 HOESA: Re Ti 
becaufe that contraétion throws the blood from the orifice motion. in the arteries. . Of this indeed we can form no 
of the veffel. But, if this fluid were fent to the extremities true eftimate, becaufe the motion is not progreflive, and the 
of the body by contra@tions of the arteries, the contracted blood does not flow, properly {peaking, but is puthed 
and relaxed tates of thefe tubes fhould alternate with the fuddenly by a gentle fhock, which cannot be fubjected to 
correfponding conditions of the ventricle, and confequertly, calculation.?’ ; 
each jet of arterial blood fhould take place when the ventricle. _ We take this opportunity of ftating, that the application 
is dilated, which is contrary to the fad. of the laws of the various branches of natural philofophy, . 
~ In the common deferiptions of the circulation we are in- and of the mathematical {ciences to phyfiology, in which the 
formed that the heart, by its contraction, propels the blood opinions juft animadverted on took their rife, docs not feem_ 
il i to us at all calculated to advance our knowledge of the 
b 
feen to rife at each pulfation, but to undergo hardly any tion is conftantly modified by. the Hang powers, and the. 
i ounded,. are them- 
traction of the left ventricle, general movement of the whole felves by no means fettled, . On this point, the fentiments 
mafs of arterial blood, and paflage of this blood into the of Senac, expreffed in the preface to his «* Traité de la Struc. 
inci: AGiones 
ame m ~ derive,” fays Bichat, «a very coincidé with our opinions. « P ns who, in {peaking 
exact idea of the circulation by exa ning the mefenteric, of their art, are onftantly recurring to. mechanics, an 
living animal, through the peritoneum. fprinkle their works with calculations, are only charlatans, 
each pulfation they appear to be raifed at once from their or men of heavy and. ignorant minds. endeavour to 
origin to their extremities. No correét notion of this fubject. deceive by afluming the ornaments of a {cience. foreign to . 
can be acquired by confidering the wave of blood as extend- medicine, and they incur, without fulpecting it, the con- 
ing at each contraétion through the arteries, and arriving’ tempt of true geometricians. What 
arrival at the capillary fyftem, during which it remains, for a_ ties, the tenacity of the blood, : § id 
certain number of eontraétions, in the arteries. According, which it poffefles. If each of thefe circumitances fhau 
to this mode of con ing the arterial part o circula-- be known, the great number of elements, which wo 
tion, which is the only true and ad le one, the windings into fuch a theory, would probably conduét us to yey! 
of thefe veffels cannot produ n. rd, tieable calculations. It would be the moft complex 
ological writers concerning the caufes of re-, fimple itate. When the Operations of nature are too com- 
tardation in the courfe of the blood, occafioned, rf, by its, plicated to be fubmitted to our calculations, experience. 18 
paffa m a narrower into a wider fpace, and by the our only remaining guide, we can only fupport our sso <8 . 
conical form of the arterial fyftem in general ; 2dly, by by indutions from numerous faéts. The notion that the 
friction againft the fides of the containing tubes; 3dly, by f{prings of the human frame 
the angles ; gthly, by the anaftomofes, &c. &c. All sats : Fak 
remarks would hold good if the arteries were em ty at the ficians, . Thefe fprings are unknown, multiplied, combined 5. 
moment of contraétion, becaufe the blood would Sa | 
have a progreffive motion; but, in the general and in-. ciate our ignorance,’” P..3 
itant When the 
. 
a 
5 
cacious. TI ftill return to the trivial, but illuitrating com- g pla ; 
parifon of the fyringe, Suppofe a tube fhould be adapted to fome red blood pafles into the general capillary 
ities ; if thistube fe ci the fing: 
aufes of retardation which might affe@ the ’s motion . tion experienced juft before; and are reflec 
if the arteries were empty, do produce no fuch effe& in the, original fituation. This is the fyftole, defcribed as #0 
ordinary flate of the veffels, that numerous judici i 
paffive ftate of the arterial 
thrown out of the ue 
the new quantity rouge 
fome pafles out at the oppofite a ri ‘ight P 
raction are 
. _Inthis view, the art 
| has been much ob y the” from it 
current notions concerning the velocity of the blood’s confequent on the paffage of the blood which ¢ 
