[ 34 ] 
ment of the Particles compofmg the main Subfiance 
of an animal Fibre, and of its Conftru&ion. 
Now it is no difficult Matter to overturn this 
Syflem, fince there are two principal Objections to 
be made to it, which prevent the Trouble of any fur- 
ther Confideration. The firft is, That this abfolutely 
is not the Structure of a mufcular Fibre, as we ffiali 
make it appear in the following Lecture: And, fe- 
condly, There is a great Abfurdity in the Compari- 
fon he makes between the A&ion of a Syringe and 
its Embolus , and that of a flexile fibrous Thread : 
For, as it is neceffary, in the Action of that Inftru- 
ment, that its Sides ffiould be inflexible, hard, and 
able to bear the exceffive Force of Su&ion in the 
Retradlion of the Embolus , and the Force of the Air 
in its Repulfion, with how little Propriety can this 
minute fupple Fibre of a Mufcle be faid to be capa- 
ble of a like A&ion, or fuch a Wedge-like Con- 
ftru&ion as this Author thinks applicable to it. 
When, in mechanical Reafoning, we find it necef- 
fary to illuftrate an Opinion by a Companion, there 
ought to be a true Similarity of Structure in the Ob- 
jects whofe A&ions are to be compared 5 otherwife it 
would be altogether as prudent to liken a human 
Blood veffel to a Blunderbufs. 
XLIV. 
Monro. The ingenious ProfefTor * Monro , of Edin- 
burgh, fuppofes the nervous Fluid to be 
an extreme fluid laponaceous Water, flowing in a 
“ con- 
* Anatomy of human Bones and Nerves, p. 29. of the latter. 
