96 PATHOGENIC BACTERIA. 



in the older areas the streptococci are nearly all free." 

 Is it possible that the extent of the disease is being con- 

 tested by leukocytes waging an active warfare against 

 the cocci, and that their success results in the demar- 

 cation of the disease? 



As there is abundant evidence on all sides to show that 

 the leukocytes do take up bacteria, the solution of the 

 question of the relationship of the phenomenon to im- 

 munity must depend upon the demonstration of certain 

 involved questions. 



i. Do the leukocytes take up living bacteria? There 

 are many reasons for thinking that in the illustrations 

 cited, the bacteria may have been already dead when 

 taken up by the leukocytes, having met their fate from 

 other causes and become transformed into inert parti- 

 cles upon which the leukocytes react as upon molecular 

 substances in general. MetschnikofF, 1 however, is pre- 

 pared to demonstrate that the bacteria which tjie leuko- 

 cytes attack are alive, for he successfully isolated leuko- 

 cytes containing spores of anthrax, and upon transferring 

 them to culture-media in which they died, observed the 

 germination of the contained spores into bacilli. It must 

 be remembered, however, that the resistance of the spore 

 to deleterious influences is very great, so that it might be 

 able to survive where adult bacilli would succumb. Also, 

 that the spore, which as such is probably devoid of poi- 

 sonous or irritative properties, might be seized upon when 

 the adult bacillus would be carefully avoided by the leu- 

 kocyte. However, whether in this case we are willing to 

 accept the evidence as conclusive or not, there are abun- 

 dant confirmations of the fact that the cells do take up 

 living bacteria, for in various infectious diseases we find 

 it not uncommon for the cells themselves to fall victims 

 to the bacteria they have taken up. This is seen in such 

 diseases as mouse septicemia, gonorrhea, tuberculosis. 



It is interesting to find that the phagocytes evince an 



1 Vircko-u? s Archives, xcvi., p. 177 ; xcvii., p. 502. Annates de P Inst. Pas- 

 teur, 1887, i., p. 321. See also Etudes sur r Inflammation, Paris, 1892. 



