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the ligatures, not only because it admitted into iis Own proper cavlty the esservescing blood expelled from the ventricies of the heari, butalso be ause below the ligatures it Was provided Mith nervolas fibres, through whieli it received the animal spirit as the principat causeos iis dilatation and contraction; for during the soregoing experimentSwe Deed aud separated the artery froin the nerves and ali theneighbouring paris as sar as Was possibie to be done. Tahing allthese facts into account, I must continue to be Os opinion, that thedilatation of the arteries deperius solely on the impulse and expansive
force of the blood . . . . It may be Weli to ObServe, . . . that in thesrst experiment the artery always pulsated a litile more Debly belowthe iube than above it, hoWever large the cavlty of the lalter might be . . . . Furthermore, long eXperience has taught iis, that thereare many persons in Whom although a susticient quantity of blood may be contained in their vesseis, and the impulsive motion of thelieari may be sussiciently strong) no pulse can be seit at the wrisisor Other paris of the extremities, when the extrinsic principies of theoxpansive motion Of the blood have beeome essete and inactive. . . . In the srst place We tied a dog's crural artery With two ligaturos, and dividedit across midWay between them, and we then lied the crural vein. When this Was done, the artery sensibiy collapsed below the inserior ligature, While on the other hand the vein sWelled up in the correspond-ing siluation. Yet every one must See that the heari's impulse Wasintercept0d, While the bl od was moving in the above vesseis below theligatures. Frona whicli it is susticiently olear, that the blood has in ita certain pOWer of eXpansive motion, Which by no means depentis onthe heari's impulse, and that by this power, With SOme assistance derived se in the motion of the muscies of the legs and seet, it passed froni the crural artery into the crural Vein during the performarice of the foregoing experiment. In the Seconii place, a Strong dog Was saS- tened to the table, iis abdomen laid open, aud both iis illac arteriestied. The sternum being then separated froni the diaphragin andribs, and laid bach toWards the head, We as caresully as possibie tied the ascending trunk of the aorta, and the other vesseis of the hearinear iis base, together With the pericardium. Τhe motion os the
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beari thus entirely intercepted, we made a stight incision into the de- Sceniling trunk of the a orta, When the blood spiriod froni iis cavlty ith great force, and as it were in distinet jets ; Which Would by nomeans have been the case had there not been an expansive force in theblood. Neurographia Universalis, lib. i., cap. iV., pp. 22-27 ; sOL,
l23. ΜΑLPIGHI. . . . In the silli orna, directly from the politis orStigmata that are visibie externalty in the whole of the rings but thesecond and third, there arise certain re markable ramifications Of ves-self,' Whicli run to ali paris of the body. These ramifications are Without any apparent trunk, but in each orifice or stigma are sitied ten considerable branches, and somelimes more, Whicli terminate in one commonopening or hiatus, so that this insect has eighteen plexuses of branches of this Lind. . . . From this hiatus, or stiori trunti as it may be called, two circles for tubes arise, Whicli run respectively to the pleXuses situ-ated above and below, thereby creating a mutuat anastomosis from thehead to the other extremity of the body. . . . These Vesseis ramisy like arteries, for the further they proceed froin the trunk, the siler they b0- come, and in Various paris they give osy numbers of tWigs, whichmostly form reticular plexuSes, Such as may be observed in the leaves of trees ; and this is more particularly the case belWeen the muscies and the shin, Where the luxuriance of these vesseis is so great, and their inter estvings are so Wondei sui, that it is impossibie to have a more
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evident to him, that the bl ood-vesseis Observabie in this creature, and Which we are Wont to distinguisti into arteries and Veius, are One and the Sume claSS Os Vesseis . . . . But in the place Where he thus vlewed the circulation, the arteries were not Wider than to allow single particles
