l^HE ORGANISMS OF SUPPURATION. 177 



COCCUS pyogenes. It may as well be mentioned here 

 that no differences sufficiently important to distinguish 

 them from one another have as yet been discovered 

 between the streptococcus of' suppuration and that of 

 erysipelas. They are similar morphologically, and 

 also in their behaviour in cultivations and in staining 

 solutions. Ifc is therefore best to class them together, 

 especially as recent observations on their pathogenic 

 behaviour support this view, and to consider that the 

 slight differences which can be observed between 

 them are caused by their mode of invasion or by 

 physiological variations due to external conditions. 

 We are most sure to find the Streptococcus pyogenes 

 in pus which has been taken from wounds, where 

 extensive inflammation along the course of the 

 lymphatics has occurred. We take a small portion 

 of this pus, and prepare plate cultures with it just as 

 we did with the pus containing the Staphylococcus 

 pyogenes. The colonies develop more slowly than 

 those of the latter; in the interior of the gelatine 

 fchey form small whibish points, scarcely as large as 

 pins' heads, and on the surface thin colourless films. 

 Even after having been kept for some time, the 

 appearance of the cultures is not much changed ; the 

 colonies grow no larger, and, even after months, the 

 gelatine has not commenced to liquefy. If a puncture 

 cultivation is made in gelatine, and is kept at a tem- 

 perature of about 22° C, after about eight days the 



