DISSOCIATION OF IMMUNE-BODY 13 



to fresh corpuscles after contact for an hour at 37 C. ; that 

 is, two cubic centimetres of fresh corpuscles added as in the 

 above experiment will undergo complete haemolysis on the 

 addition of sufficient complement. Usually one dose of 

 immune-body can be obtained from red corpuscles con- 

 taining six haemolytic doses. Dissociation takes place also 

 at the temperature of the room, although much more 

 slowly ; while at C. it is practically nil. The separation of 

 immune-body can also be demonstrated without the actual 

 presence of fresh corpuscles. Three tubes are taken, each 

 containing 1 c.c. of suspension of red corpuscles treated with 

 excess, say twelve doses, of immune-body ; after an hour at 

 the room temperature the fluid is pipetted off and the cor- 

 puscles are repeatedly washed as before ; to each tube is added 

 1 c.c. of -8 per cent, sodium chloride solution. One tube is 

 placed in an incubator at 37 C. ; one is kept at the room 

 temperature ; and another is kept at C. At the end of an 

 hour the tubes are centrifugalized and the fluid from each is 

 added to 1 c.c. of untreated corpuscles ; sufficient comple- 

 ment is then added to produce lysis. It is found that in the 

 first tube a considerable amount of lysis results ; in the 

 secpnd a mere trace ; whereas in the third, there is no appre- 

 ciable lysis. This shows that at 37 C. corpuscles containing 

 multiple doses of immune-body give off a certain amount 

 to the surrounding fluid when this is free of immune-body. 

 In other words, there would appear to be in each case an 

 equilibrium between the combined and the free immune- 

 body which is reached after a certain time. This is one of 

 the most striking, and probably the most easily demon- 

 strable, examples of the dissociation of an anti-substance 

 from its antigen after combination. 



If in the experiment above, the sensitized corpuscles are 

 mixed with fresh corpuscles and then complement is added 

 at once, lysis takes place only in the sensitized corpuscles, 

 the others remaining almost unaffected. This is due to 



