4 COLLECTED STUDIES IN IMMUNITY. 



If the immune serum is heated to 56 C., it completely loses its 

 solvent action. The addition of serum of normal animals to this 

 inactivated serum causes it to be reactivated. For this purpose one 

 can use not only normal goat serum but also normal sheep serum, 

 though the latter acts somewhat more feebly. This power of the 

 normal serum to reactivate an inactive immune serum is very readily 

 lost. Even when the serum is kept on ice and protected against 

 light it very soon shows a diminution of its reactivating power. In 

 iiantitative experiments, therefore, the inactive (stable) immune 

 serum should always be reactivated by a perfectly fresh normal 

 serum. 



In haemolysis, as in Pfeiffer's bacteriolysis, we are therefore forced 

 to assume the existence of two substances. One of these, specific 

 and quite resistant (stable), we shall call the immune body, following 

 Pfeiffer's nomenclature. The other, normally present and highly 

 labile (unstable), we shall for the present term addiment. 



Although our results in the main agree with those of Bordet, 

 we must at once call attention to one difference in our observations. 

 As already mentioned, the action of our goat serum on the sheep 

 blood-cells is not preceded by any agglutination. From this we see 

 that the agglutination cannot be considered a preparatory step neces- 

 sary for the hsemolytic action, as Bordet seems to assume. The 

 specific agglutinin has no relation whatever to the ha3molytic 

 immune body. Similarly, according to the views of eminent bacte- 

 riologists, the specific bacteriolytic substances have no relation to 

 the agglutinins. The lysins may exist independently of the agglu- 

 tinins and these again independently of the bacterioloytic substances. 

 The reader is reminded of the interesting observations of Pfeiffer 

 and Kolle. These investigators described an immune serum which 

 was strongly bacteriolytic but which did not at all agglutinate (Cen- 

 tralblatt f. Bakt., 1896, Vol. XX, Nos. 4 and 5). On the other hand, 

 E. Frankel and Otto state that if a young dog be fed on typhoid 

 cultures, the dog's serum will acquire agglutinating but not bacte- 

 riolytic properties. Similarly, if a frog is treated with typhoid bacilli, 

 the frog serum will agglutinate such bacilli. They remain in the 

 lymph sac of the animal, however, not only alive but virulent. (Widal 

 and Sicard, Comptes rend. Soc. de Biol., XI. 27-97). 



Pfeiffer's original theory sought only to explain in general the 

 mode of action of the specific bacteriolysins. It did not concern 

 itself with the questions how or where they originated. It was in 



