xxi] PATHOGENIC ORGANISMS 559 



of tissues or the animal the leucocytes present do contain 

 in their interior the bacteria, some more, some less degener- 

 ated. The first and tliird points may be taken to represent 

 phagocytosis in a mechanical sense, the second point may be 

 considered as leucocytosis owing to positive chemiotaxis. 



Now, while this represents the positive side of immunity, 

 the reverse, viz., the greater or lesser inability of the leuco- 

 cytes to rush to the bacteria, the greater or lesser inability 

 to take them up, and the greater or lesser inability to destroy 

 them, represent the negative side of complete or imperfect 

 immunity; that is to say: if the leucocytes are of this nature, 

 no immunity is present, the introduced microbes are not 

 interfered with, they live, thrive, and multiply and cause 

 infection and the disease. This is in essence the sum total 

 of the views and observations that Metchnikoff and his 

 school have put forward as sufficient to explain immunity 

 complete and incomplete. For a fairly complete literature 

 and history of this view see Lubarsch, Centralbl. f. Bakt. 

 utid Parasit., vol. vi.. No. 20. 



First as to the phenomenon of leucocytosis : it is notorious 

 that in many instances when microbes are injected into the 

 subcutaneous tissue of an insusceptible animal, or are intro- 

 duced in an attenuated form or in too small a number to 

 maintain themselves in the struggle for existence against the 

 living tissue, such leucocytosis does take place ; this is the 

 case when, for instance, a dose of anthrax bacilli is injected 

 subcutaneously into a normal adult rat, or a dog, or into 

 the lymph sac of a normal frog, or if a small dose of bacillus 

 of symptomatic charbon is injected into the subcutaneous 

 tissue of the little susceptible rabbit, or if a fair dose of 

 moderately virulent bacillus typhosus or of vibrio cholerse is 

 injected subcutaneously into the guinea-pig. But this is by 

 no means universally the case. Take, for instance, the case 



