156 THE STORY OF GERM LIFE. 



RECOVERY FROM GERM DISEASES. 



These resisting forces are not always sufficient 

 to drive off the invaders. The organisms may 

 retain their hold in the body for a time and 

 eventually break down the resistance. After this 

 they may multiply unimpeded and take entire 

 possession of the body. As they become more 

 numerous their poisonous products increase and 

 begin to produce direct poisoning effects on the 

 body. The incubation period is over and the dis- 

 ease comes on. The disease now runs its course. 

 It becomes commonly more and more severe until 

 a crisis is reached. Then, unless the poisoning is 

 so severe that death occurs, the effects pass away 

 and recovery takes place. 



But why should not a germ disease be always 

 fatal ? If the bacteria thus take possession of the 

 body and can grow there, why do they not always 

 continue to multiply until they produce sufficient 

 poison to destroy the life of the individual ? 

 Such fatal results do, of course, occur, but in by 

 far the larger proportion of cases recovery finally 

 takes place. 



Plainly, the body must have another set of 

 resisting forces which is concerned in the final 

 recovery. Although weakened by the poisoning 

 and suffering from the disease, it does not yield 

 the battle, but somewhat slowly organizes a new 

 attack upon the invaders. For a time the multi- 

 plying bacteria have an unimpeded course and 

 grow rapidly ; but finally their further increase is 

 checked, their vigour impaired, and after this they 

 diminish in numbers and are finally expelled from 

 the body entirely. Of the nature of this new re- 

 sistance but little is yet known. We notice, in 



