XXX INTRODUCTION. 



is accustomed to weigh the various difficulties which 

 arise in the investigation of a complex organic body ; 

 and on that account he is peculiarly suited for the 

 discovery of the cause of an universal malady. The 

 disease in the plant is a death of the vegetable tissue, 

 and the questions of life and death especially pertain 

 to the business of a surgeon. 



The death of a vegetable is referable to causes 

 precisely similar to those which occasion the death of 

 an animal ; and although the embarrassing circum- 

 stances are less numerous in the vegetable than in 

 the animal, yet they are of the same nature, and are 

 to be investigated upon similar principles. It is for 

 this reason that I attempted the inquiry, and I applied 

 a mode of investigation into the cause of the potatoe 

 disease, similar to that which I should have employed 

 in an investigation of the causes of death in the hu- 

 man being, and the result has been the elucidation of 

 the mystery. 



Man is influenced by temperature, light, electricity* 

 barometric pressure, hygrometric state of atmosphere ; 

 by the action of new material as food, morbid poisons, 

 air for respiration ; by anything which draws nour- 

 ishment from the body ; by vegetable parasites, as in 

 the case of scald-head ; by animal parasites, as in the 

 case of tape- worm, pediculi, &c. ; and, last of all, he 

 is influenced by moral impressions, as fear, hope, joy, 

 &c. The vegetable is influenced in a similar man- 

 ner by temperature, light, electricity, barometric 

 pressure, hygrometric state of atmosphere ; by the 



