Introduction 



IT IS A, universal phenomenon of nature that every hving form must 

 struggle to perpetuate its existence. In this pursuit its primary energy 

 is spent in the search for food. Its chemical activities determine the 

 extent the food can be made use of. From the standpoint of a free 

 living bacterium, it is immaterial whether it derives its food from dead 

 matter, or within a suitable host; the host is simply another medium 

 for its propagation. The disease, death, and immunity, in case of 

 recovery, caused by its multiplication in a host, are incidental events. 

 Only extremely parasitic living forms are dependent on a host. The 

 focus of our interest must of necessity be the nature and the intensity 

 of the chemical activities of micro-organisms, for these constitute their 

 biologically indispensable characteristics and determine the nature and 

 the fatality of the diseases they cause. 



Micro-organisms of varying degrees of virulence, such as Group 

 A /^-hemolytic streftococci, Stre^ptococcus viridans, fneumococcus, Sal- 

 monella aerlrycke, C. difhtheriae, Shigella dysenteriae, CI. tetani, CI. 

 hotulinum, CI. welchii, Stafhylococcus aureus, B. fwteus, members of 

 the colon group, etc., produce their exotoxins and endotoxins in vitro 

 under special or routine laboratory growth conditions. It is immaterial 

 how these toxins are produced; whether they are products of bacterial 

 secretion, autolysis, or a result of the activities of certain specific bac- 

 terial enzymes on the medium, or are extracted from the intact cell by 

 chemical manipulation, has no bearing on the basic aspect of the 

 question. As these poisons can be elaborated by the bacteria outside of, 

 or in the body of hosts, they are the products of their specific physio- 

 logical activities in the course of their normal growth and death. 



Many of the pathogenic bacteria produce acute exotoxic diseases. 

 However, in chronic infections, the disease agents either do not elabo- 

 rate such fatal poisons, or they are rendered less harmful by the host. 

 Whatever may be the answer, at the end a serious condition may 

 develop to a greater or lesser degree as the result of the physiological 



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