148 BACTERIA IN RELATION TO DISEASE 



for instance, the bacterium of glanders, Actinomyces, and Bacillus pyocyaneus, 

 the bacterium of blue or green pus. The most widely distributed and at the 

 same time most harmless form is Staphylococcus pyogenes aureus {Micrococcus 

 pyogenes). It is a chromogenic species that covers agar with an orange- 

 yellow growth, and sometimes imparts a strong yellow tinge to pus (127). 

 The cells are very small, on an average o-8 ju. in diameter, colourless, and 

 non-motile. They lie singly, or in pairs, or in short chains ; more commonly 

 still in little clusters (Fig. 28, a). Besides this orange-yellow form, a paler 

 kind (S. pyogenes citreus) is known, and also a white one (S. p. albus). 

 They are apparently distinct species, and, although having the same proper- 

 ties as 5". aureus, are not so common. In nature the germs are found every- 

 where, so that they would seem to be metatrophic. 



In disease they are most frequent in local suppurative processes, such 

 as acne (inflammation of the sebaceous glands), sycosis (inflammation of the 

 hair follicles), carbuncle, osteomyelitis, periostitis. Garre rubbed a pure 

 culture of S. aureus into his arm, and created thereby a severe carbuncle in 

 which the bacteria multiplied abundantly. If from such local foci the 

 bacteria spread, metastatic abscesses arise in other organs and in the joints, 

 and the condition known as pyaemia results. 



Another common pus bacterium is Streptococcus pyogenes (128). Of 

 this species there are apparently several races very difficult of distinction. 

 Both in the diseased tissues, and in bouillon cultures particularly, it 

 forms long unbranched chains with cells somewhat larger than those of 

 Staphylococcus (Fig. 28,^). The chains result from the planes of division 

 always being parallel to one another. It is regularly present in erysipelas, 

 and in many other pyogenic diseases. It is sometimes associated with 

 Staphylococcus, which it exceeds in virulence. Like this, too, it gives rise to 

 pyaemia and septicaemia if carried abroad by the blood. It is often 

 present in diphtheria and in phthisis, increasing the severity of the malady, 

 which then assumes the character of a mixed infection. In cultures, 

 Streptococcus dies off much sooner than does Staphylococcus, often in a few 

 weeks. This, and the fact that it is less common outside the body, indicate 

 perhaps that it is a strictly parasitic organism. 



The bacterium of gonorrhoea, the so-called Gonococcus (129), is cer- 

 tainly of exclusively paratrophic habit. Its artificial culture is only 

 possible upon blood-serum, all other media, however nourishing, being use- 

 less. Whence the Micrococcus gonorrhoeae (Fig. 28, c) originally comes is 

 not known, for it has never been found in nature, and perishes in a few hours 

 when dried up. But it is a constant associate of the human race, and is 

 transmissible only by contact. Since the temperature minimum is about 

 25 C, and as the cells die within five hours in water, it is evident that a 

 multiplication of the organism in swimming-baths is not possible. There is no 

 danger of infection from this source. The gonococcus occurs in the inflam- 



