Sjtiee the Heart is no 'more^^^^^ Mufcle' of ai pacAi- 
jliar Frame, it is certain the force , applied to cauft it 
Contradion, muft te oi' a like nature with tha* of the 
: 9ther Mufcles in an Animal Body. ^ It is agreed by all, 
-the contraffion of tl4e&^^% 
on b^drttiiti^ of the whichj compofe 
^their BeHy; ■ ' ' ^■-i; ^ '- • y^ 
lihis part, whkh alone- fufFers alteration of its Fi» 
gure in Mufcular Aftion,^. is compofed of a multitude 
of Prifmatie^: P^faHel Fibres, with innumerable tendi- 
nous Threads, paffing from one to anotherf 'ahd bind- 
ing -em to^neri Let us then confider thefe Fibres as fo 
many parallel Ropes, with one weight fufpended at the 
bottom of them. It is plain then t^ie diftance between 
the upper and lower extreme can only be leflened, and 
the wetgfa't'-ndra vvn up in o n e of —thefe-i^ltowiflg 
ways. If fome String or Body without the Ropes 
draw thm^^^i^\^^ between 
them, aqd^^ft^r^the^ani^oi^a^^^^ to 
fgqdde^ 'or^ laM^ ,'c6rnprefB 
arid force 1:}le^t<i afipr6k6h^^^ti^6iA&r, ^aj^ 'ho ^ cither 
way than thefe c^tJ^ t)e^\lpE»Mi\5^ 
the weight fo placed. 
By applying the^ Priqcipl^p^ tj^ prpmifed , and con- 
^fi4erjng well ^Jik^v&^^ it; will without 
.mi^^h d^iflicd appcaj /wj^cn^p.j^^ is moft 
likely to pr9cee:d.. .^ Jf w^^pjf^i^' a,pia^^ fcrutiny into 
the B^eaft, a^d exaipirret^f^P^W we (hair not 
iind any Threads, Strings, or ol her exteriour power 
•^f|(|)able of deducing or drawi^.g afu^der the. Fibres of 
the Heart. There are indeed'^'withiri it divers Tendi- 
nous Threads ; ariflng frp^ . jt^^, i^qfting Membrane, 
whict^jermina^e inits inuicft' fuD(|aiip^ iaterfedirig the 
Carneous Fibres, and binding th j:n together. * But Jt 
cannot be fappofed thefe ferre to contraft the Heart, 
is no force bwyoai to draw them. Ag^in, if 
we 
