1 1 is STUDIES l.\ IMMUNITY. 



fever, contains specific sensitizers, inasmuch as any one of these 

 -era has the property of fixing alexin in the presence of the specific 

 organism against which it was formed; this property is not possessed 

 by any one of the sera under normal conditions. 



Since then I have used the same method* to demonstrate spe- 

 cific sensitizers in the serum of animals which had received in- 

 jections of albuminous substances such as milk, albumin, fibrin- 

 ogen or alien serum. An albuminous solution on the addition 

 of its specific antiserum acquires the property of fixing the alexin. 



The technic employed is as follows: The bacteria or the albumin 

 in question is mixed with a small amount of alexin and the anti- 

 serum in which we are endeavoring to prove the presence of a sen- 

 sit izer. A few hours later sensitized red blood cells are added to 

 this mixture. These cells, which, as we know, are very susceptible 

 to alexin, served to indicate whether the alexin which was added 

 in the first place has remained free or been absorbed by the al- 

 buminous bodies. If the bacteria or the albuminous substance 

 has been sensitized by the serum that is being investigated, it 

 absorbs the alexin and subsequently added corpuscles remain 

 intact, as no free alexin is present. • 



In this communication I also make use of this method, which 

 was first employed by Bordet and myself in 1901, to demonstrate 

 the presence of sensitizers in the serum of animals that have been 

 immunized with various acid-fast bacilli and for the purpose of 

 showing by such sensitizers the relations between saprophytic 

 bacteria and those which are pathogenic either for cold-blooded 

 or warm-blooded animals. 



Very little work has been done with antituberculous sensitizers. 

 Bordet and If have been able to show that guinea-pigs immunized 

 with avian tubercle bacilli form sensitizers which are active against 

 both human and avian tubercle bacilli. 



Dembinski noted in 1904 that rabbits and doves which have re- 

 ceived injections of avian bacilli form sensitizers against these 

 organisms, but no such sensitizers following the injection of 

 human tubercle bacilli. I have questioned certain of this author's 

 conclusions.^ Wassermann and Bruck § have recently employed 



* Page 241. t See p. 462. t See p. 464. 



§ Wassermann and Bruck, Deutsche med. Wochenschr., 1906. 



