The New Student's Reference Work/Bacteria

Bacte′ria, an immense group of extremely small plants which have attracted great attention on account of their relation to man and his interests. They are the smallest known of living organisms, whose adult bodies are sometimes barely visible under the highest powers of the microscope. They multiply by division with wonderful rapidity, and occur in the air, in the water, in the soil, in the bodies of plants and animals. Some of them are harmless, some are useful, and some are exceedingly dangerous. They are the agents of the processes known as fermentation and decay, inducing fruit juices, milk, etc. to sour, and also pus to form in connection with wounds and decay. What is called antiseptic surgery is the use of various means to exclude bacteria and so prevent inflammation and decay. As producers of disease, bacteria are known by various names, such as bacilli, microbes, germs, etc. They are the causes of contagious diseases, such as pear-blight and melon-wilt among plants, and such human diseases as tuberculosis, cholera, diphtheria, typhoid fever, etc. From the fact that bacteria are mostly ciliated and have powers of locomotion, they are associated in the popular mind with animals.