Syphilis 97 



Result. — No haemolysis. The corpuscles settle, leaving the 

 supernatant fluid clear and colourless. 



Explanation. — The normal human serum contains no ambo- 

 ceptor. It contains complement, as we shall show subsequently. 



Experiment 2. — This is the same as before, except that fresh 

 normal rabbit serum is substituted for human. The result and 

 the explanation thereof are the same as before. 



Experiment 3. — Take i volume of fresh serum from an 

 immunized rabbit, i volume of normal saline solution, and 

 I volume of emulsion of corpuscles. 



Result. — The corpuscles will be dissolved, the fluid being 

 coloured red from the liberated haemoglobin, and there will be 

 practically no deposit. 



Explanation. — The serum contains complement and amboceptor, 

 the latter being the result of the injections, the former a constituent 

 of all fresh sera. 



Experiment 4. — Take i volume of heated serum from an 

 immunized rabbit, i volume of normal saline, and i volume of 

 corpuscles, and incubate as before. 



Result. — No haemolysis. The corpuscles will probably be 

 clumped, owing to the injection having caused the production 

 of an agglutinin, similar to that which causes the Widal's reaction 

 in typhoid fever, but they will not be dissolved. 



Explanation. — The complement has been destroyed by heat, and 

 the serum contains amboceptor only. 



Experiment 5. — -Take i volume of fresh human serum, 

 I volume of heated immune serum, and again i volume of 

 corpuscles. 



Result. — Haemolysis. 



Explanation. — The fresh human serum, insufficient in itself to 

 cause haemolysis (see Experiment i), supplies the complement, 

 whereas the heated immune serum, also insufficient in itself to 

 cause haemolysis (see Experiment 4), supplies amboceptor, 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. 



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