PHENOMENA FOLLOWING IMMUNIZATION 81 



experiments of Nuttall as decisively contradicting the phagocytic 

 theory if the bactericidal action of the blood (for anthrax bacilli) 

 could be shown to be more potent in immune than in suscep- 

 tible animals." Metchnikoff l * himself, taking this point of view, 

 called attention to the fact that the blood serum of rabbits, animals 

 that are highly susceptible to anthrax, is more powerfully bactericidal 

 for these micro-organisms than is the blood of dogs or even that of 

 immunized calves, both of which are much more resistant than are 

 rabbits. Nuttall answered this by reporting that the blood of an- 

 thrax-immunized calves is actually more powerfully bactericidal than 

 is that of normal calves. Although this argument of Nuttall was 

 perfectly valid in principle, it exerted little influence on opinions 

 at this time because anthrax happens as a matter of fact to 

 belong to that group of infections in which bactericidal protection 

 is actually secondary to phagocytic, and Lubarsch could show that 

 the differences observed by Nuttall were often less than those 

 obtaining between specimens of blood taken from individual normal 

 rabbits. 



Lubarsch himself, then, in carefully planned experiments, 

 showed that rabbits and cats could be killed with quantities of anthrax 

 bacilli far less than the number which the extravascular blood of 

 these animals can destroy. He concluded that the resistance, in these 

 cases at least, is certainly not parallel with the bactericidal properties 

 of the blood, and suggested the possibility that the intravascular blood 

 does not possess bactericidal power to the same degree in which it is 

 possessed by the extravascular plasma or serum. This point, first 

 raised by Lubarsch namely, the possibility of a difference between 

 the intravascular blood and the extravascular blood serum or plasma 

 in bactericidal functions soon became one of the focal points of 

 the controversy, since Metchnikoff, admitting the bactericidal power 

 of the shed blood, assumed that this was purely the result of sub- 

 stances given off by the leukocytic cell-bodies after extravascular 

 injury. 



The Metchnikoff school defended its premise by the dual method 

 of attempting on the one hand to establish a parallelism between 

 phagocytic activity and natural resistance, and, on the other hand, 

 by showing that the cell-free blood serum of naturally resistant ani- 

 mals often furnished an excellent culture medium for the bacteria 

 in question. Thus Wagner showed that anthrax bacilli grow well 

 in the blood of fowls at 42 C., and Metchnikoff himself called at- 

 tention to the fact that pigeons' blood is an excellent medium for the 

 cultivation of the Pfeiffer bacillus, whereas the living pigeon is en- 

 tirely insusceptible to influenzal infection. Arguments based on 

 such observations, however, have lost much of their original weight, 

 for we have since then learned more about the delicate quantitative 

 11 Metchnikoff. Virch. Archiv, Vol. 97. 1884. 