of blood to pass through them Without impediment. Aud even these particles, Whicli appeared for the most pari globulari occaSionalty assumed a tapering figure to fuit the tenuity of an artery; althoughthey are so minute that a hundred thousand myriad of them are note luat in bulli to a large grain os sand; Wheuce We may eaSily conjecture how minute must be the vesseis in Whicli the circulation is carriedon. Again, in a frog of larger sige, he saw that the blood running in the great artery, and derived into a tWig or litile artery, WaS SOmetimeS
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gi Veri oss; the cause of whicli circumstance he considers to be, that thebl00d had met with sonio stight impediment, or that Some nerVe OrmuScle adjacent to these litile vesseis, so pressed iapon them RS to ObStruct the current. For aster a stiori time, that is, When the impediment, RS he preSumes, Was removed, the blood again resumed iis Ordinary direction and rapidity. In certain sua ali sishes a litile longerthan the tadpote first mentioned, and dotted on the si in with blackSpOis some of Whicli resembled litile stars, he observed, to his great gratification, the circulation periodum of the blood not in one onlybiit in severat disserent places . For on erecti fide of the ossicles Ortitile bones that give rigidity to the fius, every artery made a curVe Orinflexion, and thus constituted the beginning of a vein ; and the agitation of the blood that flowed or was protruded froin the large arterytoWards the extremity of the tali, and that asterWards returned throughnumerous litile vetus tOWariis the great Vein, Was sO considerable, ascati scarcely be belleved. Besides Whicli, in the presence of many spectators, he submitted a variety of Smali fishes to the microscope ;and with such success, that those Who Were With him, Saw most distinctly, With the greatest admiration and rivetted attention, the circulationos the blood in severat vesseis at One and the Same time. ΝOW Domthe faci, that distinet currents of blood may be seen in the talis offuch minute sisti, he justly concludes, that in the human body the number of these currenis must be incredibiy great; and that it is nowonder that a flow of bl00d should take place When we are prichedra illi a noeille or Other sinali instrument; for si om his oWn Observations he is convinced, that in an area no larger thau that Os a finger-nail, there are more than a thousand distinet currenis Or circulis. In thetatis or sits of larger fishes he olearly SaW a great number of blood-Vesseis, admitting only Single particleS Of blOOd. . . . More than Once
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extremity of the sn, he could discern an elevation Or rising in themost minute blood-vesseis, corresponding to the moment of Pach resti impulse that the blood received frona the heart. In One Species of eel, between the severat ossicles that forni the extremity of the caudat sit, he saw the blood circulating in vesseis through WhichtWO Or more Os iis particles could travel abreast, and many of the arteries also were there inflected, and constituted vetiis. He observed the circulation . . . in the filis or feet of fishes, in the wings of bais, in the watiles of cocks, and in the ears of rabbiis . . . . When hedissected the artery or velit of any animal, and the vesset Was emptiedos blood, he found it pure and white on the inside, as is it hadnever contained blood at ali; in stiori, in no ise dyed or discolored. Heiace he legitimately argues, that the vesseis are formed in sucha manner, that they keep even their fine j uices ; although this rule is not to be extended to the minutest ramifications. When ho dissected ossilie exquisitely thin, inner membrane of an artery, and submitted it tothe microscope, he perceived, to his admiration, that it consisted os an incredibie number of wondei fully minute paris running one throughthe other, and ali connected together in the maniter of a network; and When he separaten and examined the other part of the tunic that thes ornier had c vered, he found iis fibres stretching round the artery, Sothat this tunic, being exceddingly tough, Was adapted more to the expansion or contraction than to the elongation Of the nrt ry. . . . Some-
times he saW a clot of blood concreted in a vesset and bloching it up, and then gradually the cloi Was perforated by the constant strOke Orimpulse of the advaneing current, uniit at last it transmitted a thread- like stream through the middie of it, and in faet aeted as a tube inserted into the vesset.'' langet, Bibliotheca Anatomica, tom. i. , P.
