2 5 The Anatomy of a HORSE. Chap. IIL 



flefhy Fibres, which, towards the Top, take their Diredti- 

 on Ipirally, like the Contortion of a Snail's Shell. 



It is faid to have a twofold Motion, which by Anato- 

 mifts is call'd ^ydole and Diaftsle ; or, in other Words, 

 its Contradion, when its Top is drawn towards its Bafis 

 or Bottom, for the Expulfion of the Blood into the Arte- 

 nes ; and its Dilation, when it is fiU'd with Blood from 

 the Veins. As often as we feel the Pulfe beat, fo often is 

 the Heart contrafted ; it being the Contraction or Syftok 

 of the Heart, which communicates that Vibration or Pul- 

 iation to all the Arteries. 



The Heart, befides its Pericardium above-defcrib'd, 

 hath two Membranes, one that covers all its outfide, which 

 it derives from the outer Coat of the great Artery, and an- 

 other which lines it through all its infide, which proceeds 

 from the inner Coat of the faid Veflel. It is ftored with 

 Fat towards its Bottom, which keeps it moift and glib, as 

 the Water in \hQ Pericardium does the reft of its Subftance. 

 7*^ Ve/Teb Befides the large Vellels which empty 



themfelves into it, and thofe which are 

 conftantly fed by it, it has a Vein and two Arteries, which 

 sre proper to it, and by which its Subftance is chiefly nou- 

 filli'd. Thefe being wove all round hke a Garland, are 

 therefore calFd Coronarice. It has alfo many fmall 

 Branches of Nerves, which fpring from the eighth Pair, 

 and fend foi'th other fmall Branches to the Pericardiutn. 

 V. ,,_, . r Within the Heart there are two Fentri- 



c/es or Caverns, divided mto a rjght and 

 left, by a fiefhy Partition. The right of thefe Ventricles 

 is much the wideft, but not quite fo long as the left, nei- 

 ther is it of fo compad a Subftance, or of fo great Strength, 

 the Seplu??t, or Wall, being peculiar to the left. The 

 Keafcn of this difference feems to be, becaufe the right 

 Ventricle fends the Blood only into the Lungs by the Pul- 

 monary Artery, whereas the left detaches it into all Parts 

 of the Body. The infide of thefe Ventricles is very cu- 

 rioufiy made up, and interlin'd with feveral flefliy Pillars;, 

 jomewhat refembling the fmall Gotbick Columns. The 

 vJfe of which leems to be chiefly for the better Commu- 

 nication of the Blood and Chyle, being, in every Contrac- 

 tion, wrung thro' them as thro* a Sieve. 

 ^he Valve? of The large Veilels, which we have already 

 tke large Vef- obferv'd to retain to the Heart, and likewife 

 /ds, thofe by which it is conftantly emptied, have 



each 



