this reason alcohol has an action
that cannot be ignored. It reduces liver oxidation. It therefore
presents a dangerous side wholly wanting in carbohydrates and fat. The
latter are simply burned up to carbonic acid and water or are
transformed to glycogen and fat, but alcohol, although more easily
oxidized, is at all times liable to obstruct, in a measure at least,
the oxidative processes of the liver and probably of other tissues
also, thereby throwing into the circulation bodies, such as uric acid,
which are harmful to health, a fact which at once tends to draw a
distinct line of demarcation between alcohol and the two
non-nitrogenous foods, fat and carbohydrates. Another matter must be
emphasized, and it is that the form in which alcohol is taken is of
importance. Port wine, for instance, has more influence on the amount
of uric acid secreted than an equivalent amount of alcohol has in some
other form. To conclude: as an adjunct to the ordinary daily diet of
the healthy man alcohol cannot be considered as playing the part of a
true non-nitrogenous food."--Quoted in _American Journal of
Inebriety_, Winter, 1906.

Effect of Alcohol on Living Matter.--If we examine raw white of egg, we find a protein which closely resembles protoplasm in its chemical composition; it is called albumen. Add to a little albumen in a test tube some 95 per cent alcohol and notice what happens. As soon as the alcohol touches the albumen the latter coagulates and becomes hard like boiled white of egg. Shake the alcohol with the albumen and the entire mass soon becomes a solid. This is because the alcohol draws the water out of the albumen. It has been shown that albumen is somewhat like protoplasm in structure and chemical composition. Strong alcohol acts in a similar manner on living matter when it is absorbed by the living body cells. It draws water from them and hardens them. It has a chemical and physical action upon living matter.

Alcohol a Poison.--But alcohol is also in certain quantities a poison. _A commonly accepted definition of a poison is that it is any substance which, when taken into the body, tends to cause serious detriment to health, or the death of the organism._ That alcohol may do this is well known by scientists.

It is a matter of common knowledge that alcohol taken in small quantities does not do any _apparent_ harm. But if we examine the vital records of life insurance companies, we find a large number of deaths directly due to alcohol and a still greater number due in part to its use. In the United States every year there are a third more deaths from alcoholism and cirrhosis of the liver (a disease _directly_ caused by alcohol) than there are from typhoid fever. The poisonous effect is not found in small doses, but it ultimately shows its harmful effect. Hardening of the arteries, an old-age disease, is rapidly becoming in this country a disease of the middle aged. From it there is no escape. It is chiefly caused by the cumulative effect of alcohol. The diagram following, compiled by two English life insurance companies that insure moderate drinkers and abstainers, shows the death rate to be considerably higher among those who use alcohol.

Dr. Kellogg, the founder of the famous Battle Creek Sanitarium, points out that strychnine, quinine, and many other drugs are oxidized in the body but surely cannot be called foods. The following reasons for not considering alcohol a food are taken from his writings:--

"1. A habitual user of alcohol has an intense craving for
his accustomed dram. Without it he is entirely unfitted for
business. One never experiences such an insane craving for
bread, potatoes, or any other particular article of food.

"2. By continuous use the body acquires a tolerance for
alcohol. That is, the amount which may be imbibed and the
amount required to produce the characteristic effects first
experienced gradually increase until very great quantities
are sometimes required to satisfy the craving which its
habitual use often produces. This is never the case with
true foods.... Alcohol behaves in this regard just as does
opium or any other drug. It has no resemblance to a food.

"3. When alcohol is withdrawn from a person who has been
accustomed to its daily use, most distressing effects are
experienced.... Who ever saw a man's hand trembling or his
nervous system unstrung because he could not get a potato or
a piece of cornbread for breakfast? In this respect, also,
alcohol behaves like opium, cocaine, or any other enslaving
drug.

"4. Alcohol lessens the appreciation and the value of brain
and nerve activity, while food reenforces nervous and mental
energy.

"5. Alcohol as a protoplasmic poison lessens muscular power,
whereas food increases energy and endurance.

"6. Alcohol lessens the power to endure cold. This is true
to such a marked degree that its use by persons accompanying
Arctic expeditions is absolutely prohibited. Food, on the
other hand, increases ability to endure cold. The
temperature after taking food is raised. After taking
alcohol, the temperature, as shown by the thermometer, is
lowered.

"7. Alcohol cannot be stored in the body for future use,
whereas all food substances can be so stored.

"8. Food burns slowly in the body, as it is required to
satisfy the body's needs. Alcohol is readily oxidized and
eliminated, the same as any other oxidizable drug."

