I Mechanism of immunity against micro-organisms 177 

 tural immunity against micro-organisms positive chemiotaxis is 

 cAhibited by the microphages more than by the macrophages. [187] 

 When we examine an inflammatory exudation and find a prepon- 

 derance of microphages we are satisfied that there has been an 

 intervention of micro-organisms. Even in the examples where it 

 is, at first, principally the macrophages which destroy the micro- 

 organisms (as in the case of the resistance of the animal organism 

 against the tubercle bacillus), there is also a great afflux of micro- 

 phages. The sensitiveness of the two chief categories of phagocytes 

 often exhibits a marked difference. We need merely recall to the reader 

 the example of the spirilla, ingested and destroyed exclusively by the 

 macrophages of the guinea-pig, which alone exhibit the necessary posi- 

 tive chemiotaxis. In many other examples of natural immunity the 

 part played by the macrophages is masked by that of the microphages. 



In natural immunity the motile phagocytes, having come up to the 

 invaders, perform a second physiological function ; they ingest the-~>; 

 micro-organisms. Sometimes the leucocytes devour at one swoop h 

 whole masses of these organisms, and carry out their work in a very / 

 short time. In other cases, especially when actively motile micro- 

 organisms, such as the spirilla of Obermeyer or of Sacharoff", haveQ 

 to be dealt with, the ingestion takes place with more difficulty and ( 

 requires special conditions. Thus, in order to ingest a spirillum, j 

 the macrophages of the guinea-pig throw out long conical processes. ] 

 Never in the ingestion of micro-organisms have I observed methods : 

 comparable to that by which the macrophages seize upon the red 

 corpuscles of birds or upon other animal cells. 



Some observers have expressed the opinion that micro-organisms 

 make their way into the cells spontaneously and do not need to be 

 drawn in by means of protoplasmic processes thrown out by the 

 phagocytes. It is of course indisputable that certain micro-organisms 

 may pass into the interior of the cell independently of any act of 

 phagocytosis. Such is the case with the malaria parasite and allied 

 species which make their way into the red blood corpuscles. But 

 here we are dealing with amoeboid organisms, quite capable of 

 perforating the wall of the red blood corpuscle by means of their 

 own pseudopodia. Bacteria, which do not possess amoeboid move- 

 ments, are deprived of this power of invasion. There are, however, 

 very rare cases in which such penetration does take place. For[i88] 

 example, Bizzozero^ has described spirilla in the stomach of the 

 1 Arch./, mikr. Anat., Bonn, 1893, Bd. xlii, S. 146. 

 B. 12 



