40 BACTERIOLOGY 



In other instances a parasitic species may manifest its 

 activities in a very insignificant way, insofar as the welfare 

 of the host is concerned. The causation of simple boils, 

 pimples and unimportant local inflammations serves to 

 illustrate this. In other examples we find the activities 

 of the parasite more or less confined to special vital organs 

 of the body, the restriction, practically speaking, of the 

 cholera and dysentery germs to the mucosa of the intestinal 

 canal; of the gonorrheal germ to the mucous surfaces of 

 the genito-urinary tract; of ■ the typhoid bacillus to the 

 lymphatic structures of the abdominal cavity may serve 

 as illustrations. 



Again we know of parasitic species that do not disseminate 

 beyond their portal of entry. They grow at that point and 

 manufacture deadly poisons which are disseminated through- 

 out the body by way of the circulating fluids. The germs 

 of diphtheria and of tetanus are striking illustrations of 

 this type of parasite. 



In practically all cases fever is an accompaniment of the 

 activities of the parasitic bacteria in the body though in 

 certain particular instances an initial rise in temperature 

 may be followed by marked depressions of it, due to the 

 action of the poisons elaborated by the bacteria. 



In considering the activities of the parasitic group of 

 bacteria we encounter at the beginning one factor in par- 

 ticular with which we are not called upon to reckon in speak- 

 ing of the saprophytic group. The saprophytes work upon 

 inert, dead matter; the parasites on active, living matter, 

 all of which is by nature endowed with some degree of 

 resistance to the inroads and activities of invading para- 

 sites. It is through this " vital resistance" possessed by the 

 living host that many of the irregularities seen in the opera- 