subjecis in peculiar vesseis termed arteries and Veins, Or else in certain receptaeles of an intermediate character, Such as the Venous Sinuses of the heari, liver, and dura mater, the auricles and ventricies of thelieari, the Spongy Substance Or celis in the male and female genital organs, and perhaps also in the Spleen. The arterieS are membranous canais,
conoid, oblique, inflected and branching, Sinooth on the inside, and destitute of valves, excepi in the heart. Their branches vary in their modeos origin. Generalty they arise at acute angies toWards the apex of thecone; seidoni at right an es like the intercosials . . . . They conSiSt Offive costis, the most external of Whicli is thin and nervous On iis exterior sursaee, but on the interior consists of a very thieli Detwork of ar-
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teriai vesseis, derived froni the coronary and other arteries, and inter-WOven with vetris. This coat it is whicli attaches the artery to thel rOXimate paris. The seconii is a thin and cellular coat, very dilatablewhen iis celis are inflatod ; and whicli, by potiring sortii an Oily, falty and lubricating fluid iapon the muscular fibres, admirably sis them topersorin their incessant contractions and expansions. The third coat is glandular, and probably is no more than a layer of the Second coat,
comprising principalty salty sollicles that run to the solarili coat. This
urth coat is muscular, and is made up of highly elastic annular fibres, many rOWs thicli, and divisibie into a number of lamellae. The fifth and last coat, Whicli lines the internat sursace of the artery, is thin and membranouS, and appears to consist os longitudinal fibres, whicli are contractile, like those of the fourth coat. While life and hostilli continiae, this Whole Vesset moves and pulsates. But iis extremitiesare very Variousty formed, So that in one part of the body iis fabrio is sar disserent froin What it is in another ; disserent, sor instance, in respect of the fige of the aperture With Whicli it originates froni thetrunk ; in respect of the thichness of iis costis, of the number of iis branches, of the disserent angies at Whicli these are given osy, of their inflections, inter eaving, diviSion, yc. These arteriai extremities terminate dither in the beginnings of the litile vetris by a continuous canal, Without any intermediate parenchyma or caVernous Structure ; Or elSein crypis, or follicles, Or in the large or Smali cavities in various paris of the body ; or in excretory Ve8SelS ; or in particular SinuSes, as those of the penis, clitoris, and Spleen ; Or directly in Secretory VeSSelS ; or perhaps, lastly, in a glandular pulp. The Veins have almost the Same figure auddistribution as the arteries, but they are of larger capacity and perhapsare more numerous ; besides Whicli nil their membraues are muchthinner and more inert. They have valves, Whicli are generalty single at the insertiori os the branches into the larger triantis, being oblong, and shaped like a glove-finger; but whicli are mostly combined in patrs in the strati trutilis of the larger vetiis that are more remote fro in thelieari and convey the bl od perpendicularly upWarils ; and such is the
Structure and connection Of these valves Within the vesseis, that theyadmit the blood froin the sinalter branches into the larger, but preVentit S regress When the heari contracis, and sustain iis column. The vetiis in the living animal have not naturalty any pulSation, nor nnythrobbing motion like the arteries. Their extremities are VariOUS, RS We observed to be the case in the arteries; some of their radicles commetice frona the litile bibulous mouilis of the cuticle ; Some, froin the absorbent ducis placed ali over the body, in the internat, hollowmembranes that forin crypis, follicles, or large or Smali cavities ;
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others arise immediately froin the extremittes Os arteries, or else Domcertain Singular analogous channeis Or Sinuses, as in the peniS, clitoris,
and Spleen ; or lastly, perhaps frona a glandular pulp. The whole of the arteries dispersed throughout the body are connected by continuityos channei and substance with the trunk of the norta, Where it arises froni the lest fide of the heart. But tho se arteries that enter into the structure of the lungs, proceed aster a similar maniter from the pulmonary artery, Whicli arises fi Om the right Side of the heart. . . . Theorifices of the aorta and pulmonary artery at the heari a re os equaldimensions. All the vetiis dispersed throughout the body have thesame relation to the Vena cava af the arteries to the aorta; butthe cava s Orms a large sinus couered With a membrane like that ofan artery, and thereby terminates in the cavlty of the right auricle and partly in that of the right ventricie. But those velns that enter into the structure of the lungs, open by sour great branches into a Sinus similar to the former, Whicli is prolonged into the lest auriclennii Ventriete. . . . Both the arteries anil vetiis are largost at the heari,froin thenco they gradually diministi in diameter, and almost constantly accompany each other closely in their distribution, through nil the severat regions of the body. The area of the orifice leading froni the Vena cava Or auricle into the right ventriete, is to the area of the pulmonary artery as 47 to li4. Institutiones Mediere, n. 13l-135.) Ιs an