HAEMOLYSINS. 3 



had been increased, namely, the power to clump 

 the rabbit blood-corpuscles. This so-called agglut- 

 ination of the red cells occurs previous to their solu- 

 tion. The increase in the agglutinating power of 

 the haemolytic serum is a specific one. For if an 

 animal, species A, be treated with blood of species 

 B, the serum derived from A will have acquired 

 an agglutinating power which differs from that of 

 normal serum of A in one very important particular, 

 namely, in that it is specifically increased with 

 respect to the red cells of species B or its nearest 

 biological relatives. 



That normal serum of an unrelated species pos- 

 sesses the power to clump the red cells of many 

 other species had already been shown by Creite 

 and Landois; and this clumping is not to be con- 

 founded with rouleaux formation. However, the 

 single, specific increase of the agglutinating power 

 with respect to a distinct and definite species of 

 red cell by treatment with these cells was first 

 demonstrated by Bordet. 



Nature of Haemolytic Sera Active and Inactive Sera 

 The Two Parts of Haemolysins. This author now 

 turned to a further study of the action of the 

 haemolysins, and was able to show that the sol- 

 vent power of the specific haemolysins depended 

 on the combined action of two constituents of the 

 specific serum. When the fresh haemolytic serum 

 was warmed for half an hour to 55 C., it lost its 

 power. If to this inactive serum a very small 



