194 INFECTION AND RESISTANCE 



gether in concentrations which lie within definite zones of relative 

 proportions. The visible precipitation would seem, therefore, to be 

 merely a secondary phenomenon, the essential one being the union of 

 an antigen with a sensitizer by which it is rendered amenable to the 

 action of the alexin. This would enable us to comprehend also the 

 experiments of Friedberger, discussed in the section on anaphylaxis, 

 in which it was shown that the action of alexin upon precipitates 

 gives rise to the formation of toxic bodies just as this occurs when 

 alexin acts upon sensitized cells. It leads, moreover, to a compre- 

 hension of the processes of the digestion of intravascularly intro- 

 duced foreign proteins, which are rendered amenable to the digestive 

 action of the alexin by the antibodies spoken of as precipitins, which 

 functionally and in structure are conceived as identical with other 

 sensitizers. 



Dean, 95 who has lately analyzed the relation between precipita- 

 tion and alexin fixation on the basis of extensive experimentation, 

 comes to the conclusion that the proportions of antigen and antibody 

 which are favorable for rapid and complete precipitation do not 

 favor the most complete alexin fixation. He states that the two reac- 

 tions do not run a parallel course but believes that this does not mean 

 that they are necessarily distinct phenomena. He says : "They rep- 

 resent two phases of the same reaction ... a flocculent precipitate 

 represents the final stage of a change which can be recognized in its 

 earliest and incomplete stage by means of a complement fixation." 



Our view differs from this only in that we believe that the pre- 

 cipitation is merely a secondary, colloidal phenomenon, which may, 

 or may not, coincide with the phase of greatest alexin fixation, ac- 

 cording to other fortuitous conditions which may favor or retard 

 flocculation. Indeed, if our view be accepted, rapid compact pre- 

 cipitation may possibly be assumed to interfere with alexin fixation 

 in that it would inhibit perfect contact of the alexin with the antigen- 

 antibody complexes. 



Another view of the mechanism of alexin fixation is that which 

 has been advanced by Neufeld and Haendel. 96 These workers have 

 found that sensitized cholera spirilla will fix hemolytic complement 

 at C., whereas the same bacteria at 37 C. will fix both the hemo- 

 lytic and the bactericidal complement. They conclude from this that 

 the fixation at 37 C. was brought about by virtue of the bactericidal 

 amboceptor, whereas at C. fixation was brought about by an anti- 

 body which is distinct from amboceptor or sensitizer. They believe 

 from this and other observations, which we cannot consider in detail, 

 that alexin fixation may be brought about by a special fixing anti- 



95 Dean. Zeitschr. f. Imm., Vol. 13, 1912. 



96 Neufeld and Haendel. Arb. a. d. kais. Gcsund., Vol. 28, 1908. 



