152 VITALITY, HOW AFFECTED [BOOK u. 



poisons on animals. The gases which rank as irritants in 

 relation to animals seem to act locally on vegetables, destroy- 

 ing first the parts least plentifully supplied with moisture. 

 The narcotic gases, including under that term those that 

 act on the nervous system of animals, destroy vegetable life 

 by attacking it throughout the whole plant at once. The 

 former, probably, act by abstracting the moisture of the 

 leaves; the latter, by some unknown influence on their 

 vitality. The former seem to have upon vegetables none 

 of that sympathetic influence upon general life, which in 

 animals follows so remarkably injuries inflicted by local 

 irritants." 



A similar result was arrived at by Macaire, whose experi- 

 ments are recorded in the Bihliotheque Universelle,TLxxi. 244., 

 and which appear of sufficient importance to be detailed at 

 length. 



The first plant used was the Berberis vulgaris. The six 

 stamina of the flowers of this plant have the property of 

 rapidly approaching the pistil, when touched by the point of 

 an instrument. The motion occurs at the base of the stamens. 

 When cold, the motion is sometimes retarded. When put 

 into water or solution of gum, the flowers may be preserved 

 many days, possessing their irritability. The petals and 

 stamens close at night to open again in the morning. Putting 

 the stem of this plant into dilute prussic acid for four hours, 

 occasioned the loss of the contractile property by irritation ; 

 the articulation became flexible, and might be inclined in 

 any direction by the instrument. The leaves had scarcely 

 begun to fade. On placing the expanded flowers on the 

 prussic acid, the same effect took place, but much more 

 rapidly. The experiment being repeated with an aqueous 

 solution of opium, a similar effect was produced in nine hours. 



Dilute solutions of oxide of arsenic and arseniate of potash 

 were used : the stamens lost the power of approaching the 

 pistil ; but they were stiff, hard, withdrawn backwards, and 

 could not have their direction altered without fracture. It 

 seemed like an irritation, or a vegetable inflammation. Solu- 

 tion of corrosive sublimate more slowly produced the same 

 effects. 



