76 STUDIES IN IMMUNITY. 



important proofs of the accuracy of this conception and the facts 

 brought out in this article do not change our opinion. It has been 

 established that in vaccinated animals the phagocytes have their 

 protecting properties distinctly increased. Not only is the tactile 

 sensitivity of their phagocytes more perfect as Massart has shown,* 

 so that they can take up the struggle with their adversaries more 

 preparedly, but we believe that it may be granted that the bac- 

 tericidal properties of their body fluids are increased. In certain 

 cases, as with the vibrios, the antiseptic property of leucocytes 

 is increased to such an extent that it is liberated in the surround- 

 ing fluid, either on removing the blood from the body or by some 

 harmful effect on the leucocytes. The substances diffused from 

 these leucocytes in the blood fluid may then bring about destruc- 

 tive changes in bacteria. When serum is endowed with bactericidal 

 properties it owes them to the leucocytes; the bactericidal power of 

 serum is only a reflection of the power within leucocytes, and is 

 present only in a relatively feeble degree. 



A bactericidal property is not always present in the serum of 

 immunized animals. The sera from animals vaccinated against 

 tetanus, diphtheria, hog-cholera, etc., do not destroy their respective 

 organisms. May we conclude in these instances that the bacterici- 

 dal substance is lacking in the serum? Must we make a distinction 

 between those instances in which the serum of immunized animals 

 is bactericidal and those in which it is not? Since the bactericidal 

 power of serum indicates the destructive power of phagocytes, are 

 we authorized in these instances of diphtheria or hog-cholera in 

 considering the absence of bactericidal properties in serum as indic- 

 ative of little bactericidal activity in the phagocytes? 



Such a conclusion would not be legitimate. It would seem rather 

 that there is a regular increase of bactericidal property in phagocytes 

 in immunity and that we know now only of certain general examples 

 of this fact. And if the increase of this property is not evident in 

 certain cases by a notable increase in the bactericidal property of 

 the serum, it is apparently due to the fact that certain micro- 

 organisms possess a relatively higher resistance to such properties. 

 Not all bacteria are equally easily destroyed by those diluted bac- 



* J. Massart, Le chemiotaxisme des leucocytes et I'lmmunite*. Annales de 

 1'Institut Pasteur, May, 1892. 



