SYPHILIS 121 



ment, whereas the heated immune serum, also insufficient in 

 itself to cause haemolysis (see Experiment 4), supplies ambo- 

 ceptor, and the ingredients of the mixture are the same as in 

 Experiment 3. 



EXPERIMENT 6. Repeat this, except that in place of the fresh 

 human serum use heated human serum, the other ingredients 

 being as before. 



Result. No haemolysis. 



Explanation. The complement has been destroyed by the 

 heating, and the constituents of the mixture are the same as 

 in Experiment 4. 



EXPERIMENTS 7 AND 8. These are the same as Experiments 

 5 and 6, except that rabbit serum is used in place of human 

 serum. The results and explanations are the same, and show 

 that fresh rabbit serum contains complement, which is 

 destroyed by heat. 



Two further experiments show that amboceptor can attach 

 itself to corpuscles, whereas complement cannot do so. 



EXPERIMENT 9. Take the deposit from the tube in Experi- 

 ment i or 2, and add to it i unit of heated immune rabbit 

 serum, and incubate again. 



Result. No haemolysis. 



Explanation. The corpuscles have been exposed to the 

 action of complement in the first part of the experiment, but 

 have not absorbed it, or they would become dissolved when 

 the heated immune serum (amboceptor) is added. 



EXPERIMENT 10. Take the deposit from Experiment 4, and 

 add to it i unit of fresh normal human or rabbit serum. 



Result. Haemolysis. 



Explanation. In the first phase of the experiment the cor- 

 puscles had absorbed amboceptor or, as it is usually expressed, 

 had become sensitized. The second serum contained com- 

 plement, and the conditions of haemolysis were reproduced. 



Experiments such as these lead us to regard the process of 

 haemolysis somewhat as follows : The amboceptor first com- 

 bines with the corpuscles, sensitizing them. Comple- 

 ment now combines with the amboceptor, which acts as a 

 sort of link, combining the two substances together. The 

 whole compound of corpuscle amboceptor complement is 

 called a "haemolytic system," and undergoes solution at the 

 body temperature. It will be obvious that corpuscles which 



