160 THE STORY OF GERM LIFE. 



in method of attack, and in the part ot the body 

 which they seize upon as a nucleus for growth. 

 They differ in violence and in the character of the 

 poisons they produce, as well as in their power of 

 overcoming the resisting powers of the body. 

 They differ at different times in their powers of 

 producing disease. In short, they show such a 

 large number of different methods of action that 

 no general statements can be made which will ap- 

 ply universally, and no one method of guarding 

 against them or in driving them off can be hoped 

 to apply to any extended list of diseases. 



DISEASES CAUSED BY OTHER ORGANISMS THAN 

 BACTERIA. 



Although the purpose of this work is to deal 

 primarily with the bacterial world, it would hardly 

 be fitting to leave the subject without some refer- 

 ence to diseases caused by organisms which do 

 not belong to the group of bacteria. While most 

 of the so-called germ diseases are caused by the 

 bacteria which we have been studying in the 

 previous chapters, there are some whose inciting 

 cause is to be found among organisms belonging 

 to other groups. Some of these are plants of a 

 higher organization than bacteria, but others are 

 undoubtedly microscopic animals. Their life 

 habits are somewhat different from those of 

 bacteria, and hence the course of the diseases is 

 commonly different. Of the diseases thus pro- 

 duced by microscopic animals or by higher plants, 

 one or two are of importance enough to deserve 

 special mention here. 



Malaria. The most important of these dis- 

 eases is malaria in its various forms, and known 



