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Scientific Proceedings (53). 



so-called "midpiece" and the other which remains in the albumin 

 fraction, the so-called "endpiece." Neither of these can produce 

 hemolysis of sensitized cells alone. Together they functionate. 

 The globulin fraction can be bound to sensitized cells, forming the 

 so-called " persensitized cells" which are now hemolyzable by the 

 endpiece alone. The albumen fraction does not become attached 

 or fixed to the sensitized cells except in the presence of the globulin 

 fraction. (The terms midpiece and endpiece are used for the sake 

 of clearness since they are terms which have become etablished in 

 the German literature. Owing to studies which are being made 

 by Mr. Maltaner in this laboratory we feel that a definite nomen- 

 clature which assumes an intermediate function of the globulin, 

 fraction, is premature.) 



In experiments in which alexin fractions, produced by both 

 the method of Ferrata and by that of Sachs and Altmann, were 

 exposed to union with precipitates, formed in mixtures of beef 

 serum and its antiserum, we have found that the conditions which 

 prevail are entirely analogous to those which govern the attach- 

 ment of the alexin fractions to the sensitized cells. A specific 

 precipitate may fix the globulin fraction (midpiece) alone. It 

 may fix the albumin fraction (endpiece) in the presence of the 

 globulin fraction. It does not however, fix the albumin fraction 

 (endpiece) by itself. The experiments were in every case con- 

 trolled by titrations of the alexin fractions and the whole alexin 

 in tubes set up parallel with the main experiment. 



The writer believes that these results have considerable 

 theoretical importance in bearing out his previously expressed 

 view that the " precipitin " may be regarded as a protein sensitizer, 

 the fact of visible precipitation being a merely secondary occur- 

 rence due to the union of two colloids under conditions of quantita- 

 tive relations and environment which favor precipitation. 