The Use of Tobacco.--A well-known authority defines a narcotic as a substance "_which directly induces sleep, blunts the senses, and, in large amounts, produces complete insensibility_." Tobacco, opium, chloral, and cocaine are examples of narcotics. Tobacco owes its narcotic influence to a strong poison known as nicotine. Its use in killing insect parasites on plants is well known. In experiments with jellyfish and other lowly organized animals, the author has found as small a per cent as one part of nicotine to one hundred thousand parts of sea water to be sufficient to profoundly affect an animal placed within it. The illustration here given shows the effect of nicotine upon a fish, one of the vertebrate animals. Nicotine in a pure form is so powerful a poison that two or three drops would be sufficient to cause the death of a man by its action upon the nervous system, especially the nerves controlling the beating of the heart. This action is well known among boys training for athletic contests. The heart is affected; boys become "short-winded" as a result of the action on the heart. It has been demonstrated that tobacco has, too, an important effect on muscular development. The stunted appearance of the young smoker is well known.

Use and Abuse of Drugs.--The American people are addicted to the use of drugs, and especially patent medicines. A glance at the street-car advertisements shows this. Most of the medicines advertised contain alcohol in greater quantity than beer or wine, and many of them have opium, morphine, or cocaine in their composition. Paregoric and laudanum, medicines sometimes given to young children, are examples of dangerous drugs that contain opium. Dr. George D. Haggard of Minneapolis has shown by many analyses that a large number of the so-called "malts," "malt extracts," and "tonics," including several of the best known and most advertised on the market, are simply disguised beers and, frequently, very poor beers at that. These drugs, in addition to being harmful, affect the person using them in such a manner that he soon feels the need for the drug. Thus the drug habit is formed,--a condition which has wrecked thousands of lives. A number of articles on patent medicines recently appeared in a leading magazine and have been collected and published under the title of _The Great American Fraud_. In this booklet the author points out a number of different kinds of "cures" and patent medicines. The most dangerous are those headache or neuralgia cures containing _acetanilid_. This drug is a heart depresser and should not be used without medical advice. Another drug which is responsible for habit formation is _cocaine_. This is often found in catarrh or other cures. Alcohol is the basis of all tonics or "bracers." Every boy and girl should read this booklet so as to be forearmed against evils of the sort just described.

REFERENCE READING ON FOODS

Hunter, _Laboratory Problems in Civic Biology._ American Book
Company.
Allen, _Civics and Health._ Ginn and Company.
Bulletin 13, American School of Home Economics, Chicago.
Cornell University Reading Course, Buls. 6 and 7, _Human
Nutrition._
Davison, _The Human Body and Health._ American Book Company.
Jordan, _The Principles of Human Nutrition._ The Macmillan
Company.
Kehler, L. F., _Habit-forming Agents._ Farmers' Bulletin 393,
U. S. Dept. of Agri.
Lusk, _Science and Nutrition._ W. B. Saunders Company.
Norton, _Foods and Dietetics._ American School of Home Economics.
Olsen, _Pure Foods._ Ginn and Company.
Sharpe, _A Laboratory Manual for the Solution of Problems in
Biology,_ pp. 226-240. American Book Company.
Stiles, _Nutritional Physiology._ W. B. Saunders Company.
_The Great American Fraud._ American Medical Association, Chicago.
_The Propaganda for Reform in Proprietary Medicines._ Am.
Medical Association.
Farmers' Bulletin: numbers 23, 34, 42, 85, 93, 121, 128, 132,
142, 182, 249, 295, 298.
Reprint from Yearbook, 1901, Atwater, _Dietaries in Public
Institutions._
Reprint from Yearbook, 1902, Milner, _Cost of Food related to
its Nutritive Value._
Experiment Station, Circular 46, Langworthy, _Functions and
Uses of Food._

XX. DIGESTION AND ABSORPTION

_Problems.--To determine where digestion takes place by examining_:--
_(a) The functions of glands._
-(b) The work done in the mouth._
-(c) The work done in the stomach._
-(d) The work done in the small intestine._
-(e) The function of the liver._
_To discover the absorbing apparatus and how it is used._

LABORATORY SUGGESTIONS

_Demonstration of food tube of man_ (manikin).--Comparison
with food tube of frog. Drawing (comparative) of food tube
and digestive glands of frog and man.
_Demonstration of simple gland._--(Microscopic preparation.)
_Home experiment and laboratory demonstration._--The
digestion of starch by saliva. Conditions favorable and
unfavorable.
_Demonstration experiment._--The digestion of proteins with
artificial gastric juice. Conditions favorable and
unfavorable.
_Demonstration._--An emulsion as seen under the compound
microscope.
_Demonstration._--Emulsification of fats with artificial
pancreatic fluid. Digestion of starch and protein with
artificial pancreatic fluid.
_Demonstration_ of "tripe" to show increase of surface of
digestive tube.
_Laboratory or home exercise._--Make a table showing the
changes produced upon food substances by each digestive
fluid, the reaction (acid or alkaline) of the fluid, when
the fluid acts, and what results from its action.

