42 STUDIES IN IMMUNITY. 



(c) Guinea-pig No. 1 (340 grams) received 0.2 of a cubic centi- 

 meter of serum "A"; guinea-pig No. 2 (350 grams), 0.2 of a cubic 

 centimeter of serum "B"; control guinea-pig (355 grams). Animals 

 given iV of a culture. Guinea-pig No. 2 and the control died the 

 following afternoon. Guinea-pig No. 1, that had received serum 

 "A," survived. 



It is evident, then, that serum has a higher preventive power than 

 plasma, or, rather, than a transudate caused by venous compression 

 and containing fewer leucocytes than serum. Serum containing 

 the normal number of leucocytes is more preventive than serum in 

 which the leucocytes have been artificially diminished. Although 

 the edema fluid has, to be sure, a distinct preventive property, the 

 data given indicate very clearly the importance of leucocytes in respect 

 to the preventive properties of serum. It is quite possible that during 

 life, under normal conditions, a certain diffusion of preventive 

 substances from the leucocytes may take place, although there is no 

 certainty that the edema produced by a rubber band corresponds 

 at all exactly to the plasma of the blood. 



V. SPECIFICITY OF THE BACTERICIDAL SUBSTANCE IN THE 

 SERUM OF VACCINATED ANIMALS. 



In the group of vibrios there are several bacterial species having 

 similar characters. It is very difficult either by morphology or by 

 cultural characteristics to distinguish the cholera vibrio from the 

 vibrio of Massaouah, the vibrio of Deneke or the vibrio of Finkler. 

 The great importance of finding some means of distinction between 

 these organisms accounts for the careful study that has been made 

 of them. On account of its pathogenic importance and for the 

 value that a positive diagnosis of its presence would have, the 

 cholera vibrio has been particularly well studied in order to deter- 

 mine such characteristics as could be used to separate it from other 

 similar micro-organisms. Most of the attempts at separation of 

 this organism have failed, and it was found that certain properties 

 which were first supposed to be specific were also present in other 

 vibrios. The comma bacillus presents frequent confusing changes; 

 it changes morphologically; it does not always liquefy gelatin with 

 the same rapidity; and its virulence is very changeable and easily 

 lost. The Finkler organism or the Deneke organism, which are 



