THE RELATION OF BACTKHIA Tn Dlsi: \ j.- 



especially from the streptococcus, pneurnococcus, and staphylococcus ; 

 but nearly all forms of bacteria, when they accumulate in one 

 locality, may produce purulent inflammation. The colon, typhoid, 

 and influenza bacilli frequently cause the formation of abscesses. 



Catarrhal inflammation, with or without pus, follows the absorption 

 of the products of many bacteria, such as the gonococcus, pneumo- 

 coccus, streptococcus, and influenza bacillus, etc. The hemorrhagic 

 exudation seen in pneumonia is usually due to the pneumococcus ; it is 

 observed also in other infections. Cell necrosis is produced frequently 

 by the products of the diphtheria and of the typhoid bacilli and by 

 those of other bacteria. Specific proliferative inflammation follows 

 the localization of the products derived from the tubercle bacillus and 

 the leprosy bacillus. 



Not only can the poisons of one species of bacteria, according to the 

 tissues attacked, produce several forms of inflammation, but the same 

 organism will vary as to its mode and extent of invasion; this depend- 

 ing, first, upon its own characteristics at the time as to virulence, etc., 

 and, second, upon the conditions in the infected animal, such as its 

 health and power of resistance, the location of infection, and the cir- 

 cumstances under which the animal remains. Such variations, there- 

 fore, are in no case specific, for different poisons will produce changes 

 which appear identical. >, 



Manner in which Bacteria Produce Injury. The actual mechanical 

 presence of the bacteria is only of importance when, as in pronounced 

 septicaemia or pyaemia, they exist in such enormous numbers as to inter- 

 fere mechanically with the circulation or cause minute thrombi, and 

 later emboli, which finally produce infarction and abscesses in different 

 parts of the body. Even these dangerous effects are almost wholly 

 due to the chemical substances given off, which are more or less directly 

 poisonous. Some portion of the protoplasm of almost every variety 

 of bacteria acts as an irritant to tissues and combines with some of 

 the body cells, and that of most have a positive chemotaxis. 



These poisonous products, as already described in the previous 

 chapter, can be separated from the culture fluid in which the bacteria 

 have grown or they can be extracted from their bodies. These prod- 

 ucts without the bacteria themselves injected into animals cause essen- 

 tially the same lesions as are produced by the bacteria when they develop 

 in the animal body. The substances contained in or produced by the 

 bacteria, with few exceptions, attract the leukocytes, and when great 

 masses of bacteria die suppuration usually follows. 



General Symptoms Caused by Bacterial Poisons Absorbed into the Circu- 

 lation. Fever is produced under favorable conditions by all bacterial 

 poisons. The first requisite is that sufficient poisons be absorbed; but, 

 on the other hand, they must not be absorbed with such rapidity as 

 to overwhelm the infected, for a moderate dose may raise the tem- 

 perature, while a very large dose lowers it, as occurs sometimes when 

 a very large surface, such as the peritoneum, is suddenly involved. The 

 effect of fever has no known antibacterial power, but it may be due to 



10 



