MANUAL OF BACTERIOLOGY. 



persons rarely die of the disease with which they suffer. 

 Secondary infections, or, as we are apt to call them in 

 hospital work, terminal infections, carry off many of the 

 incurable cases in the wards." 



The term secondary infection is also used for the modifi- 

 cation of an infectious process which has been in existence 

 for some time, by infection with a second variety of bacte- 

 ria. That takes place, for instance, in pulmonary tubercu- 

 losis, when the invasion of the already tuberculous lungs by 

 the pyogenic micrococci assists in the formation of cavities. 

 In this sense it will be seen that the term secondary infec- 

 tion is used as a name for a variety of mixed infection. In 

 the secondary, mixed and terminal infections, the bacteria 

 which enter secondarily are likely to be of the pus-producing 

 varieties, especially the streptococcus pyogenes. 



As to the mechanism which bacteria make use of in 

 order to produce disease, according to our present knowl- 

 edge, they work chiefly through the poisonous substances 

 formed by them and deposited in the bodies of the persons 

 suffering from the disease. The theory that bacteria have 

 an important influence through the destruction of substances 

 taken by them from the body of the patient for food, is no 

 longer entitled to much weight; neither are we able in most 

 cases to account for the phenomena of disease by any 

 mechanical action on the part of the bodies of bacteria. 

 That such action does occasionally take place may be seen 

 in experimental anthrax in mice, where the blood-capil- 

 laries of the liver and kidneys may be completely plugged 

 with masses of anthrax bacilli. The diseases in which 

 the circulating blood is swarming with bacteria are much 

 commoner in the lower animals than in man. 



Toxemia. By toxemia is meant the absorption of poison- 

 ous bacterial products from a localized point of invasion, 

 and their dissemination throughout the body by means of 



