IMMUNITY. 391 



leucocytes, together with reduction of the alka- 

 linity of the tissue fluid, goes on in the body 

 itself, basic bodies accumulate and act as auto- 

 toxins, and the leucocytosis becomes of an in- 

 jurious character, e. g. post-hsemorrhagic, ca- 

 chectic or ante-mortem. Hildebrandt rendered 

 rabbits immune against the ferment emulsin, 

 and these animals then showed immunity like- 

 wise against the bacteria of rabbit-septicaemia. 

 A sort of natural immunity existed normally 

 and this was heightened by a special impulse 

 which simulated a specific protective inocula- 

 tion. In all these cases other " active " proteid 

 bodies acted as a stimulus upon the body cells 

 in just the way that " active " bacterial proto- 

 plasm is supposed to do. Natural immunity 

 is thus united by a series of intermediate links 

 with acquired and specific immunity. The 

 common feature lies in the stimulation of the 

 particular cell territories and wandering cells 

 which are necessary for defence. 



Not even bodies of the kind under consider- 

 ation, however, are essential. Ordinary chem- 

 ical substances, if they are able to interfere in 

 the continuity of energy, act in a similar way. 

 This is indubitably true of those cases in which 

 the cure depends upon the excitation of inflam- 

 mation, and Liebreich has done us the great 

 service of showing that in tuberculosis the 



