ANTIGENS, HAPTENS, ANTIBODIES, ETC. 435 



of these fractions alone was active, but on mixing them 

 the activity was restored. The two fractions were called 

 mid-piece and end-piece respectively, because it was 

 found that the albumin (end-piece) was not taken up by 

 sensitised red blood corpuscles unless the globulin mid- 

 piece had first been adsorbed. Although the mid-piece 

 is adsorbed in the absence of the end-piece, it cannot 

 induce lysis until the latter is also adsorbed. In Ehrlich's 

 terminology the mid-piece carries the haptophore group 

 and the end-piece the ergophore group. 



Liefmann split complement into mid-piece and end- 

 piece by diluting the serum ten times with distilled water 

 and passing carbon dioxide through the chilled solution, 

 whereupon the mid-piece (euglobulin, with some pseudo- 

 globulin) was precipitated. He showed that the mid-piece 

 was adsorbed in the Wasserman reaction but not the 

 end-piece, which is left quantitatively in solution, and 

 confirmed the finding that both mid-piece and end- 

 piece are necessary for hsemolysis. Both mid-piece 

 and end-piece are heat labile and can be adsorbed by 

 kaolin. 



In 1907 it had been shown that the complementary 

 power of a serum was removed by treatment with yeast, 

 and in 1914 Coca showed that the component adsorbed 

 by yeast was heat stable and that adsorption by yeast 

 leaves the mid-piece and end-piece in solution. Thus 

 three factors are present in complement, two heat labile, 

 the mid-piece and end-piece, and one, the " third com- 

 ponent," heat stable. Ritz, in 1912, had also elicited the 

 presence in complement of a heat stable third component 

 which was inactivated by cobra venom. Whitehead, 

 Gordon and Wormall in 1925 took the problem a step 

 further when they showed that zymin (a preparation of 

 acetone dried yeast) is more effective than fresh yeast for 

 adsorbing the third component ; by examining the effect 

 of zymin on separated end-piece and mid-j^iece they 

 sliowed tliat almost all tlie third component was associated 



