BACTERICIDAL ACTION OP NORMAL SERUM 209 



0-025 c.c. immune-body rabbit versus Staphylococcus aureus to which, 

 after two hours at 37 C., the test amount of red corpuscles + immune- 

 body was added, complete lysis resulted. 



It thus seems that while 0-01 c.c. of complement treated 

 with Staphylococcus aureus alone is sufficient to produce 

 complete lysis of the test corpuscles, 0-06 c.c. is required 

 when the complement has been treated with the Staphylococci 

 + immune-body. Although the serum leads to the taking 

 up of more complement, no bactericidal effect is brought 

 about ; in other words, even the increased amount of 

 complement brought into combination is not lethal to the 

 organisms. We tested the anti-staphylococcus serum in 

 varying amounts without any bactericidal action becoming 

 manifest. We may note that this serum when inactivated 

 was found to contain a large amount of specific opsonin 

 for the Staphylococcus aureus. 



In the case of the anti-typhoid serum a marked deviation 

 of haemolytic complement was also produced. For example, 

 in an experiment in every way similar to the above the 

 haemolytic dose of guinea-pig's serum treated with typhoid 

 bacilli alone was 0-0075 c.c., whilst the dose when the 

 serum was treated with typhoid bacilli + immune-body was 

 0-0*75 c.c., i.e. ten times as great. We failed, however, to 

 produce increased bactericidal action with this serum in- 

 activated at 55 C. in association either with guinea-pig's 

 or rabbit's normal serum. We found, however, a Neisser- 

 Wechsberg effect when a large amount of anti-serum (0- 1 c.c. ) 

 was used, this being sufficient to practically annul the 

 bactericidal effect of the normal serum. We also found, 

 as Buxton did, that the fresh typhoid serum had less bacteri- 

 cidal effect than fresh normal serum. 



In the case of the anti-F. Metchnikovi serum we found, 

 in addition to the presence of an immune-body as shown 

 by the absorption of complement, a marked bactericidal 

 action when reactivated. In testing, however, with varying 



arum P 



