1 84 INFLAMMATORY AND SUPPURATIVE CONDITIONS. 



potatoes it grows well at ordinary temperature, forming a some- 

 what abundant layer of orange colour. In bouillon it produces 

 a uniform turbidity, which afterwards settles to the bottom as 

 an abundant layer, which assumes a brownish-yellow tint. In 

 the various media it renders the reaction acid, and it coagulates 

 but does not peptonise milk, in which it readily grows. The 

 cultures have a somewhat sour odour. 



It has considerable tenacity of life outside the body, cultures 

 in gelatin often being alive after having been kept for several 

 months. It also requires a rather higher temperature to kill it 

 than most spore-free bacteria, viz. 80 C. for half an hour 

 (Liibbert). 



The staphylococcus pyogenes albus is similar in character, 

 with the exception that its growth on all the media is white. The 

 colour of the staphylococcus aureus may become less distinctly 

 yellow after being kept for some time in culture, but it rarely 

 assumes the white colour of the staphylococcus albus, and it has 

 not been found possible to transform the one organism into 

 the other. 



Staphylococcus epidermidis albus (Welch) is, according to its disco verer,. 

 the most common organism inhabiting the skin, occurring not only on its super- 

 ficial parts, but deeper down, in the hair follicles, and the ducts of the seba- 

 ceous and sweat glands, where it is not effected by the most efficient methods 

 of disinfection. Welch regards it as being a "sport 1 ' of staphylococcus py- 

 ogenes albus and possessed of weak pathogenic powers. It is the usual cause 

 of u stitch abscesses," following upon operative measures. Culturally it shows 

 no variations from the phenomena observed with staphylococcus pyogenes 

 albus, excepting that it requires a relatively longer period of time to accomplish 

 the same. It is probably an attenuated variety of the staphylococcus albus. 



The staphylococcus pyogenes citreus, which is less frequently 

 met with, differs in the colours of the cultures being a lemon 

 yellow, and is less virulent than the other two. 



The staphylococcus cereus albus and staphylococcus cereus 

 flavus are of much less importance. They produce a wax-like 

 growth on gelatin without liquefaction; hence their name. 



Streptococcus pyogenes. This organism is a coccus of 

 slightly larger size than the staphylococcus aureus, about I p in 

 diameter, and forms chains which may contain a large number of 

 members, especially when it is growing in fluids (Fig. 67). The 

 chains vary somewhat in length in different specimens, and on 

 this ground varieties have been distinguished, e.g. the strepto- 



