Chap. III. The An^omy of aWOKSV.. ij 



each of them Valves, for the better Performance of their 

 feveral Fundions j to wit, the Vena Cava^ which enters 

 into the right Ve?itricle^ has three, call'd Triefifpides, 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 rione of it can return back again the 

 fame Way. The Vena Arter'ioja^ or Pulmonary Artery, 

 which carries the Blood from the fame Ventricle to the 

 Lungs, has alio three Valves, call'd Signmdece, from the 

 Refemblance they bear to the old Greek Sigma, thefe look, 

 from within outwards, by which Means they hinder the 

 Blood from returning back again into the Heart. 



To the Artena Venofa^ or Pulmonary Vein, which re- 

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

 longs two Valves, called M'ltraks^ from the Refemblance 

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

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

 jiorta^ or great Artery, called Semilunarei, from their be- 

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

 Office as thofe of the Arteria Pulmonaris. 



But laftly, there belong alfo to the Heart j^^ Auricles 

 two Auricles^ or Earlets, from the Refem- 

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

 each Side of its Balis. Thefe Earlets have their Diajlole 

 and Syjiole^ like unto the Heart, only M'ith this difference, 

 that when the Heart is contracted, 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 contradled, they muft of Confequence 

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

 Interval, intercepted. 



The Ufe of the Auricles is to meafure ^^^'^ Ufi' 

 out the Blood in certain Proportions, before 

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

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

 but occafion a Suffocation in the Heart itfeif whereby the 

 vital Faculty might be quite dellroy'd, 



§. HI. Of the IVindpipe and Lungs. 

 T\\t Lungs fiXe the chief Inftruments of the Lungs. 

 breathing, they fill up the greateft Part of the 



Cavity 



