many important Truths in Thytology. 107 



French and English, are of this opinion, and call them so. But 

 dissecting progressively, it is impossible tomistake the ingredients. 

 From the birth of plants to their end, from the first of their for- 

 mation to the last, the spirals perf;-.;) but one part, that of 

 proving the strength of the tree, and its cause of motion. — I now 

 therefore turn to my third proposition. 



III. That the Spiral Wire is the Muscle of the Plant. 

 To prove that the spiral wire is the muscle of a plant, and 

 acts on and for the plant exactly as the independent muscle does 

 for the animal body, — I shall first draw up the physical resem- 

 blance, showing in how true and perfect a manner every part 

 suits. In the first place, muscles are to the animal body, the 

 strength of motion. Like the wood of the vegetable, the bone 

 may lay claim to support the figure; but the muscle is the only 

 source of real strength in both. Wherever strength and motion 

 are required, there is the muscle found; and wherever strength and 

 motion are requisite in tlie plant, there the spiral wire is dis- 

 covered. As it is involuntary motion only that can be comyared 

 to the vegetable, it is that only which I refer to in animal's. I 

 showed in my Comparison of animal and vegetable Life*, that the 

 latter had neither brain nor verves, and could not therefore have 

 any voluntary motiun ; but that, to make it amends for this ap- 

 parent privation, it possessed in a very superior degree that in- 

 voluntary motion to be discovered in animals; that motion 

 which is called the vis insita of the muscles, belongs to no other 

 part; which, when the muscle of an animal is completely di- 

 vided from every other ingredient, will convulse it and keep it in 

 a continual agitation for a time, especially if the hght shines 

 on it. This has been called the vis imita of the muscles. The 

 cause of this vis insita in animal nuiscles is unknown ; but in 

 the spiral wire it is certainly light, and moiUure, that act on it; 

 since the moment it is exposed to the light (especially after being 

 detained some time in the dark), its motion is excessive, though 

 perfectly inert before. Nay, I have in my sliders placed an ani- 

 mal muscle in one, and a spiral wire in the other, and they have 

 both on being presented to the light moved much ; but the 

 'ipiral infinitely more than the animal muscle : — still both light 

 Hud moisture seemed to affect each, though in an unequal degree. 

 Thus the cause of motion, the means of strength, to both muscle 

 and spiral wire, both |)ossefising the same vis i«i2/o, who can 

 deny that the spiral is the muscle to the plant? It appears to 

 nic to be so positive a proof as to require no other, since the vis 

 insita is the very sign of the muscle. But I shall not trust to 

 that evidence alone, but prove also that it is the source and 

 * See Pliil. Mag. Aug. 1815, p. 81. 



' cause 



