Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] 170 BOTANY alcohol in cider, and by a chemical process change the alcohol to vinegar. Others, called the lactic acid bacteria, bring about the souring of milk by acting on the sugar found in the milk. Thus they aid in butter and cheese making. Others give the flavor to cheese or butter. Some are of great economic importance, as we have already seen, in their relation to the roots of some plants, where they fix nitrogen in such a for
Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] 170 BOTANY alcohol in cider, and by a chemical process change the alcohol to vinegar. Others, called the lactic acid bacteria, bring about the souring of milk by acting on the sugar found in the milk. Thus they aid in butter and cheese making. Others give the flavor to cheese or butter. Some are of great economic importance, as we have already seen, in their relation to the roots of some plants, where they fix nitrogen in such a form that it can be used by the plants as food. Bacteria seem to prefer to feed upon sub- stances that contain nitrogen, this element being necessary to Microscopic appearance of ordinary milk showing fat globules and bacteria. The cluster of bacteria on left side are lactioracid-forming germs. (H. L. Russell, Wis. Bui. No. 62.) form protoplasm. They are found in great numbers upon all nitrogenous foods, as milk, meats, fish, etc. Feeding upon such substances, they decompose them and cause decay to take place. Typhoid. — Such bacteria as are parasitic in the human body may cause disease. Sometimes the harm is done by certain poisons called ptomaines, which are formed by the bacteria during the process of growth. The disease we call typhoid fever is thus caused. The bacterium causing the fever is taken into the body through the mouth in water, milk, or other food. Once in the intestine the bacteria multiply very rapidly, producing a ptomaine. This poison gets into the blood and is passed to all parts of the
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