ns trument, neither is it a simple power; but the 

 result of the mutual operation of the instruments 

 and rudiments on one another a result, which 

 varies as the operations vary, and which often, 

 from small changes and obstructions, ceases alto- 

 gether. When our elementary books inform us, 

 that the vital power in one place produces from 

 the blood the fibres of the muscle ; in another, a 

 bone ; in a third, the medulla of the brain ; and 

 in another again, certain humours, which are des- 

 tined to be carried of; we know after this expla- 

 nation as little as we knew before. 



This unknown cause of the phenomena of life 

 is principally lodged in a certain part of the Ani- 

 mal Body, viz. in the nervous system, the very 

 operation of which it constitutes. The brain and 

 the nerves determine altogether the chemical 

 processes which occur within the body : and al- 

 though it cannot be denied that the exercise of 

 their functions tends to produce chemical effects ; 

 yet we are constrained to confess, that the che- 

 mical operations therein are so far beyond our 

 reach, that they entirely escape all our observa- 

 tions. Our deepest chemical researches, and the 

 finest discoveries of later times, give us no in- 

 formation on this subject. Nothing 1 of what Che* 



B 3 



