" Good Germs "

A half century of living under the tutelage of Pasteur and his successors has taught us that most disease is caused by " deadly " bacteria* and has inspired a healthy fear of the teeming microbe world. It may come as a surprise to many to find that the "pathogenic" (disease-producing) germs are relatively few in number, and their influence is far outweighed by the " good germs," whose action is not only beneficent but even essential to the maintenance of the human species. Dr. Arthur I. Kendall, professor of bacteriology, Dean of Northwestern University Medical School, and author of Bacteriology--General, Pathological, Intestinal, tells the story in simple readable language in his latest book written for his daughter, Alice, to supplement her high school science course.

The best work the bacteria do is the demolition of organic compounds (human and animal waste, dead bodies and plants) into simpler nitrates and carbonates -- forms which plants can utilize again. Without the participation of microbes in this cycle, life upon this planet would inevitably cease. Without them, civilized communities would long ago have been overwhelmed in their own waste products. Spread upon the surface of the earth, these become harmless through microbic activity. These upper layers of the soil are the ancestral home of the bacteria, where they are concentrated most thickly. Germs which break down organic matter in the soil are frequently attached to the roots of legumes (beans, peas, clover), and act as " nitrogen-fixers" for the vegetable kingdom.

Some exciting statistics of Dean Kendall's: Many microbes reproduce (by fission) in 15 minutes. If this rate were kept up for 96 generations (24 hours), the descendants of one parent cell would number more than 78 octillions. (There are only 31 trillion seconds in a million years!) These unthinkable populations are held in check, however, by competition, lack of food, poisons, etc. At a moderate estimate, 30 trillions of bacteria are excreted from one human body each day. Yet these 30 trillions weigh, on the average, only two ounces. The biggest known microbe is the bacillus buetschlii (found in the cockroach), which may be 50 microns (one 500th of an inch) in length and about one-tenth as wide. Among the smallest is the bacillus influenzae (0.8x0.3 microns), although the filterable viruses are believed to consist of ultramicroscopic organisms very much smaller. The most active bacteria move about .0012 of an inch a second. In proportion to size, this would mean a speed of more than a mile a minute for a man.

Other important constructive activities of bacteria:

1) Their chemical use to identify and standardize carbohydrates, particularly sugars (the favorite food of bacteria).

2) Purification of sewage through layers of bacteria (called Schmutzdecke) at the top of sand filters. This method, while important in small communities and in the early stages of sewage sanitation (about 1870-1910), becomes too costly in large cities because of the land space required.

3) Purification of drinking water by similar methods (now largely replaced by chlorination--the addition of one part of chlorine gas to a million parts of water).

4) " Retting " of flax, i.e.. removing the stalks of the plant from the long linen fibers by immersion in bacterial streams.

5) Tanning of leather, by the fermentation of hemlock bark.

6) Production of artificial rubber by fermentation from starch (intermediate stages: butyl alcohol and " isoprene ").

7) Manufacturing of vinegar by action of acetic acid bacteria (obtained from "mother of vinegar") on alcohol and the oxygen of the air.

8) Souring or curdling of milk for preservation in warm climates (by lactic acid bacteria).

9) Protection of nursing children against intestinal diseases by luxuriant growth of lactic-acid bacteria in the alimentary canal. Cow's milk is less favorable to this growth than mother's milk.

10) Use of lactic acid cultures as " starters" in churning butter, in the manufacture of sauerkraut, and in preparing ensilage on farms.

* Bacteria (singular, "bacterium) is the correct scientific name for all microscopic unicellular organisms of the vegetable kingdom, except the yeasts, molds, etc. Germs and microbes are popular names for the same thing. The corresponding animal organisms are called protozoa. The distinction is rather arbitrary. Bacteria are divided into three groups, the cocci (spherical or berry-shaped), the bacilli (elongated or rod-shaped), the spirilla (twisted or spiral-shaped). The bacilli are by far the most numerous.

/-CIVILIZATION AND THE MICROBE--Arthur I. Kendall -- Houghton, Mifflin $2.50).