184 MANUAL OF BACTERIOLOGY. 



mixed and terminal infections, the bacteria which enter second- 

 arily 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 knowledge, 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 in- 

 fluence through the destruction of substances taken by them 

 from the bcdy 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 occa- 

 sionally take place may be seen in experimental anthrax in 

 mice, where the blccd-capillaries 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 ment the absorption of poisonous 

 bacterial products from a localized point of invasion, and their 

 dissemination throughout the body by means of the circulation. 

 We see typical toxemias in diphtheria and tetanus. In surgery 

 the term sapremia is used to cover a similar condition of affairs 

 when the absorption proceeds from a wound or denuded sur- 

 face, as may happen in the puerperal uterus. 



Septicemia. — In septicemia there is not only absorption 

 of bacterial poisons, but an invasion by bacteria of the living 

 tissues and the blood. The presence of large numbers of 

 bacteria disseminated throughout the body and in the blood is 

 less common in septicemia in man than in such diseases as 

 anthrax in the lower animals. Typical septicemias in man 

 are found in relapsing fever. and certain cases of bubonic 

 plague. For pyemia, see the article on Suppuration, Part IV. 



The principal agencies in effecting recovery from infectious 



