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THE CHESTNUT BLIGHT 

 Preliminary Report on Induced Immunity 



By Dr. G. A. Zimmerman, Pennsylvania 



Some thirty-five years ago, when blight killed some of my favorite 

 pears on my father's farm, and spared a Kieffer. I first realized that 

 there was some difference in the reaction of living things to disease, 

 which is now known as immunity. My first actual experience began 

 as a kid when I took some of my father's tobacco, stole away, and 

 tried to play the part of a man. After that I was more or less alert, 

 and, as a student of medicine, the subjects of immunity and internal 

 secretions absorbed much of my spare time and appealed to me so 

 strongly that, even before my graduation, I had begun to make vac- 

 cines and used them in the disj^ensary of the Maryland General Hos- 

 pital in Baltimore. Later I used them in my private practice. During 

 tliis time the chestnut blight raided the country and it was my firm 

 conviction that artificial immunity, or rather induced immunity, might 

 offer a solution for that calamity. I even drew the attention of one 

 of our governors to the subject, who was considerably interested and 

 turned the letter over to some prominent authorities who tabooed the 

 idea and allowed it to die a natural death. In the meantime the chest- 

 nut blight rages. 



Three years ago, when casting an experimental eye around. I made 

 an emulsion of the black aphis, then disturbing the cherry trees. This 

 emulsion I injected into a small tree which I thought was affected 

 with more aphis than any of the others. Forty-eight hours later the 

 new growth on the top of this tree was dead. This convinced me that 

 the material was quickly absorbed, was highly toxic and that the plant 

 reacted to this antigen in a similar way to that of an animal. 



V 



I was now prepared to tackle the chestnut blight. Unfortunately 

 I burned out, and my laboratory with it, about the time I landed in 

 the hospital five years ago, and I had to prevail on some one else to 

 make the serum. I don't know whether my persuasion succeeded or 

 whether Mr. Gravatt felt disposed to help me go ahead and make a 

 fool of myself, but anyway he kindly prepared the basic material 



