393. Practical Points about Poisons. Poisons should never be kept in the same place with medicines or other preparations used in the household. They should always be put in some secure place under lock and key. Never use internally or externally any part of the contents of any package or bottle unless its exact nature is known. If there is the least doubt about the substance, do not assume the least risk, but destroy it at once. Many times the unknown contents of some bottle or package has been carelessly taken and found to be poison.

Careless and stupid people often take, by mistake, with serious, and often fatal, results, poisonous doses of carbolic acid, bed-bug poison, horse-liniment, oxalic acid, and other poisons. A safe rule is to keep all bottles and boxes containing poisonous substances securely bottled or packed, and carefully labeled with the word POISON plainly written in large letters across the label. Fasten the cork of a bottle containing poison to the bottle itself with copper or iron wire twisted into a knot at the top. This is an effective means of preventing any mistakes, especially in the night.

This subject of poisons assumes nowadays great importance, as it is a common custom to keep about stables, workshops, bathrooms, and living rooms generally a more or less formidable array of germicides, disinfectants, horse-liniments, insect-poisons, and other preparations of a similar character. For the most part they contain poisonous ingredients.

Bacteria.

394. Nature Of Bacteria. The word bacteria is the name applied to very low forms of plant life of microscopic size. Thus, if hay be soaked in water for some time, and a few drops of the liquid are examined under a high power of the microscope, the water is found to be swarming with various forms of living vegetable organisms, or bacteria. These microscopic plants belong to the great fungus division, and consist of many varieties, which may be roughly divided into groups, according as they are spherical, rod-like, spiral, or otherwise in shape.

Each plant consists of a mass of protoplasm surrounded by an ill-defined cell wall. The bacteria vary considerably in size. Some of the rod-shaped varieties are from 1/12,000 to 1/8,000 of an inch in length, and average about 1/50,000 of an inch in diameter. It has been calculated that a space of one cubic millimeter would contain 250,000,000 of these minute organisms, and that they would not weigh more than a milligram.

Fig. 168.—Examples of Micro-Organisms called Bacteria. (Drawn from photographs.)