158 The Story of the Bacteria 



well on the way toward understanding the 

 nature of acquired immunity. They must 

 be in some way different from their fellows 

 and must have either acquired some new 

 qualities which they did not possess before 

 their disease adventure, or old protective 

 agencies must have been reinforced. 



How light has been thrown, little by little, 

 on this important subject by the busy self- 

 sacrificing workers, both in the laboratory 

 and at the bedside, makes an interesting 

 story which we cannot now stop to tell. But 

 the fact is, that when certain poisons, espe- 

 cially those formed by bacteria, get into the 

 body, some of the body cells proceed forth- 

 with to make and set free chemical substances 

 which unite with the poisons, changing their 

 character and making them harmless. 

 Through this action of his cells, the recovering 

 victim of an infection destroys the poisons as 

 they are made. The bacteria which make 

 the poisons are thus robbed of their chief 

 significance and do not particularly concern 

 the patient any further. So he gets well. 

 But something more may happen. His cells, 



