Chap. III. The Anatomy of a HORSE. 27 



each of them Valves, for the better Performance of their 

 feveral Fundions ; to wit, the Vena Cava, which enters 

 into the right Vefitricle^ has three, call'd Trienfpides, from 

 their triangular Figure. They are plac'd at the bottom 

 of the Heart, where the faid Vein enters, and pointing in- 

 wards, a free admittance is given to the Blood, which goes 

 into the Heart, but none of it can return back again the 

 fame Way. The Vena Arterioja, or Pulmonary Artery, 

 which carries the Blood from the fame Ventricle to the 

 Lungs, has alfo three Valves, call'd Sigmoidea, from the 

 Rcfemblance they bear to the old Greek Sigma, thefe look 

 from within outwards, by w'hich Means they hinder the 

 Blood from returning back again into the Heart. 



To the Arteria Venojd, or Pulmonary Vein, which re- 

 turns the Blood from the Lungs into the left Ventricle, be- 

 longs two Valves, called Mitrales, from the Refemblance 

 tliey bear to a Miter. Thefe have the fame Office as thofe 

 of the Cava above defcribed : And the three Valves of the 

 Mrta, or great Artery, called Semilwiares^ from their be- 

 ing fofliion'd like fo many Half- moons, have the fame 

 Office as thofe of the Arteria Piilmonaris. 



But laftly, there belong alfo to the Heart jf j - j 

 two Auricle?^ or Earlets, from the Refem- ^ ^^^ "' 

 blance they bears to Ears, being feated like two Purfes on 

 each Side of its Bafis. Thefe Earlets have their DiaJloU 

 and Syflole, like unto the Heart, only with this difference, 

 that when the Heart is contraded, the Earlets are dilated ; 

 and when the Heart is dilated, the Earlets are contracted ; 

 the Reafon is, becaufe they receive the Blood from the 

 Cava and Pulmonary Veins, fo that as they empty them- 

 felves into the Heart, it forthwith becomes dilated ; and 

 when the Heart is contrafted, they muft of Confequenc£ 

 be filled, the Courfe of the venal Blood being, at that 

 Interval, intercepted. 



The Ufe of the Auricles is to meafure ^^eir U/e. 

 out the Blood in certain Proportions, before 

 it enters the Heart, iell, rulhing in with too great an Impe- 

 tuofuy, it might not only caufe the Valves to be violated, 

 but occafion a Suffocation in the Heart itfelf whereby the 

 vital Faculty might be quite deftroy'd. 



§. III. Of the Windpipe and Lungs, 

 The Lungs are the chief Inftruments of i:he Lungs, 

 breathing, they fill up the gre^teft P^rt of the 



Cavitf 



