LOCALIZED INFECTIONS OF PUS NATURE 87 



in relation to the defence, just so there are greater 

 eft'ects in the production of infection. In increasing 

 severity there are the following grades: 



Abscess is a local collection of pus in which the 

 resistance put up by the tissue prevents the inflamma- 





FIG. 25. Secondary infection of a glomerulus of kidney by the 

 Staphylococcus aureus in a case of ulcerative endocarditis. The 

 cocci (stained doubly) are seen plugging the capillaries and also 

 lying free. X 300. (Muir and Ritchie.) 



tion from spreading, thus keeping it in a limited space. 

 There is some effect on the general body by absorption 

 of a few bacteria or their poisons, but a densely packed 

 zone of leukocytes around the pus keeps it from gen- 

 eral invasion. Should this barrier be broken or the 

 resistance be too low to hold the invaders a spread of 



