A Trutife ^/BODIES. Chap.26. 



into fmoke as before. And thus lie conceiveth the motion of the 

 heart to be made, taking the fubftance of it to be ( as I may 

 fay _) like unto limber leather , which upon the filling of it 

 with bloud and fteam , openeth and dilateth it felf : and 

 at the going ef h out , it fhrinketh together like a blad- 

 der. 



But I doubt, this explication will not go through the diffi- 

 cultv; for firft,both Galen andDodour Harvey do (hew, that 

 as foon as the bloud is come into the heart, it contra&cth it 

 fclf : which agreeth not with Monfieur dcs Cartes his fuppo- 

 fnion : for in his doSrine, there appearcth no caufcwkyit 

 fhould contract it felf when it is full : but contranwife 5 it fhould 

 go on dilating it felf, untill enough of the bloud which drep- 

 pcth inco the heart, were converted into (team, to force the 

 doorcs open ; that fo, it may gain an iflue thence, and a pafiagc 

 into the body. 



Next, Monfieur des Cartes fuppoieth that the fubftance of 

 the heart is like a bladder, which hath no motion of it fclfi 

 but openeth and fhuttech , according as what is within it 

 ftretcheth it out, or permhteth it to fluink and fall together 

 again. Whereas Doclour Harrey provcth that when it is full, 

 it compreffeth it felf by a quick and ftrong motion, to expell 

 that which is in it : and that when it is empty, it returned) to 

 its naturall dilatation, figure and fituation, by the ceafing of 

 that agents working, which caufed its motion. Whereby it 

 appeareth to beef fuch a fibrous fubftance,as hath a proper.mo- 

 tion of its own. 



Thirdly, I fee not how this motion can be proportionall : 

 for the heart muft needs open and be dilated > much farter 

 then,it can be fliut and ftirink together : there being no eaufe 

 put to fhut it and to bring it to its utmoft period of fhrinking, 

 other then the going out of the vapour, whereby it becometh 

 empty : which vapour not being forced by anything but by 

 its own inclination, it may peradvcncureatthe firft when there 

 is abundance of it, fwell and flretch the heart forcibly out; 

 b'-K after the firfr impulle and breach of fome part of it out of 

 thecavernc that enclofed it, there is nothing to drive out the 

 reft, which muft therefore fteam very leifurery out. 



Fourth- 



