512 Chapter XVI 



pathogenic micro-organisms. Thus, Chauveau^ was not long before 

 [535] he undertook experiments having for their object the determination 

 of the fate of anthrax bacilli when injected into the blood vessels of 

 Algerian sheep. He found that tliese organisms disappeared from 

 the blood at the end of a few hours, but they were then to be found 

 accumulated in the lung, spleen, and certain other viscera. In these 

 positions the bacilli become incapable of reproducing themselves and 

 in refractory individuals soon disappear, being opposed by the inhibi- 

 tory substances of the blood plasma. 



The two theories just sketched have this point in common, that 

 they both attribute the natural or acquired immunity to humoral 

 and purely passive properties. According to one theory it is the 

 impoverishment of the fluids of the animals which prevents the 

 development of the pathogenic organism, whilst according to the 

 other it is the presence of some bacterial poison which brings about 

 the same result. To give experimental support to his theory Pasteur 

 brought forward his attempts at sowing micro-organisms in culture 

 media exhausted by a previous develoi)ment of the same organism, 

 eliminating, so to sa;y, the active influence of the animal organism. 

 It is true that, in order to explain natural immunity, it was necessary 

 to ascribe a role to the "constitution'' and to the "vital resistance," 

 interpreting this, as Naegeli had already done, in the sense of a 

 competition for the oxygen and the nutritive substances between the 

 parasites and the cells of the body. 



Adopting this point of view, Hans Buchner^, a pupil of Naegeli, 

 attempted to gain a more precise idea of the conditions under which 

 acquired immunity against infective diseases is set up. He developed 

 his theory in various publications ; this theory consists, briefly, in the 

 property of the animal organism to reinforce the local resistance of the 

 organs by means of an inflammatory reaction. The starting-point of 

 this local theory is the thesis that each pathogenic micro-organism 

 can only manifest its pathogenic action when it enters the particular 

 organ in which it is capable of living and maintaining itself. Thus, 

 the pneumonococcus can live in the lungs only, the cholera vibrio in 

 the intestines only, and so on. Every time that a pathogenic micro- 

 organism becomes localised in its special organ, an inflammatory 

 action is set up which results in the reinforcement of the living 



^ Compt rend. Acad. d. sc, Paris, 1880, t xci, p. 680. 



2 "Die Naegeli'sche Theorie d. Infectionskrankheiten," Leipzig, 1877; "Eiue neue 

 Theorie iiber Erziel v. Immunitat," Miinchen, 1883. 