Purpose of Digestion.--We have learned that starch and protein food of plants are formed in the leaves. A plant, however, is unable to make use of the food in this condition. Before it can be transported from one part of the plant body to another, it is changed into a soluble form. In this state it can be passed from cell to cell by the process of osmosis. Much the same condition exists in animals. In order that food may be of use to man, it must be changed into a state that will allow of its passage in a soluble form through the walls of the alimentary canal, or food tube. This is done by the enzymes which cause digestion. It will be the purpose of this chapter to discover where and how digestion takes place in our own body.

Alimentary Canal.--In all vertebrate animals, including man, food is taken in the mouth and passed through a _food tube_ in which it is digested. This tube is composed of different portions, named, respectively, as we pass from the _mouth_ downward, the _gullet_, _stomach_, _small_ and _large intestine_, and _rectum_.

Comparison of Food Tube of a Frog and Man.--If we compare the food tube of a dissected frog with the food tube of man (as shown by a manikin or chart), we find part for part they are much the same. But we notice that the intestines of man, both small and large, are relatively longer than in the frog. We also notice in man the body cavity or space in which the internal organs rest is divided in two parts by a wall of muscle, the _diaphragm_, which separates the heart and lungs from the other internal organs. In the frog no muscular diaphragm exists. In the frog we can see plainly the silvery transparent _mesentery_ or double fold of the lining of the body cavity in which the organs of digestion are suspended. Numerous blood vessels can be found especially in the walls of the food tube.

Glands.--In addition to the alimentary canal proper, we find a number of _digestive glands_, varying in size and position, connected with the canal.

What a Gland Does. Enzymes.--In man there are the saliva gland of the mouth, the gastric glands of the stomach, the pancreas and liver, the two latter connected with the small intestine, and the intestinal glands in the walls of the intestine. Besides glands which aid in digestion there are several others of which we will speak later. As we have already learned, a gland is a collection of cells which takes up material from within the body and manufactures from it something which is later poured out as a secretion. An example of a gland in plants is found in the nectar-secreting cells of a flower.

Certain substances, called _enzymes_, formed by glands cause the digestion of food. The enzymes secreted by the cells of the glands and poured out into the food tube act upon insoluble foods so as to change them to a soluble form. They are the product of the activity of the cell, although they are not themselves alive. We do not know much about enzymes themselves, but we can observe what they do. Some enzymes render soluble different foods, others work in the blood, still others probably act within any cell of the body as an aid to oxidation, when work is done. Enzymes are very sensitive to changes in temperature and to the degree of _acidity_ or _alkalinity_[42] of the material in which they act. We will find that the enzymes found in glands in the mouth will not act long in the stomach because of the change from an alkaline surrounding in the mouth to that of an acid in the stomach. Enzymes seem to be able to work indefinitely, providing the surroundings are favorable. A small amount of digestive fluid, if it had long enough to work, could therefore digest an indefinite amount of food.

Footnote 42: The teacher should explain the meaning of these
terms.

Gland Structure.--The entire inner surface of the food tube is covered with a soft lining of _mucous membrane_. This is always moist because certain cells, called _mucus cells_, empty out their contents into the food tube, thus lubricating its inner surface. When a large number of cells which have the power to secrete fluids are collected together, the surface of the food tube may become indented at this point to form a pitlike _gland_. Often such depressions are branched, thus giving a greater secreting surface, as is seen in the figure on page 298. The cells of the gland are always supplied with blood vessels and nerves, for the secretions of the glands are under the control of the nervous system.

How a Gland Secretes.--We must therefore imagine that as the blood goes to the cells of a gland it there loses some substances which the gland cells take out and make over into the particular enzyme that they are called upon to manufacture. Under certain conditions, such as the sight or smell of food, or even the desire for it, the activity of the gland is stimulated. It then pours out its secretion containing the digestive enzyme. Thus a gland does its work.

Salivary Glands.--We are all familiar with the substance called _saliva_ which acts as a lubricant in the mouth. Saliva is manufactured in the cells of three pairs of glands which empty into the mouth, and which are called, according to their position, the _parotid_ (beside the ear), the _submaxillary_ (under the jawbone), and the _sublingual_ (under the tongue).