When a substance to be sterilized by heat will not bear so high a temperature, the method of fractional sterilization is employed, the fluid to be sterilized being heated to from 140°F. to 175°F. or to from 69°C. to 80°C., for from 15 to 30 minutes every 3 days or 7 days. The theory is that the adult germs are killed by the first heating and that any spores which develop subsequently are destroyed in their adult state at the next heating. The fluid, meanwhile, must be kept at an even temperature which will encourage the development of any spores it may contain. Even anthrax spores may be killed by 167°F. to 185°F., or 75°C. to 80°C., in a one and four-tenths solution of bicarbonate of soda, in from 8 to 20 minutes. Dry heat is not so efficient as moist heat.
The following are the more important bacteria we meet in surgical conditions:
Staphylococcus pyogenes aureus—a microorganism producing yellow pus.
Staphylococcus pyogenes citreus—a microorganism producing lemon-colored pus.
Staphylococcus pyogenes albus—a microorganism producing white pus.
Streptococcus pyogenes—a streptococcus producing pus. (Erysipelas for example).
Micrococcus gonorrhea—bacillus of Neisser, or gonococcus.
Bacillus pyocyaneous—producing a green pus.
Bacillus coli communis—producing intestinal conditions. (Appendicitis for example).
Bacillus typhosis—Eberth’s bacillus; producing typhoid fever.