138 WARFARE IN THE HUMAN BODY 



There must be activating catalysts. If that is so blood 

 may not be truly bactericidal until it is invaded, and only 

 then if it is healthy, i.e. if it possesses normal powers of 

 reaction. Such views account for the high mortality 

 among the very healthy in some disorders, while the sickly 

 person who is, perhaps, half-poisoned by an excess of many 

 provoked catalysts is prepared, at least partially, for any 

 kind of invasion. The organism, too, has to deal with, 

 destroy, or utilize its own products. Each organ must 

 deal with its own excreta, with the excreta of its neighbour 

 colonies, and for these purposes reacts on their stimula- 

 tion. Its reactions with invaders must employ like 

 machinery. Life itself depends on immunization which is 

 active warfare. 



Immunity, however, does not always seem to be merely 

 a matter of the increase of the blood's bactericidal qualities, 

 to whatever catalysts that may be due, but to local con- 

 ditions. How else can relapses be explained ? For 

 instance, there are the relapses of typhoid fever. When the 

 fastigium has been reached and passed, and when on any 

 theory a defence should have been acquired, the tempera- 

 ture again rises, and there is another attack. In the same 

 way a catarrh of the lungs may disappear after a due 

 reaction period, and another patch will occur. Such facts, 

 though they do not negative the ordinary views of im- 

 munity suggested above, at least show that prolonged 

 febrile reactions do not always produce complete temporary 

 immunity : the most probable explanation being that the 

 local lesions in these cases are external, as the bowel, 

 say, in typhoid is properly external, and are with diffi- 

 culty exposed to the immunizing agents, owing to local 

 swellings and stasis, or to the incomplete response of the 

 weakened organism in the production of the combining 



