656 



COLLECTED STUDIES IN IMMUNITY. 



forty-five minutes at room temperature, the ox -blood suspension is added 

 and the mixtures kept for one hour at 37. After centrifuging, the sediments 

 are resuspended in physiological salt solution, and mixed with .0.075 cc. guinea- 

 pig serum. 



(B) Each tube contains 0.15 cc. antiserum, plus decreasing amounts of 

 inactive normal rabbit serum. After standing for forty-five minutes at room 

 temperature, the ox-blood suspension is added and the mixtures kept for one 

 hour at 37. After centrifuging, the sediments are mixed with 0.0015 cc. 

 rabbit amboceptor, kept at 37 for one hour, and again centrifuged. To these 

 sediments are then added 0.075 cc. guinea-pig serum. 



In this experiment each series again contains the some con- 

 stituents in like amounts, the main difference between them con- 

 sisting in the sequence in which the constituents are added. By 

 having varied this, we are enabled to exclude, in series B, the action 

 of the antiamboceptor. The result of the experiment is shown in 

 Table III. 



TABLE III. 



It will be seen that despite an increased amount of precipitable 

 substance, the precipitate exerts no binding action on complement. 

 In series A, on the other hand, the inhibiting action of the antiamboceptor 

 is again very marked. The experiment also shows that a relatively 

 slight excess of the normal rabbit serum paralyzes the antiamboceptor 

 action, a fact which finds a natural explanation in the interference 

 of the normal amboceptors. 



At first sight the results shown in series A seem somewhat similar 

 to those obtained in experiments made to determine the amount 

 of albuminous substance necessary to produce deflection of comple- 



