CHAPTER XVI. 



A. GENERAL PROPERTIES OF BACTERICIDAL 

 SERUMS. 



Antibacterial, bactericidal and bacteriolytic are 

 three terms which are used in a rather loose, inter- 

 changeable way, although they are not strictly 

 synonymous. A bactericidal serum is one which is 

 able to kill bacteria, as the term implies ; if at the 

 same time it dissolves the organisms it is bacterio- 

 lytic. Inasmuch as some serums, as antityphoid, 

 do kill bacteria without dissolving them, while 

 others, as anticholera, have the dissolving power, 

 the distinction has a certain significance. In either 

 case the serum is, of course, antibacterial. For 

 lack of a more concise English term, bacteriolysis 

 is used to designate the process in which bacteria, 

 with or without solution, are killed by serums. 

 Bacteriolysin refers to the substances in serum 

 which accomplish this action. The means of de- 

 termining the bactericidal power of a serum are 

 indicated on page 254. True bacteriolysis is best 

 observed with the organism of cholera and its 

 antiserum as described later under the title of the 

 Pfeiffer experiment. 



Bacteriolysins are far more complex than anti- 

 toxins, agglutinins and precipitins. One may best 

 appreciate their nature as understood at present 

 by tracing their development from the relatively 

 simple alexins of Buchner. 



Following the investigations of Fodor, Behring Alexius 

 and others, which showed that normal blood may 



