( 3 1 9 ) 
By which it appears that the Proportion of the 
Blood-Veffels in their compleateft Contraction, to 
themfelves in a State of Extenfion, and to the Nerves 
at their conftant and natural Length, is nearly as 5 
to 8 ; or, which is the fame thing, any given Seftion 
of a Blood-Veffel, cut out and left to itfelf, is capa- 
ble of contra&ing, fo as to lofe f Parts of its Length. 
But though this Experiment may fuffice for efti- 
mating the Elafticity of the Blood-Veffels in general, 
yet it is not to be doubted, but the Degree of their 
Strength and Elafticity may differ a little more or lefs 
in Animals of different Species, and Individuals of 
the fame Species* nay even in the fame Individual at 
different Stages of Life 5 butthefe Differences are not 
material to my prefent Purpofe, which is only to 
fhew, that the Nerves are not elaftick, and that the 
Blood* Veffels are fo to a very confiderable Degree. 
INFERENCES from thefe E X P E* 
RIMENfS .. 
Thetwo firft Experiments fhew, that the Brain and 
Nerves contribute to mufcular Motion, and that to a 
very high Degree. 
The third Experiment makes it as plain, that what 
they contribute in mufcular Motion, cannot arife from, 
or be owing to Elafticity, which they have not. 
What remains therefore but to conclude, that the 
Aftion of the Nerves in mufcular Motion, is owing 
to the Fluid they contain, by whatever Name we may 
choofe to call it* 
To fortify this Conclufion, let us confider, that we 
can have no other Evidence of the Exiftence of that 
invifible 
