68 THE STORY OF THE BACTERIA. 



It sometimes happens that so extensive a 

 growth of the bacteria occurs in some local 

 region of the body and so much of the soluble 

 poison is produced that although the bacteria 

 may not themselves get generally distributed 

 the poison which they furnish may enter the 

 circulation, and so produce in distant parts of 

 the body most serious disturbance or even 

 cause death. These bacteria apparently do no 

 harm when they lodge upon the uninjured sur- 

 face of the body, but only when they get into 

 the tissues through an injury or lodge upon sur- 

 faces of the respiratory or digestive tract which 

 are already the seat of disease. 



This is in brief the story of the bacteria 

 which most commonly produce the common 

 inflammations of the tissues, the complications 

 in the healing of wounds, and the varying 

 phases of blood poisoning. As pus in greater 

 or less quantity is apt to be produced under 

 these circumstances, these bacteria are called 

 the pus-forming or pyogenic bacteria. Some 

 other bacteria may occasionally produce simi- 

 lar effects, but those which have been described 

 are the most common and important. 



