Streptococcus erysipelatis, which is the cause of erysipelas in human beings.
Diplococcus pneumoniæ (A. Fränkel) is the cause of pneumonia, and of the epidemic cerebro-spinal meningitis.
Gonococcus (Neisser) is the cause of gonorrhea and inflammation of the eyes.
Pathogenic Rod-Bacteria. Bacterium choleræ gallinarum, an aerobic, facultative parasite which produces fowl-cholera among poultry; it is easily cultivated on various substrata as a saprophyte. The disease may be conveyed both through wounds and by food, and may also be communicated to mammals.
Bacillus anthracis, the Anthrax bacillus (Fig. [32]), chiefly attacks mammals, especially herbivorous animals (house mice, guinea-pigs, rabbits, sheep, cattle), in a less degree omnivorous animals (including human beings), and in a still less degree the Carnivores. Aerobic. Cylindrical cells, 3–4 times as long as broad, united into long rod-like bodies, which may elongate into long, bent, and twisted filaments. Not self-motile. Endosporous. Germination takes place without the throwing off of any spore-membrane (compare Hay-bacillus p. [37] which resembles it). Contagion may take place both by introduction into wounds, and from the mucous membrane of the intestines or lungs, both by vegetative cells and by spores; in intestinal anthrax, however, only by spores. The Bacillus multiplies as soon as it has entered the blood, and the anthrax disease commences. The Bacilli not only give off poison, but also deprive the blood of its oxygen. Vegetative cells only occur in living animals. This species is a facultative parasite which in the first stage is a saprophyte, and only in this condition forms spores.
Fig. 32.—Anthrax bacillus (Bacillus anthracis) with red (b) and white (a) blood-corpuscles.
Fig. 33.—Anthrax bacillus. The formation of the spores; magnified 450 times.
Bacillus tuberculosis produces tuberculosis in human beings, also in domestic animals (perlsucht). It is a distinct parasite, but may also live saprophytically. It is rod-formed, often slightly bent, and is recognised principally by its action with stains (when stained with an alkaline solution of methyl-blue or carbolic fuchsin, it retains the colour for a long time even in solutions of mineral acids, in contrast with the majority of well-known Bacteria): it probably forms spores which are able to resist heat, dryness, etc.