. Laboratory work in bacteriology. Bacteriology. OBSEEVATION OF INFECTED ANIMALS. 273 numbered and designated by their color, by their curly or smooth hair, etc., and, if need be, by painting the nose, back or flank with anilin dyes. The student should never burden his memory with details as to dose, time of inocula- tion, etc. A complete record should be made at the time the work is done, and in this way all uncertainty is done away with. The experimental animals, as a rule, should be weighed before infection, and every day or two afterward. Each weighing should be done, as nearly as possible
. Laboratory work in bacteriology. Bacteriology. OBSEEVATION OF INFECTED ANIMALS. 273 numbered and designated by their color, by their curly or smooth hair, etc., and, if need be, by painting the nose, back or flank with anilin dyes. The student should never burden his memory with details as to dose, time of inocula- tion, etc. A complete record should be made at the time the work is done, and in this way all uncertainty is done away with. The experimental animals, as a rule, should be weighed before infection, and every day or two afterward. Each weighing should be done, as nearly as possible, under the same conditions as the first one. That is to say, the animal should have plenty of ,food and water before weighing. In warm weather the need of water is especially imperative. An experimental animal may show a difference of 200 or 300 g. between the two weighings, and this differ- ence may be wholly due to the with- holding of water. Unless the precau- tions mentioned are observed the weighing results will have no value whatsoever. When properly carried out, it affords the best possible index of the physical well-being of the animal. A steady, though slight decrease in weight, is a sure indication of a chronic, wasting disease. On the other hand, a steady increase in weight is, as a rule, a reliable index of health. The temperature of the animal should be taken before beginning the experiment, and subsequently on each suc- cessive day at the same hour. The ordinary clinical ther- mometer should be inserted well up into the rectum. Pre- vious to insertion, the bulb should be covered with vaselin. The variations in temperature are especially important, when studying the action of bacterial poisons on the animal Fig. 46. a—Rat cage with leaded, wire-gauze top; iJ—Rat or crucible Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustration
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