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FURTHER EXPERIMENTS IN INDUCED IMMUNITY TO 



CHESTNUT BLIGHT 

 By Dr. G. A. Zimmerman, Piketown, Pa. 



It will be recalled that about a year ago, before this scientific body, 

 I presented a preliminary report on "Induced Immunity to Chestnut 

 Blight." I presented this subject as ctearly as I knew how, and in 

 the best English that I could command, and it seems that I have been 

 misunderstood. Judging from the reports and the correspondence 

 which I have received one would be inclined to think that I presented 

 this matter as a settled proposition. In offering this second report, I 

 wish it to be entirely clear to every one that my work is experimental 

 and although I have not seen fit so far to change my past ideas and 

 convictions, I reserve the right to reverse myself at any future time that 

 a clearer vision makes that necessity imperative. There is a lot of dif- 

 ference between my ideis, convictions and preliminary experiences, 

 and proved, conclusive, scientific facts. With the above clearly in 

 mind, let me elaborate on my paper of last year. 



In a previous report I used the term serum. This being vague and 

 meaningless, I am substituting the term "endothic antigen" in the 

 present paper. It will be recalled that last year I defined an antigen 

 as "Any substance which when thrown into the system of any living 

 body, will either kill the cells, or they will manufacture a ferment 

 which will destroy it." This resultant defensive ferment is known as 

 as an antibody. It is the thing — nobody knows just what — that 

 enables any living substance to recover from disease and renders it 

 immune. Wlien once developed it is inheritable. Otherwise the 

 Chinese seedling chestnut would be no more nearly immune to blight 

 than an American seedling. 



The ability of plants and animals to manufacture this defensive 

 ferment is variable, depending probably on the activity of the cells, 

 the age and activity of the antigen, the rapidity with which the antigen 

 enters, and, in plant life, the time of the year, and also undoubtedly 

 other factors. Every plant being a unit of its own, entirely independent 

 of others, it is only natural that we should find great variation in the 

 degree of immunity the various species and varieties of chestnut hold 



