64 



from which I completed a serum and began my first injections last 

 year. 



Before proceeding further it is well to understand that any sub- 

 stance, known as an antigen, thrown into the system of any living 

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

 which will digest and destroy it. This excess ferment is the immunis- 

 ing principle in all cases and does not exist until the attack against the 

 cells makes the manufacture of it compulsory. In this they are like 

 the human being. They won't do anything until they are compelled to. 

 Strictly speaking, this means that there is no such thing as "natural 

 immunity." It is all acquired, and every chinquapin or chestnut which 

 has any degree of immunity to the chestnut blight furnishes evidence 

 that some time back through the ages these plants have been attacked. 

 If the active disease gradually stimulated the manufacture of this 

 ferment, it is evident that the products of this disease, which cannot 

 produce the active destruction, will also stimulate the production of this 

 ferment, and it is upon this idea that I am acting. To be more 

 specific, what I am after is to get enough of this defensive ferment in 

 the body of the chestnut tree to either kill the blight germ or hinder 

 its development. Some plants already retard the develojijment, such 

 as the chinquapin, Chinese chestnut and some of the Japanese chest- 

 nuts, but none will hinder its development entirely. In fact, after 

 thirty years I have found that the American chestnut has scarcely 

 enough of this defensive ferment developed to be worth talking about. 

 This power of the defensive ferments of the chestnut to hinder the 

 development of the blight organism is termed "resistance." 



I have found that old people, or old animals, develop this de- 

 fensive ferrnent to a very moderate degree, if at all. Young animals 

 or people usually develop it to a high degree, but once in a while one 

 will be found that cannot be made to develop it by any known means. 

 Presuming this would be the same with the chestnut, I confined myself 

 to young plants. I have observed, however, that the sprouts surround- 

 ing the very large chestnut trees are usually dead. Apparently the 

 power of endurance is not so great as that of the younger trees, many 

 of which still continue to throw out sprouts from the roots. This, I 

 presume, is due, like the old animal, to the inability of their cells to 

 manufacture the protective ferments in sufficient quantity. 



Another thing I have learned in animals is that after every in- 



