l'^() LOCAL TLSSUE REACTIVl'IY 



or two ol his cxjieriinciits there seciii to he a dehiiitely increased 

 reacti\ily when animals were retested alter a week or two. A 

 transitory "desensiti/ation" was induced l)y him by an intrave- 

 nous injection twenty-lom horns or less l)elore the test intrader- 

 mal injections were made. Work on the j)r()l)Iem of desensitiza- 

 tion will he discussed in Clhapter x. It should he jiointed out here 

 that Bmiiet immunized rahhits for short intervals of time and 

 employed non-measmed cjuantities of materials for testing of 

 their imminiity. Moreover, no differentiation was made as to the 

 sensitivity of the rahhits to the phenomenon prior to the experi- 

 ments. As Avas shown in my experiments just described, luider 

 these conditions the state of active acquired immunity coidd have 

 been easily overlooked if, for example, rahhits highly sensitive 

 to the phenomenon ^vere immunized for a short period of time 

 and retested by large doses. On the other hand, prolonged im- 

 munization ^vith graded amounts of materials may induce a stead- 

 fast immunity against 200 and 300 and sometimes 1000 midtiples 

 of the initial dose. Stolyhwo (1935 and 1936) noticed that forty- 

 two days after the elicitation of the phenomencjn the rabbits de- 

 veloped an immunity against moderate doses of the filtrate. In 

 some instances, this immunity lasted as long as ninety-two days. 

 The employment of very large doses could, ho^vever, break the 

 immunity and elicit positive reactions. He also studied the spec- 

 ificity of the active acquired immimity. For this purpose he se- 

 lected rahhits in which the phenomenon had been previously elic- 

 ited with B. typhosus and B. paratyplwsus cidtine filtrates and 

 attempted to reproduce the phenomenon again Avith heterologous 

 and homologous filtrates. These experiments suggested to this 

 author that the elicitation of the first phenomenon induces a 

 resistance of a relative specificity. 



Rabbits in Avhich positive reactions were obtained by Plant 

 (1932) with Spiyoclieta pallida active principles, were retested 

 after various intervals of time. No reactions could l)e elicited in 

 these animals five days after elicitation of the phenomenon, only 

 occasicjnal reactions occurred t^velve days later and five Aveeks 

 later-, they became positive again. Kielano"\vski (1935) and 

 Kielanowski and Selzer (1934't') note the loss of sirsceptiljility of 

 rabbits and sometimes apjjearance of hypersensitiveness a few 

 wrecks follo^ving the elicitation of the phenomenon. 



Michelazzi (i935«) reported that a single intracutaneous in- 

 jection of B. coll filtrate induced a state of local imnuniity to 



