INTRODUCTION. XXXI 



action of new matter, such as manures, the carbonic 

 acid in the atmosphere, poisonous agents ; by any 

 circumstance 'which draws matter from its texture ; 

 by vegetable parasites, and animal parasites. In all 

 these respects the pathology of the vegetable is like 

 the pathology of the animal, except that it is less 

 complex, and presents fewer difficulties to investiga- 

 tion. 



The business of a surgeon is essentially locomotive, 

 and his duties are practised over an extensive space. 

 It frequently happens that I have to traverse Lon- 

 don in two or even more directions in a single day, 

 which circumstance has given me abundant oppor- 

 tunities of making my observations in different lo- 

 calities. 



Moreover, during the summer months, I was living 

 at Springfield, Upper Clapton, where I had the ad- 

 vantage of a large garden, wherein were several 

 plots of potatoes, which I was in the habit of observ- 

 ing th^ first thing in the morning, again on my return 

 from London, and frequently the last thing at night. 

 In the neighborhood, moreover, were larger potatoe 

 grounds, where I used to enjoy the air, and study the 

 disease in the evening ; and it has curiously happened, 

 that I have made my observations on the potatoe 

 plant in the same garden in which I conducted the 

 experiments for my former work, on " Electro-Metal- 

 lurgy." 



I must caution my readers against supposing that 

 they will be able to find in a single day all the 



