Lesson CLXXXVII

Bacteria

Leading thought—Bacteria are such small plants that we cannot see them without the aid of a microscope, but they can be planted and will grow. The object of this lesson is to enforce cleanliness.

Method—Experiment A—The bread used for the mold experiment is likely to develop spots of yellow, red or purple upon it, and cultures from these spots may be used in this lesson as follows: Take some vials, boil them and their corks, and nearly fill them with milk that has been boiled. Take the head of a pin or hairpin, sterilize the point by holding in a flame, let it cool, touch one of the yellow spots on the bread with the point, being careful to touch nothing else, and thrust the point with the bacteria on it into the milk; then cork the vials.

Experiment B—Prepare gelatin as for the table but do not sweeten. Pour some of this gelatin on clean plates or saucers. After it has cooled let one of the children touch lightly the gelatin in one saucer for a few seconds with his soiled finger. Note the place. Ask him to wash his hands thoroughly with soap and then apply a finger to the surface of the gelatin in the other plate. Cover both plates to keep out the dust and leave them for two or three days in a dark place. The plates touched by the soiled finger will show a clouded growth in the gelatin; the other plate will show a few irregular, scattered growths or none.

Experiment C—Take a slice of boiled potato, place in a saucer, leave it uncovered for a time or blow dust upon it, label with date, then cover with a tumbler to keep from drying and place in a cool, somewhat dark place.

The pupils should examine all these cultures every day and make the following notes:

Experiment A—How soon did you observe a change in the color of the milk? How can you tell when the milk is full of the bacteria? How do you know that the bacteria in the milk was transplanted by the pin?

Experiment B—Can you see that the gelatin is becoming clouded where the soiled finger touched it? This is a growth of the bacteria which were on the soiled finger.

Experiment C—What change has taken place in the appearance of the slice of potato? Are there any spots growing upon it? What is the odor? What makes the spots? Describe the shape of the spots. The color. Are any of them pimple-shaped? Make a drawing of the slice of potato showing the bacteria spots. What are the bacteria doing to the potato? Take a part of the slice of potato with the bacteria spots upon it, and put it in the sunshine. What happens? Compare this with the part kept in the dark.

After this lesson the children should be asked the following questions.

1. Why should the hands always be washed before eating?

2. Why should the finger nails be kept clean?

3. Why should we never bite the finger nails nor put the fingers in the mouth?

4. Why should we never put coins in the mouth?

5. Why should wounds be carefully cleansed and dressed at once?

6. Why should clothing, furniture and the house be kept free from dust?

7. Why should sweeping be done as far as possible without raising dust?

8. Why are hardwood floors more healthful than carpets?

9. Why is a damp cloth better than a feather duster for removing dust?

10. Why should the prohibition against spitting in public places be strictly enforced?

11. Why should the dishes, clothes and other articles used by sick persons be kept distinctly separate from those used by well members of the family?

12. Why should food not be exposed for sale on the street?

13. Why, during an epidemic, should water be boiled before drinking?

“This habit of looking first at what we call the beauty of objects is closely associated with the old conceit that everything is made to please man: man is only demanding his own. It is true that everything is man’s because he may use it or enjoy it, but not because it was designed and ‘made’ for ‘him’ in the beginning. This notion that all things were made for man’s special pleasure is colossal self-assurance. It has none of the humility of the psalmist, who exclaimed, ‘What is man, that thou art mindful of him?’”

“‘What were these things made for, then?’ asked my friend. Just for themselves! Each thing lives for itself and its kind, and to live is worth the effort of living for man or bug. But there are more homely reasons for believing that things were not made for man alone. There was logic in the farmer’s retort to the good man who told him that roses were made to make man happy. ‘No, they wa’n’t’, said the farmer, ‘or they wouldn’t a had prickers.’ A teacher asked me what snakes are ‘good for.’ Of course there is but one answer: they are good to be snakes.” —“The Nature Study Idea”, L. H. Bailey.