IMMUNITY REACTIONS WITH AMCEB^. 293 



■In, one instance in Table IV it will be noted that lysis of the amoebae 

 failed to occur in, the 1 to 2 dilution of serum heated at 60° C. An 

 emrdsion was used which was unusually rich in amcebse and, although 

 the differences were well marked after the preparations had stood for 18 

 hours, yet the amoeba did iLbtt entirely disappear until after 24 hours. 

 These results might be taken as indicating that exposure to a temperature 

 of 60° C/for one hour represents about tlie minimum time which would 

 be effective in producing this change in the serum. Perhaps a more mo- 

 derate heating might have inactivated the immune serum without pro- 

 ducing this change which renders normal serum active. Although it 

 is definitely shown that the immune serum is active after heating yet the 

 controls with normal serum show that it does not necessarily follow that 

 the imfhune bodies are thermostable or that they do not consist of 

 amboceptor and complement. No a,ttempt was made to work out the 

 mechanism of this action of the heated normal serum. It is possible, of 

 course, that it does not act directly upon the amcebas, but affects them 

 secondarily through a primary action on the bacteria; for example, the 

 bacterial products formed in heated serum may be different from those in 

 unheated serum. Apriori, however, the simplest explanation is that of a 

 direct action upon the amoebse. There is one instance in which heated 

 normal serum can be shown to have a definite action on animal cells : 



This phenomenon, which may be somewhat analogous to the reaction, with 

 amoebse, can be demonstrated with red blood corpuscles'' when heated normal 

 serum develops the property of causing marked rouleaux formation of red corpus- 

 cles suspended in salt solution. The degree of heating which is required and 

 the activity of the serum correspond rather closely to the conditions pertaining 

 to amoebae; thus, serum after exposure to 60° C. for 1 hour is effective in producing 

 rouleaux in a final dilution. of 1 to 4, but not in 1 to 6; normal serum after 

 the same treatment is active toward amoebae in 1 to 2 but not in 1 to 5 dilution. 

 It may be noted that this action of heated sera in causing rouleaux formation 

 is apparently only an increase of a normal characteristic of unheated sera. Simi- 

 larly, it can be shown that although amoehse grow well in a 1 to 2 dilution of 

 normal rabbit serum, yet they are destroyed in undiluted normal serum, or in a 

 1 to 2 dilution of heated normal serum. 



BIOLOGIC RELATIONSHIP BETWEEN THE DIFFERENT CULTURES OF AMCEB^. 



The serum reactions with the 2 cultures of amoebse obtained from 

 saprophytic sources were compared with 2 cultures obtained from the 

 intestinal tract to determine their indentity or non-indentity as tested 

 by biologic methods. Eabbits were immunized in a similar manner to 



term lysin is seldom applied to immunity reactions with protozoa. Rossle(8) 

 observed that instead of lytic properties, cytotoxic sera often possess a paralyzing 

 action; the examples cited are the spermotoxic sera, and the anti-sera against 

 epithelium and against paramoecia. 



^ Bull. Johns Hopkins Hosp. (1908), 19, 271. 



