BACTERIOLOGY IN A NUTSHELL. 



with that of the mixed blood of a number of 

 normal persons. The degree of opsonic power 

 as determined by this method has been termed 

 the opsonic index. 



Suppose a patient is suffering with an in- 

 fectious disease like tuberculosis, acne, or ulcer- 

 ative endocarditis. In such conditions why- 

 are the leucocytes unable to prevail in their 

 battle with the invading germs ? It is because 

 the opsonic index is below normal or those sub- 

 stances which enable the leucocytes to fight the 

 germs are diminished. The problem therefore 

 naturally presents itself : increase the opsonins, 

 raise the opsonic index to normal or above 

 normal and the defenders will prevail! 



For obvious reasons any description of 

 laboratory processes in a paper of this kind is 

 entirely out of place, but the practical applica- 

 tion of this theory is about as follows : 

 Test for ^^ individual is about to undergo treatment 



Opsonic for infection by a certain germ. His blood is 



tested for its opsonic index, which indicates 

 whether or not his vital resisting powers are 

 above or below normal. If below normal he 

 is given a hypodermic injection of a specially 

 prepared culture of the germ which caused his 

 disease — ^the micro-organisms having previ- 

 ously been rendered harmless by heat. As a 

 result the opsonic power is at first diminished, 

 but this is invariably followed by a positive 

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