148 HAEMOLYSIS EHRLICH'S RESEARCHES 



excess, and they break loose, they retain both their haptophore 

 groups and constitute amboceptor. The stimulation and over- 

 production is, of course, produced by the molecules of the substance 

 injected (the specific antigens), be they red blood-corpuscles, 

 bacteria, or, as we shall see, a whole host of other cells. 



As a rough illustration of the nature of these seizing arms 

 Ehrlich compares them with the tentacles of Drosera, which 

 seize the nutrient material and then secrete a digestive fluid. 

 The analogy is not exact, since the receptors do not form the 

 digestive enzyme, but simply select it from without. 



Ehrlich compares the action of the haemolysins with that of 

 the toxins, and points out that in each case there is a haptophore 

 group adapted to seize on the red corpuscle to be dissolved or the 

 cell to be poisoned, and an actively functional group with functions 

 resembling those of an enzyme. He says that the haemolysins 

 are practically toxins in two parts, and that a combination of these 

 parts is necessary before any action can be effected. 



These discoveries and theories of Ehrlich led to a series of 

 further researches, all of which were directly suggested by them, 

 and the results of which appear to corroborate them to the full. 

 Whatever the ultimate fate of the side-chain theory, there can be 

 no doubt that it has lead to an enormous increase of our knowledge 

 on a most intricate subject. These researches have in many 

 cases but little direct bearing at present on the subject of 

 immunity, but they are far too important to be passed over 

 without mention. We shall, therefore, summarize them as briefly 

 as is possible when dealing with so complicated a subject. We 

 will deal first with the explanation of the haemolytic action which 

 the serum of some normal animals has on the corpuscles of other 

 species ; for instance, normal goat serum will dissolve the red 

 corpuscles of the guinea-pig. This was shown conclusively to 

 depend upon the same mechanism of amboceptor and complement 

 as in the artificial immune sera. The proof was as follows : 

 Goat serum was mixed with guinea-pig's corpuscles, and the 

 mixture kept at o C., and then centrifugal ized. The theory would 

 lead us to believe that the amboceptor had combined with the 

 corpuscles, but that the complement had remained free. If this 

 were so, the supernatant fluid would be found to have lost 

 amboceptor. To test this a further addition of corpuscles was 

 made, and the solvent power of the serum for these was found 

 to be lowered. Evidently, then, sera which are naturally haemo- 



