CN THE IRRITABILITY OF VEGETABLES. O^ 



(f of some acrid fluid, either' corrosive or spirituous; then 



" the irritated body regains its former state, and the convul- 



" sions are often repeated, although the impression, which 



. '* is the cause of them, is not renewed. We can sometimes 



" recall these motions when they are finished, by the same 



* e means which at first produced them. This irritability 



" shows itself by the action of a stimulant, which may be 



*' of a very different nature, but always appropriated to the 



" muscle which it ought to move*." In another place he 



says: " We have pushed the analogy between animals and 



*' plants too far. If we understand by irritability the power 



" of being affected by foreign bodies, it will be found in 



" almost all organized bodies; if we understand the volun- 



*' tary command of a muscular force, the analogy subsists 



" no long-erf." 



I am willing to adhere to the definition, which Senne- Volition not 



bier first states, but cannot agree with him in admitting the necessa?ll y 



„ T -, • ■. i , i-.,- • • connected with 



latter; tor 1 do not consider that volition in every instance irritability. 



is connected with irritability. We know well, that the sen- 

 sible iris often contracts and dilates without out knowledge 

 of it. Here then volition, or a voluntary command of a 

 muscular power, is out of the question ; yet none will deny, 

 but that the iris is one of the most irritable parts of the ani- 

 mal body. We also sometimes observe, that the motions of 

 the iris continue, when all voluntary power is at the mo- 

 ment suspended, as in certain cases of concussion of the 

 brain, &c. We know also, that the most important func- 

 tions in the animal system are carried on quite independent 

 of the will. The heart for instance is continually acting, 

 yet we are unconscious of it. There are many other mus- 

 cles &c, which also act independent of the will, as the diaph- 

 ragm, the muscles of the intestines, and even at times the 

 sphincter muscles, &c. Hence some of them have been de- 

 nominated involuntary muscles. We have now seen then, 

 that motions go on in the living animal system without the 

 concurrence of the will, and yet that the parts are highly ir- 

 ritable. Bearing this idea in mind, cannot we conceive, that 



* Sennebier's Physiologie Vegetale, tome Y, p. 87. 

 t Pbvsiol. Vegetal, tome V, page 120., 



the 



