1905.] 



On Spontaneous and other Phagocytosis. 



219 



•VOr 



Duration of Che heating. 

 5' to' 13' 20' zj' 30' 



30- 



v<*3< 



01 1 1 1 1 1 



Curve 4. 



Investigation of the Question as to whether tlie Incitor Substance which is found 

 in the Heated Serum of Persons who have responded to Tubercular 

 Infection, or as the Case may be to an Inoculation of Tubercle Vaccine, is 

 a Leueocytotropic Element — to which the Appellation " Stimulin " would 

 Apply — or Bacteriotropic Element, to which the Term " Opsonin " would 

 Apply. 



The absorption method of Ehrlich, which has already been employed by 

 Neufeld and Eimpan in connection with the investigation of the nature of 

 the incitor element contained in the serum of animals immunised against 

 streptococcus and pneumococcus, was obviously the method indicated for 

 employment in connection with the problem here before us. It was also 

 manifest, in view of the facts detailed in the previous section, that the 

 comparative experiments instituted with heated immune serum before, and 

 after digestion with tubercle bacilli and subsequent centrifugalisation, would 

 yield unfallacious results only on adhering rigidly to the same conditions in 

 the matter of the heating of the serum, and on arranging the experimental 

 conditions in such a manner as to achieve in the phagocytic mixtures 

 employed in each case a salt content of over 1 per cent. NaCl. 



A series of experiments conducted with these precautions showed in an 

 uniform manner that the incitor element can be completely extracted from 

 heated immune serum by digestion for half an hour at 37° C. with a sus- 

 pension of tubercle bacilli.* 



It is thus clear that the incitor element which is found in heated serum of 



* This result is in conformity with the results obtained by Neufeld and Eimpau in 

 connection with streptococcal and pneumococcal immune serum, and by Dean in connec- 

 tion with staphylococcal immune serum. 



