THE COMPOUND H^EMOLYSINS 259 



and are now more of a formal than of a real character. 

 Evidently, if an animal reacts to injection of a foreign fluid 

 substance, the simplest way to explain this is to assume 

 that the injected fluid attacks some cell of the animal 

 chemically. In common language, we say that some sub- 

 stance in the fluid has been bound by the cells. The ani- 

 mal retaliates with the production of some substance, the 

 so-called antibody, which, as we have seen, partially binds 

 the reacting substance in the fluid ; if the reacting substance 

 be a cell, the antibody enters into similar cells, and in many 

 cases causes chemical alterations in the contents. As now 

 the reacting substance is bound chemically by the cells of 

 the inoculated animal, as well as by the antibody produced 

 by it, we may, with Ehrlich, for the sake of simplicity, sup- 

 pose that the antibody consists of just that part of the cells 

 which are attacked by the foreign fluid. But it is not 

 necessary to make this supposition. On a closer inspec- 

 tion, the side-chain theory seems to be little more than 

 a circumscription of the definition of the conception " anti- 

 body," under the further supposition that we are dealing 

 with chemical processes. If, as for the immune-bodies, 

 no proof has been given of their chemical action, the side- 

 chain theory finds, in its present state, no application. 



Bordet also makes an attack upon Morgenroth's l proof 

 that immune-body and alexin bind each other in solutions 

 containing both. As Morgenroth, 2 and likewise Ehrlich 

 and Sachs, 3 have later on conceded that the criticism of 

 Bordet is well founded, we will not here enter upon this 



1 Morgenroth: Centralbl.f. Baktcriologie, 35. 501 (1904). 



2 Morgenroth : Arbeiten aus dem pathologischen Institut zu Berlin, p. 6 

 (1906). 



8 Ehrlich and Sachs : /.<:., p. 1 6. 



