ILEMOLYSINS AND ALLIED BODIES 445 



alexin, the latter is called by Ehrlich a complement (F in diagram), 

 and the haptophoric group of the amboceptors, on to which it fits, 

 is called the complemento-philic group (Com. in (4) of Fig. 22), 

 the opposite haptophoric group being called cytophilic (Cyt. in (4) 

 of Fig. 22), because it fits the receptors of the invading cell. It 

 is, according to this theory, the amboceptors which are produced 

 by injection, the complements being present in normal blood. The 

 complements act on the erythrocyte, when suitable amboceptors 

 are present to chain them together. 



We must now discuss the experiments on which Ehrlich and 

 Morgenroth base this theory. They had already learned, from 

 Bordet's observations, that two substances were concerned in 

 haemolysis ; the one of these called an alexin being a normal 

 constituent of the tissue fluids, easily destroyed by heat, and 

 possessed of digesting properties ; the other called substance 

 sensibilatricc being produced by inoculation, endowed with much 

 greater stability than the alexin, and which acted by sensitising 

 certain cells towards the alexin. In order to explain haemolysis 

 by the side-chain theory, Ehrlich and Morgenroth had first of all 

 to show that the substance sensibilatrice of Bordet actually com- 

 bined in definite chemical union with the cell, and that the 

 so-called alexin then attached itself to the resulting compound, 

 this being the only possible way by which alexin and cell could 

 unite so as to permit the digesting or lysogenic power of the alexin 

 to assert itself. 1 



For their experiments, Ehrlich and Morgenroth injected 

 sheep's blood into a goat, the goat's serum being thereby ren- 

 dered haemolytic towards sheep's erythrocytes. The experiments 

 concerned themselves with the following questions : 



I. Does the amboceptor become combined with the erythrocyte? 



Hsemolytic goat's serum was inactivated by heating it to 

 55 C. After cooling, it was mixed with thoroughly washed 

 sheep's erythrocytes. This mixture after standing some time 

 was centrifugalised, and the sediment and supernatant fluid sepa- 

 rately tested for the presence of amboceptors. The supernatant 

 fluid was, for this purpose, mixed with sheep's erythrocytes and 



1 To prevent confusion of terms we will, from this stage on, adopt Ehrlich 

 and Morgenroth's nomenclature, calling Bordet's alexin the complement and the 

 substance sensibilatrice the amboceptor. 



