348 INFECTION AND RESISTANCE 



Such cases of septicemia, however, are not in our opinion the 

 most common ones in the human being. It is probable that all 

 localized infections of more than a very trifling nature discharge 

 living bacteria into the circulation from the very beginning. How- 

 ever, in most cases the bacteria, though able to hold their own in 

 their entrenched position at the focus where accumulated offensive 

 factors and local injury reenforce them, are yet rapidly destroyed 

 when, in small detachments, they get into the open circulation where 

 the plasma antibodies and phagocytes are freely active. There are 

 cases which take a middle course between such purely localized 

 lesions and the acute septicemia, conditions in which a well-estab- 

 lished focus continues to furnish bacteria to the blood stream as fast 

 as they are destroyed. An example which illustrates our meaning 

 well is that of the so-called subacute endocarditis caused by the 

 Streptococcus viridans and its close biological kin, where blood cul- 

 tures are often consistently positive for a long period or may show 

 occasional intervals in which the blood is bacteria-free. The focus 

 on the heart valves apparently can continue uncured in spite of a 

 relatively high or at least normal systemic resistance to the micro- 

 organisms. If, as we ourselves have done, we isolate the organisms 

 by blood culture from such cases, and then measure the opsonic prop- 

 erties of the patient's own serum against them, using the patient's 

 own leukocytes, we may often find that active phagocytosis takes 

 place, in a degree equal or even superior to that taking place in the 

 serum of normal individuals. Neither does there seem to be a dimin- 

 ished phagocytic power of the patient's own leukocytes. For a long 

 time these conditions may continue, with a constant destruction of 

 bacteria in the blood and a corresponding renewal of the supply from 

 the lesion. The same condition can be observed in rabbits in which 

 chronic endocarditis with persistently positive blood culture has been 

 produced by injections of these bacteria. In such animals measure- 

 ments similar to those described above have been made by Miss Gil- 

 bert in our laboratory, and it has seemed as though persistently 

 positive blood cultures could be obtained only when a localized focus 

 was set up in the animals. Unless this is the case the blood cultures 

 rapidly become negative. 



Conditions essentially similar may exist in any ' other form of 

 severe localized infection. Positive blood cultures do not necessarily 

 mean a multiplication of the bacteria in the blood stream and a rapid 

 overwhelming of the body. We have had occasion to see a number of 

 cases of bacteriemia in which the focus of infection was surgically 

 accessible ; and in some of these cases early removal of the focus an( 

 purely surgical treatment resulted in a clearing up of the infection 

 Similar experiences have been reported by Libman and a number of 

 others, and for this reason general septicemia, if not fulminating, 

 may still be less desperate than ordinarily supposed. 



