IMPROVED,- «j 



of the \^eins are the fame with thofe of the Arteries, 

 only the Mufcular Coat is as thin in all th« Veins 

 as it is in the Capillary Arteries ; the Preffure of 

 the Blood againfl the Sides of the Veins, being lefs 

 , than that againft th-^ Sides of the Arteries. 



In the Vein^ ;:icre is not any Pulfe, becaufe the No Pulfe in 

 Blood is thrown in':o them with a continued Stream, the Veins, 

 and likev/ife becaufe it moves from a narrow Chan- ??^ ^,"^ 

 nel to a wider. The Capillary Veins unite with ^1^ 

 one another, as has been faid of the Capillary 

 Arteries. 



In all the Veins which are perpendicular to the 

 Horizon, (I mean in Horfes ; for in human Bodies 

 the Veins of the Uterus and the roria are ej^ceptcd) 

 there are fmall rvieinbranes or Valves: Sometimes The V.ilves 

 there is only one, fometimes there are two, and -^'^' Scribed, 

 fometimes three, placed together like fo many half 

 Thimbles fluck to the Sides of the Veins, with 

 their Mouths towards the Heart. Thefe Valves 

 are, in the Motion of the Blood towards the Heart, 

 prelTed clofe to the Sides of the Veins ; but if the 

 Blood falls back, it mull fill the Valves ; and they 

 being dillended, flop up the Channel, fo. that lit- 

 tle or no Blood can repafs them. And that this is 

 the Cafe of a Horfe troubled with the Farcin, (com- 

 monly called the Farcy ) appears from the hard 

 knotty Tumours in the Veins, efpecially of the 

 Legs, Thighs, ^c. which Ihew themfelves in this 

 Diilemper. For the Blood is, in fuch Cafe, tOQ 

 vifcous or clammy, and fubjedl confequently to a 

 Lentor^ or Slownefs in Circulation : Therefore, in 

 fupporting its pei^endicular PreiTure, the Veins 

 are more than ordinarily flretched, and the Valves 

 drained accordingly ; infomuch, that they appear 

 plainly through the Skin or Hide. 



Let any one but confider this lafl Piece of Me- 

 chanifm, I mean of the Valves or Flaps, in the 

 Manner as the Leatherit -I^laps in a Pump Box, 

 which are, as I have already faid, defigned by 

 Nature to fuftain the Blood in its perpendicular 



Preflure, 



