62 ESSAYS ON BACTERIOLOGY. 



successfully used to cure infected swine. He claims, 

 says Ernst, that' he has by these experiments entered 

 upon the first stage of a certain and rational treatment 

 of infectious disease, and urges it to be the duty of all 

 to strive for the attainment of an ideal that must com- 

 plete the discovery and manufacture of the true anti- 

 bacterial material. The time is pei'liaps not far dis- 

 tant when such a material will be in the hands of all 

 who are called on to treat infectious diseases. Otber 

 diseases besides swine fever are already under investi- 

 gation. It v/ill be noted by the study of this whole 

 matter that the tendency now is to use the natural 

 laboratory, that is, the living body, rather than arti- 

 ficial cultures to secure these protective agents. 



In Slimming up this matter, in order to indicate the 

 present statiis of the contest against infection, I make 

 the following brief statement as an indication of the 

 best present opinion: 



First. The infectious diseases are due to living 

 agents. 



Second. Bacteria injure the body and cause sick- 

 ness through the production of poisonous substances 

 called, loosely, ptomaines or toxins. 



Third. Self -limitation and immunity are in some 

 way, directly or indirectly, brought about by the ac- 

 tion of such chemical substances, the protective 

 agents, however, not being necessarily the same as 

 those which cause the sickness. 



Fourth. These protective agents may be found in 

 the blood serum and body juices. 



