FURTHER DEVELOPMENT OF KNOWLEDGE 181 



fell out after dialysis of 24 hours or more, almost without exception, 

 retained moderate or slight hemolytic properties, which could not be 

 removed until the precipitate had been dissolved in salt solution and 

 reprecipitated with distilled water two or three times. This would 

 imply that a minute amount of the end-piece, carried down in pre- 

 cipitation, must suffice to activate the mid-piece and would seem 

 to point to the fact that in whole serum the two fractions are present 

 as a complex and not separately. This question has been much dis- 

 cussed and many facts have been brought out on both sides. Hecker 

 showed that the combination of mid-piece with the sensitized cells 

 can take place at a temperature of C., while that of end-piece 

 with the "persensitized" cells requires a considerably higher tem- 

 perature. The bearing this fact may have upon similar earlier ex- 

 periments of Ehrlich and Morgenroth upon the thermal conditions 

 governing the union of amboceptor and complement with antigen is 

 self-evident. In the present connection, however, the fact that the 

 two fractions may be separately absorbed out of the serum by sensi- 

 tized cells at C. would suggest the probability of their being sep- 

 arate in the whole blood. No crucial experiment has so far been 

 possible, and there is not enough evidence on either side as yet to 

 justify a definite opinion. However, the experiments of Michaelis 

 and Skwirsky and later ones of Skwirsky alone have much indi- 

 rect bearing on this question, though final interpretation is as yet 

 impossible. Michaelis and Skwirsky, 55 after determining that an 

 acid reaction inhibits the hemolysis of sensitized blood cells, found 

 that under such conditions "mid-piece" alone is bound, but that 

 "end-piece" or the albumin fraction is left unbound. They recom- 

 mend the use of strongly sensitized cells in an acid medium as a 

 method of obtaining free "end-piece" from serum. 



Skwirsky 56 subsequently found that during the ordinary Wasser- 

 mann reaction the complex of syphilitic serum and antigen binds 

 the mid-piece only. If the Wassermann reaction has been strongly 

 positive ; that is if there has been absolutely no hemolysis, and we 

 remove the supernatant fluid by centrifugation, active end-piece can 

 be demonstrated in it by the addition of persensitized cells. Bron- 

 fenbrenner and Noguchi have also studied this phenomenon, but do 

 not believe that Skwirsky's experiments prove that end-piece is free 

 in such "fixation" supernatant fluids. These supernatant fluids, ac- 

 cording to them, differ from all other "end-pieces" in that they are 

 active upon persensitized sheep corpuscles only, but not upon other 

 cells. An explanation for this is lacking. 



There is much that is confusing in the facts so far revealed about 

 the two component parts of the alexin. The most difficult fact to 

 explain is the peculiar inactivation of the mid-piece in salt solution, 



55 Michaelis and Skwirsky. Zeitschr. f. Imm., Vol. 4, 1910. 

 66 Skwirsky. Zeitschr. f. Imm., Vol. 5, 1910. 



