to be contraded ; whilft, at the fame Inftant, the 
Valve of the latter is fhut, in order to hinder their 
Flowing-out again, that the Mnfcle may be fwell’d. 
By this Swelling the Situation of the Parts being al- 
tered, the Valve opens again, (the other Valve being 
now fhut) and the Spirits flow freely back again to 
the Mufcie to be contraded. 
VII. 
Cartejins s * Opinion was not very different from 
this : He fuppofes “ Several Openings in each Muf- 
“ cle, through which the Spirits may pafs from one 
<c into the other; which are fo difpofed, that, when 
“ the Spirits, which come from the Brain towards 
<£ one Mufcie, have a little more Force than thofe 
which go towards another, they open all the Ori- 
u flees through which the Spirits of the other Mufcie 
“ can pafs into this; and, at the fame time, fhut up 
<£ all thofe by which the Spirits of this may pafs into 
“ the other ; whereby all the Spirits, contained be- 
<c fore in both Mufcles, fwiftly pafs into one of them, 
and fo fwell and contrad it, while the other re- 
ie mains relax’d and extended.” 
VIII. 
Thcfe Tubes, Valves, and Openings, are merely 
conjedural } having never been found by any Ana- 
tomift, and being only Children of the Imagination 
of fome Philofophers, produced to ferve their uncer- 
tain Hypothecs. Nor, indeed, would it be a difficult 
Matter 
* De Tajfion. Anim. Part i. Artie. II. 
