of different Natures, according to the Power of the 
Will ; which proceed from the Brain and Mafs of 
Blood. Thole from the Brain, he fays, are nitro- 
aenal Particles, and the true Animal Spirits ; and 
thofe from the Blood he call s falmo-fulfthureous $ and 
that the former, being fent by the Nerves, meet the 
latter] in the Mufcle wherein they are fecreted, as was 
faid before, and make the Emotion and Fermentation, 
which is the Caufe of mufcular Morion. 
XXVI. 
As to his Manner of mufcular Motion’s beintr 
O 
brought about, it feems to be inti rely his own In- 
vention : He denies that it can be performed by 
Inflation, either of the mufcular Fibres, or Fibrillar 
fhe latter of which, according to him, are folid Bo- 
dies, and can undergo Contradion no other way 
than by Twilling or Contortioyi } and that thofe nitro- 
aerial Particles arc very fit to affed the Fibrill, ie in - 
that Manner, To prove this, he brings the follow- 
ing Experiment: Let a fmall String of a mufical In- 
flrument be held between the Fingers of each Hand, at 
a confiderable Diflance from each other, over a lighted 
Candle, fo as that it may become {Efficiently heated 
without burning : When throughly hot, it will be per- 
ceived to contrad with a confiderable Force, by twilling 
itfelf $ and, moved from the Candle, will be eafily dis- 
tended again, by untwilling. Thus, fays he, the nitra- 
aerzal Particles iffuing from the Candle are the Caufe of 
the Contradion of the String ; as they are of the Fi - 
brill ie being writhed and fhortened about the mufeu- 
iar Fibres in the Body ; which being by that means 
drawn defer together, the whole Mufcle is fhorten’d. 
This 
