The ''Lateral-Chain Theory" of Immunity 119 



might be shown by the occurrence of solution of the red 

 cells. The experiments proved that, after centrifugalizing, 

 the 'immune body' is quantitatively bound to the red blood- 

 corpuscles, and" that the 'complement/ on the contrary, 

 remains entirely behind in the fluid. The presence of the 

 two components in contact with blood-corpuscles only 

 occasions the solution of these at higher temperatures, and 

 not at o C. And an active hemolytic serum (with 'immune 

 body' and 'complement' both present) having been placed 

 in contact with red blood-corpuscles and maintained for a 

 while at o C., it was found after centrifugalizing that, under 

 these circumstances also the 'immune body' had united with 

 the red blood-corpuscles, but that the 'complement' re- 

 mained in the serum. This experiment showed that both 

 components must, at a temperature of o C., have existed 

 alongside of one another in a free condition." .... 



"But when analogous experiments were undertaken at a 

 higher temperature it was found that both components were 

 retained in the sediment. 



"These facts can only be explained by making certain 

 assumptions regarding the constitution of the two com- 

 ponents, i. e., of the 'immune body' and the 'complement.' 

 In the first place, two haptophore groups must be ascribed 

 to the 'immune body,' one having affinity for a correspond- 

 ing haptophore group of the red bleod-corpuscles and with 

 which at a lower temperature it quickly unites, and another 

 haptophore group of a lesser chemical affinity, which at a 

 higher temperature becomes united with the 'complement' 

 present in the serum. Therefore at the higher temperature 

 the red blood-corpuscles will draw to themselves those 

 molecules of the 'immune body' which in the fluid have 

 previously become united to the 'complement.' In this 

 case the 'immune body' represents in a measure the connect- 

 ing chain which binds the complement to the red blood- 

 corpuscles and so brings them under its deleterious influence. 

 Since under the influence of the 'complement' at least, in 

 the case of the bacteria appearances are to be observed 

 (for example, in the Pfeiffer phenomenon) which must be 

 regarded as analogous to digestion, we shall not seriously 

 err if we ascribe to this 'complement' a ferment-like char- 

 acter." .... "Having obtained a precise conception 

 of the method of action of the lysins of the serum of the 

 hemolysins, and thereby also of the bacteriolysins it be- 



