Microscopical Essays. 



It may alfo be further obferved, that as we fee that the motions 

 of the limbs, Sec. of the larger animals are produced by the me- 

 cnanical conilruction of the body, ana the action of the foul 

 thereon, and are forced by the ocular demonllration which arifes 

 from anatomical chiiettion, to acknowledge this median m which 

 is adapted to produce the various motions me cefTary to the animal ; 

 and as when we have recourfe to the micrOfcope, we find thole 

 pieces which had appeared to the naked eye as the primary me- 

 chanical caufes of the particular motions, to confift themfelves of 

 leffer parts, which are the caufes of motion, extenfion,. Sec. in 

 the larger; when the ftruclure c n therefore be traced no fur- 

 ther by the eye or glaffes, we have no right to conclude, that 

 the parts which are invihble are not equally the fubjecl of me- 

 chanifm : for this would be only to affert in other words, that a 

 thing may ex iff becaufe we fee and feel it, and have no exigence 

 when it is not the object of our fenfes. 



The fame train of reafoning may be applied to microfcopic in- 

 fects and animalcula ; we fee diem move, but becaufe the mufcles 

 and members which occafion thefe motions are invihble, mall we 

 infer that they have not mufcles, with organs appropriated to the 

 motion of the whole and it's parts? To fay that they ex id not, 

 becaufe we cannot perceive them, would not be a rational con- 

 clufion. Our fenfes are indeed given us, that we may compre- 

 hend fome effects ; but then we have alfo a mind with reafon 

 bellowed upon us, that from the things which we do perceive 

 with our fenfes, we may deduce the nature of thofe causes and 

 effects which are imperceptible to the corporeal eye, 



MefTrs, 



