MECHANICAL AND IMMfiCHANICAL, &C. 45 



CHAPTER VII. 



♦?P THE MECHANICAL AND IMMECHANICAL PARTS AND FUNC- 

 TIONS OF ANIMALS AND VEGETABLES. 



It is not that every part of an animal or vegetable has 

 not proceeded from a contriving mind; or that every part 

 is not constructed with a view to its proper end and pur- 

 pose, according to the laws belonging to, and governing, 

 the substance or the action made use of in that part ; or 

 that each part is not so constructed, as to effectuate its 

 purpose whilst it operates according to these laws ; but it 

 is, because the laws themselves are not in all cases equal- 

 ly understood ; or, what amounts to nearly the same thing, 

 or not equally exemplified in more simple processes, and 

 more simple machines ; that we lay down the distinction, 

 here proposed, between the mechanical parts, and other 

 parts, of animals and vegetables. 



For instance; the principle of muscular motion, viz. 

 upon what cause the swelling of the belly of the muscle, 

 and consequent contraction of its tendons, either by an 

 act of the will or by involuntary irritation, depends, is 

 wholly unknown to us. The substance employed, whether 

 it be fluid, gaseous, elastic, electrical, or none of these, or 

 nothing resembling ttiese, is also unknown to us ; of course 

 the laws belonging to that substance, and which regulate 

 its acti(tn, are unknown to us. We see nothing similar 

 to this contraction in any machine which we can make, 

 or any process which we can execute. So far (it is con- 

 fessed) we are in ignorance; but no farther. This power 

 and principle, from whatever cause it proceeds, being as- 

 sumed, the collocation of the fibres to receive the princi- 

 ple, the disposition of the muscle for the use and applica- 

 tion of the power, is mechanical; and is as intelligible as 

 the adjustment of the wires and strings b} which a puppet 

 is moved. We see, therefore, as far as respects the sub- 

 ject before us, what is not mechanical in the animal frame^ 

 and what is. The nervous influence (for we are often 

 obliged to give names to things which we know little 

 about) — I say the nervous influence, by which the belly 

 or middle of the muscle is swelled, is not mechanical. 

 The utility of the effect we perceive : the means, or the 

 preparation of means, by which it is produced, we do not. 

 But obscurity as to the origin of muscular motion brings 

 £ 3 



