80 LOCALIZED INFECTIONS OF PUS NATURE 

 conditions is this so well illustrated as in the effects of "pus 



cocci." 



Inflammation. Inflammation is the reaction on the part 

 of the body to the presence of bacteria themselves or to their 

 products. It is expressed by swelling, increased heat, redness, 

 pain, and some loss of function. It is not worth while to go 

 deeply into what may be seen under the microscope in inflam- 

 mation, but to explain the physical expressions of inflamma- 

 tion just given a few lines seems advisable. The swelling, 

 heat, and redness are due to an increase of the blood in the 

 affected part, called forth by forces exerted by the bacteria. 

 These are protective phenomena whereby the body sends an 

 excess of its most potent protective tissue, the blood, to stop 

 the onslaught of microorganisms. The forces exerted by 

 the invaders attract the white cells of the blood, which collect 

 about the outsiders and try to destroy them. The pain is 

 due to the irritation of the fine nerves of the part, and loss 

 of function can be explained by a combination of all the 

 other features of inflammation. The further course of this 

 reaction depends upon which force is the stronger, the body 

 defence or the bacterial attack. If the former exceed the 

 latter the part assumes its normal character after a brief 

 time. As the infecting forces become greater in relation to 

 the defence, just so there are greater effects 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 inflammation from spread- 

 ing, 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 general invasion. Should this barrier be 

 broken or the resistance be too low to hold the invaders a 

 spread of the pus occurs and cellulitis or phlegmon arises. 

 The next grade of severity would be septicemia or pyemia, 

 defined before, which arises when the active inflammation 



