64 PROPERTIES OF KLEMOLYTIC SERA 



we cannot offer in every case an explanation ; no doubt 

 factors of different kinds are concerned. We will confine 

 our attention to the case of haemolysis of the ox's corpuscles 

 suspended in the heated serum of the guinea-pig. It will 

 be seen that the dose of complement is in this case about 

 three times the dose when the corpuscles of the ox are sus- 

 pended in their own serum. In other words, the guinea- 

 pig's serum would seem to protect the ox's corpuscles 

 against the toxic action (complement) better than the 

 ox's serum, or to be a more suitable medium in Bordet's 

 sense. On theoretical grounds it appears that some other 

 explanation must be looked for. It will also be seen that 

 the dose of complement necessary even when the corpuscles 

 are suspended in a mixture of equal parts of salt solution 

 and guinea-pig's serum 55 is greater than when the cor- 

 puscles are in their natural medium. 



We have inquired into the method by which the guinea- 

 pig's serum 55 retards lysis, that is, demands a higher dose 

 of complement. Theoretically there are at least two 

 possibilities, the one being that the heated serum in question 

 interferes with the combination of complement, the other that 

 it in some way retards the diffusion of haemoglobin. We 

 have found that the former is the chief factor in bringing 

 about the result. If the corpuscles be suspended in heated 

 serum of the guinea-pig and 3 M.H.D. of complement be 

 added (M.H.D. being the minimum dose in salt solution) 

 only slight lysis occurs in the course of two hours at 37 C. 

 Now if at the end of this time the surviving corpuscles be 

 removed from the serum, then washed and suspended in 

 salt solution and placed in the incubator for another period, 

 the corpuscles do not undergo lysis. Consequently active 

 complement has not entered into combination with them. 

 (It is to be noted that of course multiple doses of immune- 

 body were present to begin with.) 



We have also shown that in such a case as that men- 



