8 COLLECTED STUDIES IN IMMUNITY. 



added to it, or it does so in only a very limited degree. When, how- 

 ever, new immune body is added, the blood-cells are completely dis- 

 solved. 



From these experiments we conclude that the sediment this time 

 contained both components, though not in equivalent proportion, 

 for there was an excess of immune body which became manifest 

 only on the addition of new addiment. Corresponding to this the 

 centrifuged fluid contained only faint traces of immune body and an 

 excess of addiment. 



The explanation of these phenomena presents no difficulties. It 

 must be assumed that under certain circumstances the immune body 

 and addiment enter into loose, readily dissociated chemical combi- 

 nation. This combination is hastened by heat and retarded by cold 

 in entire conformity to the views previously expressed by Ehrlich 

 (Werthbemessung des Diphtherie-heilserums, Jena, 1897). On the 

 other hand, the affinity existing between blood-cells and immune 

 body must be very strong, for these combine completely even in the 

 cold. We must therefore assume that the immune body possesses two 

 different haptophore groups, one with a strong affinity for the corre- 

 sponding haptophore group of the red blood-cell, and the other of feeble 

 chemical affinity, which is able to combine more or less completely with 

 the addiment present in the serum. At 30 C., therefore, the red blood- 

 cell attracts to itself not only the free molecules of immune body, 

 but also those which have already combined with the addiment in 

 the fluid. In the latter case the immune body represents in a measure 

 a link which ties addiment to the red blood-cells and subjects these 

 to the action of the addiment. In agreement with Pfeiffer, we regard 

 the phenomena appearing under the influence of the addiment as 

 analogous to digestion, and we shall probably not err if we regard the 

 addiment as having the character of a digestive ferment. Morgen- 

 roth, by the experiments in which by immunization he successfully 

 produced an antibody against rennin ferment, has made it very 

 probable that the ferments, like the toxins, possess two groups, 

 one a haptophore group and the other the actual carrier of the fer- 

 ment action. 



With this preliminary analysis all the various phenomena are 

 now readily explained. We assume that the immune body combines 

 with the small amount of digesting ferment normally present in 

 the blood, and then, by means of its other haptophore group, fitting, 

 for example, to red blood-cells or bacteria, carries this digestive 



