366 PROTEIN POISONS 



are detected in the dialysate by the biuret test. First, it 

 was shown that the serum of normal guinea-pigs with or 

 without mixture with horse serum does not supply biuret 

 bodies. After guinea-pigs had been sensitized to horse 

 serum for six days, then for the first time serum obtained 

 from them and mixed with horse serum and the mixture 

 dialysed, did the biuret test, when applied to the dialysate, 

 prove positive. This does not mean, as we take it, that 

 the formation of the specific ferment begins on the sixth 

 day after the injection of the sensitizer. It means that 

 with the amount of the sensitizer employed, the specific 

 ferment had accumulated sufficiently and was efficient 

 enough when brought into contact with horse serum in vitro 

 to digest it enough to show its action by the biuret test when 

 applied to the dialysate. The serum of sensitized animals 

 continues to digest the homologous protein (that to which 

 the sensitization is due) up to about the thirtieth day. 

 This does not mean that the formation of the ferment 

 ceases after this time. We know that this is not the case, 

 because Rosenau and Anderson have shown that guinea- 

 pigs sensitized to horse serum remain in this condition for 

 two years at least, and probably throughout life. This is 

 an important point and one which H. Pfeiffer nowhere 

 discusses, so far as we can find, although it has been brought 

 out by his work more prominently than by anyone else. 

 In order that it may be understood, we will try to state it 

 plainly. Guinea-pigs sensitized to horse serum furnish, 

 from about the sixth to about the thirtieth day, serum 

 which in vitro digests horse serum, as is shown by the forma- 

 tion of diffusible biuret bodies. After the thirtieth day or 

 thereabouts, the serum of the sensitized animal no longer 

 has this digestive action on horse serum in vitro; at least 

 such action is not demonstrable. And yet the guinea-pig 

 remains sensitive to horse serum. This, in our opinion, is 

 due to the fact that certain fixed cells in the animal body 

 remain sensitive and responsive to reinjection long after 

 the leukocytes lose their sensitization. Pfeiffer and Jarisch 

 found that in the so-called antianaphylatic state the blood- 



