Micrococci are to be found virtually in all abscesses or suppurations, and the form now under consideration is the most important. It has been studied by many authors, of whom Ogston, who suggested the term staphylococcus (from , a bunch of grapes), and Kosenbach, who gave the full name, may be mentioned.
It is smaller than the coccus of erysipelas, and in its growth tends to form little masses rather than chains (Fig. 138). It is not known to produce spores, but it is peculiarly resistant to drying and heat.
Fig. 138. - Staphylococcus pyogenes aureus, x about 1000.
Fig. 139. - Streptococcus pyogenes, x about 1000.
It may be kept dry on a cover glass for ten days without losing its power, and it requires the temperature of boiling water for several minutes in order to kill it.
It grows at the ordinary temperature, but more vigorously at higher degrees. It grows on gelatine, agar-agar, and potato, forming in all of them bright orange-coloured masses, which have been aptly compared to layers of oil paint. It rapidly liquefies gelatine.
Suppurative inflammations have been frequently produced by the artificial application of this bacterium. Garre applied it to his own person, once to a fissure at the finger-nail, and once by rubbing into his forearm. In the former case he produced a spreading suppuration, and in the latter a considerable carbuncle, which took weeks to heal.
The relation of this microbe to acute infective ostitis and to ulcerative endocarditis is very interesting. If large quantities of the culture be injected into animals they will die of poisoning in a short time, but if small quantities be used they will usually recover. However, an injury to the valves of the heart on the one hand, or to a bone on the other, will determine the settlement of the cocci in one or other of these situations, the result' being a malignant infective inflammation. (See under Ulcerative Endocarditis, and Suppurative Ostitis).
Abscesses may be produced in animals by the subcutaneous injection of cultures of this microbe. Acute peritonitis is produced by injection into the abdomen, and acute synovitis by injection into the joints.
This micrococcus is very widely distributed, occurring in almost all suppurations, but also in the normal saliva, in water, and air. All open wounds are exposed to its inroads, and it will depend somewhat on circumstances whether it penetrate further inwards.