CHAPTER XVII 

 BACTERIA IN RELATION TO DISEASE (Continued} 



3. Mode of Action of Bacteria, and the Reaction of the Organism. 

 Serum Therapeutics and Immunity. 



WHEN bacteria by one means or another have obtained entrance into 

 the body, there elapses before the outbreak of the disease a certain interval, 

 the period of incubation. In the guinea-pig, after infection with Strepto- 

 cocci, from fifteen to sixty hours pass before symptoms begin ; after infection 

 with cholera germs, from one to three days ; in human beings the period of 

 incubation for anthrax is three to seven days, for syphilis, three to four 

 weeks, for rabies forty days or more. During this time the invading bac- 

 teria are multiplying and struggling for mastery with the invaded organism. 

 The struggle may go on without any outward signs at all, or it may be 

 accompanied by slight disturbances of health. If the tissues conquer at the 

 very commencement, the disease never breaks out. It is quite possible that 

 many a temporary indisposition and fleeting local pain may be the expres- 

 sion of such a conflict, in which the defeat of the bacteria prevents the onset 

 of grave illness, for it is certain that pathogenic bacteria enter the body far 

 more often than the number of actual illnesses we are subject to would lead 

 us to suppose. 



But if the first attempts at defence on the part of the body are 

 futile, and the bacteria are able to multiply, then the disease breaks out 

 and severe symptoms show that the struggle between host and parasite has 

 become more intense. Of these symptoms it is now no longer possible to 

 say which are measures of defence on the part of the tissues, and which are 

 signs of defeat. 



A weakening of the body through the abstraction of nutriment by the 

 bacteria is hardly possible, for the micro-organisms, even when multiplying 



