140 MICROBES AND TOXINS 



phosphate of lime and may be dissolved by an acid. Obser- 

 vation of these tubercles at different stages shows that the 

 concentric layers correspond to secretions of the bacillus which 

 has been defending itself against the phagocytes. Analogous 

 formations are known in actinomycosis (the club-forms of 

 the granules). There is no essential difference between the 

 struggle of the tubercle bacillus against the giant cell and the 



Tubercle 

 bacillus 



FIG. 54. Giant cell enclos- 

 p IG . 53. Giant cell from the ing the final stage of a 



spleen of the jerboa : it con- calcareous particle, 



tains a tubercle bacillus sur- 

 rounded by concentric layers. 

 (Metchnikoff.) 



struggle of the gregarines and the nematodes (larvse of Gordius 

 or Rhabditis) against the phagocytes of the worm. 



Inflammation is thus defined by phagocytosis : the vessels 

 and nerves have their importance, but are merely accessory. 

 Infection, inflammation, and immunity can all be seen in 

 miniature in the examples of the Bipinnaria with its splinter 

 surrounded by motile cells, and of the Daphnia with its 

 globules in the act of devouring the spores of Monospora. 