artery be laid bare, and lied With a ligature, it swelis and beats be- tWeen the ligature and the heari; but becomes saccid belween the ligature and the extremittes ; and at the fame time the neighboring arteries, whicli are stili pervious, are found to pulsate With unWonted strength. And is an incision bo made belween the heari and the ligature, the artery continues to seud out a sWisi and starting j et of blood, tili theanimal presently dies ; but is the artery be even cut in two belween theligature and the extremities, not more than a se drops Will escape. But sor this experiment the artery should be single, and should notcommunicate by anastomosis With any large neighboring artery in the part beyond the ligature. Ibid. , n. 141.) Is a large velit be in likemaniter laid bare and lied, it swelis belW00n the extremities and theligature Without any pulsation, but appears empty and saccid belWeenthe ligature and the lidari; and is an incision be made in the formersituation, the bl od continues potiring out illi the animal soon eithersiainis or dies ; but is in the lalter, litile or no blood sollows ; nor is it
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it flareibly compresses the fame, and contracts of iis OWn a cord RS SOOHas the finger is Withdrawn. In a living animal the artery appears fuit, but it is soland sinali and nearly empty in a dead human body, eVenWhere no blood has been lost previ0usty to dissolution. The arteries resist inflation, sordibly repelling the air that is driven in ; and in contracting, they rest at the potnt of the least diameter. . . . There iS nota percepti ble pari, hoWever smali, in the compass of the body, but hasiis litile artery; as we are taught by the bleeding that follows smallW0uniis, by the phenomena displayed by the microscope, and by the process of injection; and this remark applies even to the very middie of the bones, where We finit both membranes, VeSSelS, and humorS.Νevertheless, ali these arteries are Omeis froin the trunk of the norta. V Ibid., n. 2l3, 2 ld.)127. Variolis modes have been adopted sor calculating the quantityos blood in a living animal. Some fix the quantity in man at 25 lbs., Others at 10, Others at S. It is salit that in a sheep the meight of theblood, compared With that of the body, is as 2 to 22, and in a lambas 1 to 22. Large quantities of blood have osten been lost in hemorrhages from the nose. In Oue caSe 48 tbs. Were tost in three days ; in another case, 75 lbs. in twelve days : See the Acta L,δien/ia. The pulse varies With ait the disserent morbid affections os both body and mitid; thus it may be strong or Meah ; or intermittent, for instance, beatingrapidly twice, and pausing bellare the third beat; or it may be palpitating. The ancients distinguished pulses into severat varieties, suchas undulatory, Vermicular, formienting, bounding, mouSe-like, dolabie, uiaequalty eques, irregularly hurried, Serrated, yc. Some doubi theexistence of What the ancients called revulsion, by Whicli they meant the abstraction of the blood from an inflamen viscus, by venefection; and of what they called derivation, by Whicli they meant the determination of the stream in a neW direction.
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128. ΤΠΕ blood, in ordor to flow determinat oly to iis endsand uses, floWA Williin tunicased vesself, through Whicli thecirculation is carried on; a circulation, namely, Dom the lest ventricle of the heari, through the arteries, into the VeinS, and Dom the vetiis into the right ventricle; Whetice it returns through tho lungs into tho lest auricle of the heart. As tho blood itsuis is of a three ld Origin, degree, naturo. CompOSition, and Dame, So is also the tunic os iis vesseis; in ordor that both the continent and the content may aci asone common cause of determination. The membranes, Whichare Severat in number, correspond to the severat degrees Ofblood; one being prior to the Other, more uni VerSal, more perfeci, and more simple. Ali these membranes fallen collectively, and connected by mutuat superposition, in close and conveythe red blood: membranes foWer in number and more Simpleinclose and convey the purer blood : and One simple membrane inclosos and conveys the spirituous fluid. COHSequently, in the vesseis, equalty as in the blood and membranes, there are three degrees of composition to be talion into consideration, ali Os Which should be distinctly perceived. The vesseis of the first degree are those commonly called blOOd vesseis ; the vesseis of the second degree are the eXsangui ous Ve88eis; and the vesseis of the third degreo are the fibres of the nervos. In conformity With these various degrees Of
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Ve88eis, the circulation itseli is subtriplicate; namely, sirst, nle8S universat circulation, Whicli is that of the red blood; Secondi , n more universat circulation, Whicli is that of the purer blood; and third ly, a most universat circulation, Whichis that of the spirituous fluid. Whilo the rod blood is passing Dom vesseis Os iis OKn Order into vesseis of another ordor, it bucomes dividen tuto the purer blood, or into blood of the second ordor; the Saline,
degrees similar to those by Whicli it had beo me dividod. Suchis the mannor in Whicli it performs iis universat circle, netther the buginning nor the end of whicli is determinabie, but bymeans of Whicli there is nothing that tho blood, in iis omn