The " Lateral-chain Theory" of Immunity 117 



by centrifugalization, we investigated whether these substances had been taken 

 up by the red corpuscles or remained behind in the fluid. The proof of its loca- 

 tion in the one position or in the other was readily forthcoming, since to restore 

 the hemolysin to its former activity, it was only necessary to add to the ' immune 

 body' a fresh supply of 'complement,' or to the 'complement' a fresh supply of 

 'immune body' in order that the presence of the hemolysin in its integrity 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 oC. 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 oC., it was found after centrifugalizing 

 that, under these circumstances also the 'immune body' had united with the 

 red blood-corpuscles, but that the 'complement' remained in the serum. This 

 experiment showed that both components must, at a tem- 

 perature of oC., 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 compo- 

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

 In the first place, two haptophore groups must be as- 

 cribed to the * immune body,' one having affinity for a 

 corresponding haptophore group of the red blood-corpuscles 

 and with which at a lower temperature it quickly unites, Fig. 25. Com- 

 and another haptophore group of a lesser chemical affinity, bination of cell (a), 

 which at a higher temperature becomes united with the amboceptor (6), and 

 'complement' present in the serum. Therefore at the complement (c). 

 higher temperature the red blood-corpuscles will draw to The amboceptor 

 themselves those molecules of the 'immune body' which in may unite with the 

 the fluid have previously become united to the 'comple- cell, but cannot af- 

 ment.' In this case the 'immune body' represents in a feet it alone. The 

 measure the connecting chain which binds the comple- complement cannot 

 ment to the red blood-corpuscles and so brings them unite with the cell 

 under its deleterious influence. Since under the influence except through the 

 of the 'complement' at least, in the case of the bacteria amboceptor, having 

 appearances are to be observed (for example, in the no adaptation to the 

 Pf eiffer phenomenon) which must be regarded as analogous cell directly, 

 to digestion, we shall not seriously err if we ascribe to 



this 'complement' a ferment-like character." .... "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 becomes possible for us to 

 attempt to solve the mystery of the origin of these bodies. I have in the begin- 

 ning of this lecture fully developed the 'side-chain theory,' according to which 

 the antitoxins are merely certain of the protoplasm 'side-chain' which have 

 been produced in excess and pushed off into the blood. 



"The toxins as secretion products of the cells are in all likelihood still relatively 

 uncomplicated bodies; at least by comparison with the primary and complex 

 albumins of which the living cell is composed. 



"If we now recognize that the different lysins arise only through absorption 

 of highly complex cell material such as red blood-corpuscles or bacteria then 

 the explanation, in accordance with what I have said, is that there are present 

 in the organism 'side-chains' of a special nature, so constituted that they are 

 endowed not only with an atomic group by virtue of the affinities of which they 

 are enabled to pick up material, but also with a second atomic group, which, being 

 ferment-loving in its nature, brings about the digestion of the material taken up. 

 Should the pushing off of these 'side-chains' be forced, as it were, by immuni- 

 zation, then the 'side-chains' thus set free must possess both groups, and will, 

 therefore, in their characteristics entirely correspond with what we have placed 

 beyond doubt as regards the 'immune body' of the hemolysin." 



