SUPPURATION 313 



cultured in fluid media (hence S. longus and S. brews). They 

 multiply by direct division of the individual elements, and in old 

 cultures it has been observed that the cocci vary in form and size 

 (involution forms). This latter fact gave support to the theory that 

 streptococcus reproduced itself by arthrospores, or " mother-cells." 



In culture upon the ordinary media, Streptococcus pyogenes is com- 

 paratively slow-growing, producing minute white colonies on or / 

 about the sixth day. It does not liquefy gelatine, and remains 

 strictly localised to the track of the inoculating needle. Like the 

 staphylococcus, it readily loses virulence. The thermal death-point 

 is, however, lower, being 54 C. for ten minutes. Marmorek has 

 devised a method by which the virulence may be greatly increased, 

 and he holds that it depends upon the degree of virulence possessed 

 by any particular streptococcus as to what effects it will produce. 

 By the adoption of Marmorek's methods, attempts have been made to 

 prepare an antitoxin. 



Streptococcus pyogenes has been isolated from the membrane in 

 cases of diphtheria, and from small-pox, scarlet fever, vaccinia, and 

 other diseases. In such cases it is probably not the causal agent, but 

 merely associated with the complications of these diseases. Suppura- 

 tion and erysipelas are the only pathological conditions in which the 

 causal agency of Streptococcus has been sufficiently established. 



3. The Bacillus pyocyaneus occurs in green pus, and is the cause 

 of the coloration. G-essard was the first to prove its significance, 

 and he described two varieties. It is a minute, actively motile, non- 

 sporulating bacillus, which occasionally complicates suppuration and 

 produces blue-green pus. It stains with the ordinary aniline stains, 

 but is decolorised by Gram's method. Oxygen is necessary for 

 pigmentation, which is due to two substances : pyocyanin, a greenish- 

 blue product extracted with chloroform, and pyoxantJiosc, a brown 

 substance derived from the oxidation of the former pigment. Both 

 these colours are produced in cultivation outside the body. On 

 gelatine the colour produced is green, passing on to olive. There is 

 liquefaction. On potato we generally obtain a brown growth (com- 

 pare B. coli, B. mallei, and others). The .. ,. 

 organism grows rapidly on all the ordinary ::/ "*lg* Jf 

 media, which it has a tendency to colour u ** 

 throughout. It- will be remembered that "* /, ' 



when speaking of the antagonism of organ- /f 



isms, we referred to the inimical action of 



B. pyocyaneus upon the bacillus of anthrax. ft ^ 



4. MicrOCOCCUS tetragonUS. This Species FIG. 26. Diagram of Micrococcus 



occurs in phthisical cavities, and in certain 



suppurations in the region of the face. The micrococcus usually 



occurs in the form of small tetrads. A capsule is generally present. 



