24 STUDIES IN IMMUNITY. 



A control guinea-pig "B," weighing 400 grams, had been vacci- 

 nated in the same manner as "A." One-sixth of a culture was 

 given this animal without chloroform. In 20 minutes the leucocyte 

 count had fallen from 9500 to 5000. At this time the blood was 

 sterile; liver, lung and spleen gave positive cultures. 



II. LEUCOCYTES AND THE BACTERICIDAL POWER OF SERUM. 



Phagocytosis is not of secondary importance in the mechanism 

 of cholera immunity. Leucocytes take up vibrios which soon show 

 alterations in form and reaction to dyes within the protoplasm, 

 which indicates that they have been affected by some harmful 

 substance. Is it not possible that the bactericidal substance in 

 serum comes from the leucocytes? Metchnikoff has already offered 

 the suggestion (1887) that the bactericidal substances of serum 

 might be of leucocytic origin. In 1899 he wrote:* "I might add 

 that those who have asserted that the action of serum against 

 bacteria is independent of leucocytes have not taken into considera- 

 tion those substances liberated in the serum as the result of the 

 destruction of leucocytes. It has been repeatedly noticed that 

 these cells when removed from their normal surroundings break 

 up and liberate their contents into the surrounding fluid." Hankinf 

 and an English experimenter, Kanthack, later attributed to 

 the eosinophiles the secretion of bactericidal substances. Accord- 

 ing to this conception these latter cells may be broken up in the 

 blood stream and so affect the micro-organisms that have entered 

 the body. Bacteria, killed or attenuated by contact with these 

 substances, might later on be taken up by phagocytes. According 

 to this conception also it is the phagocytes which form the bacteri- 

 cidal substances. The engulfing of bacteria by living cells instead 

 of being a phenomenon essential to the defense of the organism 

 would be rather an accessory phenomenon subsequent to the 

 destruction of the bacteria by bactericidal substances dissolved in 

 the plasma. 



* Annales de 1'Institut Pasteur, December, 1889. 



t Hankin, Ueber den Ursprung und Vorkommen von Alexinen im Organismus 

 (Centralblatt fur Bakteriologie, 12, Nos. 22 et 23, December, 1892); Ueber die 

 Theorie der Alexocyten (Centralblatt fur Bakteriologie, 14, No. 25, December, 

 1893). 



