40 VACCINE AND SERUM THERAPY 



cytes, therefore in the above experiment phagocytosis 

 must be sufficiently active to engulf the disintegrating 

 vibrios and at the same time neutralise their liberated 

 endotoxins to such an extent that they had no visible 

 reaction on the guinea-pig. The leucocytic activation 

 must be due to what Wright calls opsonins, but what 

 other authorities believe to be nothing more than the 

 bacteriolytic or bactericidal amboceptors contained in 

 the immune serum. 



We next come to the latter part of the phenomenon 

 occurring in the above experiment. On the guinea- 

 pig recovering from the first injection of immune 

 serum and ordinarily fatal dose of cholera vibrios, if 

 it be given, say, five times the original dose of 

 vibrios, not even ten thousand times the amount of 

 the previous dose of immune serum will protect it. 

 W^hat is the explanation of this ? Personally, I think 

 it is the following : During the reaction between the 

 tissue fluids, the immune serum, and injected vibrios, 

 within the body of the guinea-pig, caused by the first 

 injection of immune serum and virulent vibrios, there 

 was an active production of immune bodies in the 

 guinea-pig's serum. If these bodies were produced 

 in excess, they were liable to become resorbed, 

 thereby giving rise to anti-antibodies ; therefore, on 

 the animal recovering from the effects of the first 

 injection of immune human serum plus an ordinarily 

 fatal dose of vibrios, its serum contained free anti- 

 bodies and anti- antibodies. When the guinea-pig 

 receives the second, but larger, dose of vibrios, a new 



