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the characteristic golden yellow pigment. Upon the surface of agar, spherical colonies are formed which acquire an orange tint. Milk is rapidly coagulated, with the formation of lactic and butyric acids.
It has been shown that a weakened culture of the "golden staphylococcus " suddenly becomes virulent on the addition of a certain amount of grape sugar. This probably explains why boils are so frequently observed among those engaged in sugar refining. The carbuncles
Fig. 6.—A, Staphylococcus Pyogenes Aureus. B, Streptococcus
[From Curtis's Essentials of Practical Bacteriology.] associated with glycosuria are, however, due to the lowered vitality of the tissues, which can no longer prevent the development of the pyogenic cocci normally present on the skin.
The pyogenic properties of this micrococcus can be easily demonstrated by rubbing a pure culture on the skin; or by subcutaneous injection in a rabbit or a guinea-pig. In fatal cases the most characteristic changes are observed in the kidneys, the capillaries of which are
plugged up with the micrococci. Metastatic abscesses may also be found.
Streptococcus Pyogenes.--This organism is found in acute abscesses, puerperal fever, ulcerative endocarditis, and (associated with the specific bacilli) in the diphtheritic false membrane, and, in fact, everywhere where there is suppuration. It is also frequently met with in the mouth and nose of healthy individuals. There is reason to believe that the so-called streptococcus erysipelatis is not a distinct species, but merely a variety of the streptococcus pyogenes.
Under the microscope the organism is seen to consist of spherical cocci arranged in pairs or in the form of a chain. In gelatine stab cultures numerous small white colonies are formed without any liquefaction of the medium. In blood serum the colonies readily appear in the form of minute white dots. Milk is slowly coagulated.
Injected subcutaneously, the streptococcus may set up a localised erysipelatous inflammation, the organisms being found in the lymphatic vessels and spaces at the spreading margin of the inflamed area. The subcutaneous tissue elements are not peptonised and broken down into pus, as in the case of the staphylococci. Should the cocci find their way into the cellular tissue, a cellulitis is produced, and if they enter into the circulation à septicæmia or pyæmia may follow.
The nature of the toxins secreted by the organism is not known. But horses have been successfully immunised against infection by repeated injections of sublethal doses of the living virus. The blood serum of these animals constitutes the anti-streptococcus serum ; and has been extensively employed in those infections which are due to the streptococcus pyogenes.
Oriental Sore. This is the name applied to a circumscribed inflammation of the skin that occurs endemically in Delhi, Lahore, Bagdad, and other places in the Eastern hemisphere. It begins as a papule, which sooner or later breaks down into an ulcer, and finally cicatrises. It is auto-inoculable ; and can, moreover, be communicated to lower animals by the inoculation of discharges from the surface of the ulcer. The specific germ has not yet been isolated ; but recent researches show that it is of the nature of streptococcus. As a rule second attacks do not occur.
It may be taken as established that the gonococcus of Neisser is the essential cause of gonorrhea. When the gonorrhæal pus is stained with methylene blue, and examined under the microscope, the specific organisms are seen to be kidney-shaped, or like coffee beans. They
Fig. 7.-Gonococci from the Urethral Secretion.
[From Schenk's Bacteriology.]
are usually arranged in pairs, with the concave surfaces adjacent to each other. An important feature is the frequent presence of the cocci in the interior of the pus cells, where they may be found in considerable numbers. Another important point is that the organisms are not stained by Gram's method, i.e., they are decolorised by alcohol, after having been treated with an aniline dye, and the iodine solution employed in Gram's method of staining (p. 133).
Unlike other diplococci which may be present in the pus, the gonococcus refuses to grow on ordinary media, unless human serum is present at the same time. Bloodagar, or a mixture of fluid agar with albuminous urine, gives satisfactory results.
The gonococcus has only a slight resistance, the specific pus being rendered innocuous by exposure to 60° C. for ten minutes.
The ordinary laboratory animals are immune to gonorrhoea ; but the disease can be reproduced in man by inoculating the healthy urethra with the gonorrhoeal pus.