It is difficult to find a spot on the earth’s surface where bacteria do not abound. They are most abundant in the air of crowded cities, but also are found in the air of mid-ocean. The air of high mountain tops is comparatively free from bacteria as also the air of the Arctic regions. Even the sea water near the poles contains few microbes. Bacteria grow with great rapidity in the warm moist climate of the tropics, but fortunately their development in hot countries is greatly hindered by the disinfecting effects of the actinic rays of the tropical sun.
Bacteria of the Skin
Bacteria which are capable of infecting the body cells and causing suppuration are constantly found upon the skin in countless numbers. These round streptococci infest especially the oil glands of the skin and the hair follicles. The so-called “skin worms” or comedones consist chiefly of colonies of bacteria.
The Intestinal Flora
The plants which grow in a locality are known as its flora. Bacteriologists have applied the same term to the various species of low vegetable forms known as bacteria that grow in the alimentary canal.
The flora of every locality may be divided into two classes, one useful, the other useless or pernicious.
The group of useful plants comprises food plants, flowers, trees and other plants that may be in some way utilized. The second class is made up of weeds, poisonous or useless plants.
A similar classification may be made of the intestinal flora. Certain species are useful and native to the alimentary tract, the acid formers. These render useful service to the body by pre-venting the growth of the harmful bacteria.
Another class, sometimes known as “wild” bacteria, or “meat bacilli,” give rise to various harmful effects through poisons that they pro-duce and in other ways.
The entire alimentary tract harbors multitudes of bacteria. The saliva swarms with bacteria which are ready to develop enormously if favor-able conditions are supplied, and may attack the teeth and the gums, as seen in dental decay and pyorrhea. So long as the blood is maintained in a state of high resistance the saliva protects the mouth and the teeth by inhibiting or hindering the growth of bacteria; but when the blood becomes deteriorated, the saliva loses its protective power, the mouth germs become more numerous and more virulent, the tongue becomes coated and the breath foul, and the teeth become coated with a viscid mucus and finally show evidence of decay. Roger and others have isolated many different species of bacteria from the saliva.
The cavities of the nose and throat likewise harbor many species of bacterianot only the common pus-forming microbes, streptococci and staphylococci, but the dangerous micro-organisms of pneumonia, diphtheria, and meningitis.
Many of the species of bacteria found in the mouth are also found in the stomach. Fortunately the stomach is protected by the gastric juice, which is a powerful disinfectant so long as it contains the normal amount of hydrochloric acid. The normal stomach always contains enough gastric acid to protect it. The diseased stomach, however, often lacks this important means of defense.
When this is the case, the bacteria of the mouth easily pass through the stomach and establish themselves in the intestine, where they find conditions more favorable for their growth and development, especially in the colon.
Roger enumerates one hundred and sixty different species of microbes that infest the alimentary canal, more than one-third being known to produce poisons. The largest number of these various species are found in the colon, where conditions for the growth of bacteria of the worst kind are most favorable. Here the unusable residues of the food, together with mucus, bile, and other body wastes, furnish just the material best suited to encourage the growth of putrefactive and other disease-producing bacteria.
The presence of these dangerous enemies of life and health is made obvious by the highly offensive and often loathsome character of the stools or bowel discharges. Putrid, rancid, ammoniacal, nauseating odors always indicate putrefaction, and from the intensity of the foul odors may be judged the intensity of the putrefactive process.