540 Chapter XVI 



In his last summary of the question, presented to the International 

 Congress of Medicine at Paris in 1900, Buchner^ maintains his theory 

 of leucocytic secretions. But he already takes one step more towards 

 the theory of phagocytosis, at least as regards natural immunity. 

 He consents to accept the fact " that phagocytic activity is in many 

 cases of decisive importance in overcoming the infective processes, 

 especially in those cases in which the secreted alexins were unable to 

 bring about more than a temporary attenuation of the vital functions 

 of the bacteria. Under these conditions the bacteria could only 

 be modified in so far as their chemical functions were transformed 

 into a latent state, from which they would be ready to regain their 

 full vital activity should it happen that the phagocytes were not 

 there to prevent them from doing so." In any case this view is 

 [564] widely removed from the old theory, according to which phagocytes 

 were regarded as capable of ingesting dead and inoffensive bacteria 

 only. 



A second adversary of the theory of phagocytosis, von Behring^, 

 gives a place to this theory not only in certain examples of natural 

 immunity but even in some cases of acquired immunity, e.g. in the 

 immunity of sheep vaccinated against anthrax, an example I have 

 already cited in Chapter viii (cf. supra, p. 242). 



It would take too long to describe the change of opinion on the 

 theories of immunity that has taken place during recent years. I will 

 content myself with citing certain examples which shall be taken from 

 the works of declared adversaries of the theory of phagocytosis. Thus, 

 Fliigge, who early declared against the cellular theory completely and 

 categorically and at the same time argued strongly in favour of the 

 humoral theory, has been gradually led to depart from his first position. 

 We may follow the steps of his conversion in the different editions 

 of his Outlines of Hygiene. In the first edition published in 1889 

 he expresses himself in the following manner ^ : ** Recent researches 

 indicate the probability, however, that the phagocytes in by far the 

 greater majority of cases seize the infective agents which, already 

 dead, are not in a condition suitable for the performance of a defensive 

 function. On the other hand, it is proved that the blood and blood 

 plasma of warm-blooded animals possess the property of destroying, 

 very quickly, enormous numbers of pathogenic bacteria," ... etc. In 



^ MUnchen. med. Wchnschr., 1900, S. 1193. 



2 Encyclop. JahrhUcher, Wien, 1900, Bd. ix, S. 203. 



3 "Grundriss der Hygiene," Leipzig, 1889, S. 487. 



