BACTERIAL H^EMOLYSINS 217 



of the same species be injected, hsemolysin is formed (" iso- 

 lysin "), but the injection of the animal's own corpuscles 

 does not give rise to hsemolysin, i.e. " autolysin " is not 

 formed. This is obviously a protective mechanism. 



Many bacteria e.g. B. pyocyaneus , B. typhosus, staphy- 

 lococci and streptococci besides other products directly 

 form hsemolysins in the culture, and the haemoglobin 

 staining occurring in septic diseases, etc., is probably 

 partly due to the action of bodies of this nature elaborated 

 by the infecting organisms. These bacterial hsemolysins 

 are, however, substances quite different from the immune 

 hsemolysins obtained by injecting an animal with blood 

 corpuscles. They act directly upon the corpuscles without 

 the intervention of complement. 



Practical Uses of HaBmolysis, etc. 



1. HAEMOLYSIS TEST. 



Some micro-organisms produce non-specific hsemolysins in 

 culture, others do not ; this may constitute a difference between 

 allied organisms. For instance, as a rule true cholera vibrios do 

 not hsemolyse, while many cholera-like vibrios do. The test can 

 be applied in two ways : (a) Defibrinated rabbits' blood may be 

 mixed with melted agar cooled to 45 C. The mixture is poured 

 into Petri dishes, allowed to set, and when cool inoculated with 

 the organism to be tested in such a manner that separate, well- 

 defined colonies are obtained. After twenty-four hours' incuba- 

 tion at 37 C., colonies when hsemolytic are surrounded with a 

 clear, well-defined halo, contrasting sharply with the dark opaque 

 colour of the agar. If blood-agar is not available, a substitute 

 may be devised by smearing some sterile human or rabbits' blood 

 on a sterile agar plate, (b) A young agar culture is emulsified in 

 45 c.c. of physiological salt solution ; 0-1 c.c. of this suspension 

 is mixed in a small tube with 0-9 c.c. of sterile salt solution and 

 one drop of a sterile suspension of well-washed rabbit or other 

 corpuscles. After twelve to twenty-four hours haemolysis will be 

 apparent if the organism forms hsemolysins. 



