c ) 
Opinion, clifcover likiwife the Blood running thro’ thofe 
Valves : and again if there are Valves in the aforemen- 
tioned Veins of the Arm or Hand, we fbould not be 
able by prefling thofe Veins with the Finger to drive 
the Blood back again, which notwithftanding’ is often 
done. 
Moreover, if there were Valves in the Veins that lie 
^ in the Skin expos’d to our fight, there wou’d, in my O- 
' pinion, a great many Inconveniencies arife therefrom ; 
for if a Blow or Thrull: were-made upon that part 
where the Valve lies, the Blood would not be able to 
retire back, by which means the Valve or even the Vein 
it felf might burft : whereas, if there are no Valves, the 
Blood can eafily retreat upwards or downwards in the 
Veins, as we, in Faff, obferve of thofe Veins that run 
on both Tides in the Tail-Fins of an Eel, which d© not 
unite in one greater Vein where a Valve is, at lead: as far 
we coil’d- follow thofe Veins with our Eyes. 
Having thus far'eommitted thefe my Obfervations to 
Papers, 1 confidered with my felf, whether I might not 
have fomething of this nature lying by me, having for- 
merly confider’d this Subjefl; of Eels j and I find amongft 
other Papers, thefe that follow. . 
In the. Month of September 1706, having opened an 
Eel, and ,taken out the Guts, the Diameter or thicknefs 
of which was about an Inch and a half ; and having alfo 
laid open the Heart, I coifd not dilcover that part 
which receives the Blood out of the Great Vein in oiv 
der to bring it into the Heart. 
But to^the end that I might better difeover that part, 
I prepared a little Glafs-Tube, and put it into the great 
Vein at a. little didance from the Heart, and then blew 
fome Air into the faid Vein, as much as might take up 
the fpace of about half a Pea : this. Air pafs’d- thro’ the 
Great Vein into a little Bladder that lay on the fide of 
the Heart, the like of which I had never before obferr 
ved 
