I 



a Comparison between Animal and Feget able Life. 85 



stituted) at all join to the line of life, or form any connexion 

 with it. How then can will be announced or executed F 



There can therefore be no volition in plants, and they can 

 only be a piece of living mechanism. No person who has seen 

 and dissected a plant killed by electricihj, can doubt whicli is 

 the line of life, since this line is directly marked from the root: 

 to everv fibre, and turned completely black in a moment. 



I shall now turn to the animal and vegetable muscle. And 

 here the strongest yimilitude is to be discovered; since it is the 

 only part tliat in boih beings can be said to move by involuntary' 

 muiion or vis insila. It is well knovi^n that in the human body 

 there are three sorts of motion; the voluntary, the involuntary, 

 and the mixed : but the first two will serve our purpose here. 

 The first is caused bv the will, enforced by the nerve, and ex- 

 ecuted by the miisch ; but the last is spontaneous, proceeds from 

 the muscle alone, the cause unknown. It remains often in the 

 muscle after death, and, after it is divided from the brain, even 

 exercises its full 'r^rce in this situation. The human muscle 

 forms part of the flesh ; it consists of two parts, the wide (which 

 alone is active), and the thin shining extremity called the ten^ 

 don. The only purpose of the last is to fix the muscle to the 

 moveable bones, which it does with a force not to be conceived 

 but by feeling it. Thev are thus fastened in a concentrated man- 

 ner, in which a greater power is permitted to act, as labours are 

 assisted by ropes in moving weighty bodies ; each muscle con-^ 

 tracts both ends towards the centre, v/hich serving as a fixed 

 point, draws the bones with it. The wide part of the muscle is 

 the moving part, and is most curiously formed. The muscles diffei; 

 in the number of their cases, some animal muscles have two, 

 or even three ; but the vegetable never but one. In the human 

 muscle a number of long, soft, fleshy fibres are seen inclosing 

 many bundles of hair-like figures, which are the nerves, and 

 which split without end. They appear to me to pass through 

 every part of the muscle, case and all; when the muscle is quite 

 fresh, they seem to move with Ight and moisture if suddenly 

 applied. But I am not sure nf this, having but o?ice been able 

 to get them fresh enough for this examination. It is difficult to 

 discover how solid tiie nerves are, since they contract at the end 

 the moment they are cut, "and with such instantaneous effect, 

 that tliough I have divided them with the microscope at mv eye, 

 I could not catch a view up the pipe. There is no part of the 

 body which may be properly called fleshy (and which is in 

 truth the muscle) which is not penetrated in every direction by 

 7iervvus fibres ; their sensibility pervades the whnle muscular sub- 

 stance, even its smallest ]>ortions ; and though they appear not to 

 move themselve<v, yet they are supposed to be by some means 



F3 ' the 



