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to Endothia parasitica ,and with which variation everyone is familiar. 

 Our medical friends present will recall what we know as generally 

 toxic conditions, like typhoid, diphtheria, and others in which the 

 trouble is largely local, as acne, tuberculosis, and leprosy. We have 

 the same condition in plant life. The generally toxic conditions either 

 immunize quickly, or produce death with the same rapidity, while the 

 locally toxic conditions are just the reverse. The chestnut blight is a 

 locally toxic condition, and were it not for the fact that it goes around 

 the tree instead of lengthwise, the tree would linger along for many 

 years without succumbing. It likewise immunizes slowly. On the other 

 hand the aphis infection causes a generally toxic condition, corre- 

 sponding in a way to typhoid, diphtheria and others, and therefore 

 immunizes quickly. It usually does not produce death unless the in- 

 fection is very severe, except in the new growth, although I have seen 

 small cherry trees killed outright in one season. Most of us, I sup- 

 pose, have observed that a tree badly infected with aphis one season 

 is rarely badly affected the following summer, therefore requiring only 

 a relatively short time to immunize. I only mention this as a matter 

 of interest. 



In view of the fact that nobody knows just what takes place be- 

 yond the inner gates of the cells of living organism, a man who un- 

 dertakes to deal with these conditions must of necessity be possessed 

 with certain faculties in order to obtain maximum results. These quali- 

 fications I have roughly stated as follows : 



One must first have an eye that can see into the future ; 



An antigen that is active against the target aimed at; 



An inexhaustible patience and persistence, and confidence — such as 

 is necessary in any undertaking. 



To illustrate just what I mean: During the past year I got hold 

 of an inactive antigen ; one that not only did no good but harm, and 

 plenty of it. A bombshell was exploded in my experimental field. I 

 was stampeded, dumfounded. If I had not had an eye that could 

 see into the future, and backed up with experience, I should have been 

 defeated right there. However, I had a feeling that something was 

 wrong. I did not know what. I immdiately prepared another antigen, 

 used it bravely, and turn'^d the tide just in time to save two of my most 



