FURTHER DEVELOPMENT OF KNOWLEDGE 191 



or guinea pig corpuscles, it acquired the property of preventing the 

 hemolysis of these corpuscles if, later, it was brought together with 

 them in the presence of specific hemolysin and alexin. Gray now 

 showed hy experiment that Sachs' method was referable to insuffi- 

 cient washing of the corpuscles. When, in the first contact, the rab- 

 bit serum was exposed to the sheep corpuscles, a certain amount of 

 sheep serum adherent to the cells was carried over into the rabbit 

 serum. This sheep antigen later reacted with the antisheep pre- 

 cipitin present in the hemolytic immune serum and, in this way, 

 fixed alexin and prevented hemolysis. 



It seems that the analysis of Gay is correct, and that Sachs' 

 conclusion as well as thpse of Pfeiffer and Friedberger, by analogy, 

 cannot be taken as demonstrating the existence of specific anticom- 

 plements or anti-amboceptors. Gay has further offered the same 

 mechanism as an explanation of the Neisser-Wechsberg phenomenon, 

 which has been discussed in another place. 



To summarize, then, we have learned that there are a number of 

 varieties of specific alexin absorption or fixation processes, one that 

 is exerted by cells treated with specific sensitizer, be they blood or 

 bacterial, the other that which occurs when unformed protein is 

 brought into contact with its specific antiserum. The latter has been 

 correlated with the precipitin reaction, in that it has been found that, 

 whenever a specific precipitate is formed in such reactions, it is this 

 precipitate on which the fixation depends. On the other hand, it is 

 necessary to note that the formation of a precipitate is by no means 

 necessary for the fixation, for, as is well known, if a series of pre- 

 cipitin tubes are set up, in each successive one of which the amount 

 of antigen is diminished, a degree of dilution will soon be reached 

 at which no visible precipitate will occur, but which nevertheless 

 will show alexin fixation. The following is an illustration of such 

 an experiment: 



From such experiments it follows moreover that the fixation of 

 alexin, carefully titrated, is a more delicate method of determining 



