Bacteria / Especially as they are related to the economy of nature, to industrial processes, and to the public health

by Sir George Newman

2. The bacteria serving as test objects should have equal power of resistance.

3. The numbers of bacteria used in comparative observation should be approximately equal.

4. The disinfecting solution must be always used at the same temperature in comparative experiments.

5. The bacteria must be brought into contact with the disinfectant with as little as possible of the nutrient material carried over. (This obviously will depend upon the object of the research.)

6. After having been exposed to the disinfectant for a fixed time, they should be freed from it as far as possible.

7. They should then be returned in equal numbers to the respective culture medium most favourable to the development of each, and kept at the same, preferably the optimum, temperature for their growth.

8. The number of surviving bacteria capable of giving rise to colonies in solid media must be estimated after the lapse of equal periods of time.

We may now turn from general principles to mention shortly some of the commoner methods and substances adopted to secure efficient disinfection. They are all divisible, according to Sir George Buchanan's standard, into two groups:

1. Heat in various forms;