24 COLLECTED STUDIES L\ IMMUNITY. 



which fits to a group in a ferment-like body of normal serum, namely, 

 the complement (addiment). By virtue of these two haptophore 

 groups, the immune body functionates as a coupler or interbody. 

 carrying the action of the complement over onto the red blood-cells, 



In order to facilitate expression, that combining group of the pro- 

 toplasmic molecule to which the introduced group is anchored will here- 

 after be termed receptor. The side-chain, for example, which com- 

 bines with the tetanus toxin in the organism is such a receptor. The 

 tetanus antitoxin itself is nothing but the surplus of receptors thrust 

 off into the blood. Similarly, that complex which later functionates 

 as immune body is a receptor before being thrust off. 



In the further course of these investigations it has been found 

 that the function to produce peculiar antibodies analogous to immune 

 bodies is not confined to bacteria and erythrocytes. Cells of the 

 most varied kind, provided they are absorbed, excite the production 

 of immune bodies, in conformity with the requirements of the side- 

 chain theory. Landsteiner, Metchnikoff, and Moxter succeeded 

 in producing an immune serum against spermatozoa; von Dungern, 

 a specific serum w r hich acted on ciliated epithelium; and Mecthni- 

 koff, an immune serum against leucocytes and kidney epithelium. 

 Here also in the cases examined for this purpose (v. Dungern, Moxter) 

 it could be shown that the specific active substances are of complex 

 nature, consisting of an immune body and a corresponding comple- 

 ment, and that the immune body possesses a specific affinity for the 

 corresponding cells. 



The great theoretical significance of these investigations which 

 open up a new field to the study of immunity is clearly apparent, 

 but whether in the near future they will have any practical results 

 remains to be seen. 



In the pursuit of these studies, we were led to extend our researches 

 into another direction which seemed to us of special importance 

 in the understanding of pathological processes. 



The experimental investigations thus far made have dealt exclu- 

 sively with the changes in the serum which occur when an animal 

 is made to absorb foreign cell material. This mode of experiment, 

 however, is not limited in any way by the nature of the subject, but 

 is dependent entirely on the will of the experimenter, and it there- 

 fore lacks all physiological analogy. 



In pathology, the changes foremost to be considered are those 

 resulting from the absorption, by an organism, of its own cell mate- 



