PHAGOCYTOSIS 41 



stimulus is given to its already sensitised cells to 

 produce a further supply of immune bodies; these, 

 being much in excess of the normal physiological 

 requirements, may become quickly resorbed, thereby 

 giving rise to a further production of anti-anti- 

 bodies. Now, if the anti-antibodies be in excess, 

 their primary action is to alter the phagocytic 

 powers of the leucocytes, by weakening or destroying 

 their neutralising property, and by so doing enabling 

 the engulfed vibrios to destroy the leucocyte, with 

 its consequent disintegration and liberation of the 

 contained toxin. Accordingly, as the amount of 

 anti-antibodies increases, the bacteriolytic or bacteri- 

 cidal action of the serum decreases, the result being 

 an enormous increase in the virulent living organisms 

 within the animal body, which by this time has 

 probably succumbed to the overwhelming amount of 

 toxin liberated. We thus find that a guinea-pig 

 which receives the minimum lethal dose of cholera 

 vibrios dies with all the symptoms of cholera poison- 

 ing, death being caused by the endotoxins liberated 

 from the vibrios, which have been engulfed by the 

 leucocytes; for, on autopsy of the guinea-pig, there 

 are no vibrios to be found. We therefore see that, 

 although phagocytosis w^as sufficiently active to 

 remove all the micro-organisms, yet the leucocytes 

 had lost their power to neutralise the endotoxins of 

 the bacteria they had engulfed. Again, if the amount 

 of virulent organisms injected be increased above the 

 minimal lethal dose, the animal dies with the same 



