78 LOCALIZED INFECTIONS OF PUS NATURE 



nal operation, they may penetrate to the interior 

 and cause a peritonitis. Still, again, pus germs may 

 make their entrance in the ways first cited, but cause 

 no trouble at the site of entrance, being carried hence 

 by the blood stream to cause trouble at other places. 

 Any reaction set up by bacteria is called inflammation, 

 and in no other 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 inflammation, but to explain 

 the physical expressions of inflammation 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 

 defense or the bacterial attack. If the former exceeds 

 the latter the part assumes its normal character after 

 a brief time. As the infecting forces become greater 

 in relation to the defense, just so there are greater 



