148 



Scientific Proceedings (67). 



guinea-pig tissues, which is usually ascribed to the presence of the 

 same antigen in sheep cells and guinea-pigs cells. Consequently 

 the latter neutralize the injected hemolysins, instead of anchoring 

 them in unchanged form. If, however, the serum of rabbits 

 immunized against ox red blood cells is used, passive sensitization 

 is invariably induced. 



The mechanism differs somewhat from that of serum anaphy- 

 laxis. As in the latter, indeed, the essential factor is the cellular 

 or anchored antibody. In addition, however, there must be 

 sufficient circulating antibody to break up the alien cell (hemoly- 

 sin), dissolve its protein, and so bring it into intimate contact 

 with the anchored antibody. It is on this account that an animal 

 must be actually partially immunized, so that its blood gives a 

 hemolytic titer, in order to sensitize it. These two factors have 

 been demonstrated by showing that passively sensitized guinea- 

 pigs which have then been thoroughly perfused with normal 

 guinea-pig blood, are no longer sensitive to washed alien red cells, 

 but do succumb to the injection of sensitized cells. Actively 

 sensitized animals react in the same fashion, if the experiments 

 are done at a long interval after primary sensitization, when 

 circulating hemolysin has disappeared. Finally, in all animals 

 dying of red cell anaphylaxis the blood serum is tinged with 

 hemoglobin. As regards controls, it may be said that the injec- 

 tion of sensitized cells, or the simultaneous injection of cells and 

 hemolytic serum has no effect. 



89 (1021) 



The origin of endogenous uric acid. 



By R. L. Stehle. 



[From the Laboratory of Physiological Chemistry, Sheffield 

 Scientific School of Yale University.] 



The source of the endogenous uric acid of the urine has been 

 the cause of much speculation and experimentation for years. 

 The theories that it arises from glandular or muscular activity, 

 however, have claimed most attention. 



Experiments have been conducted on man to determine the 



