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ari, nothing is more in agreement With the laws of both, thau that two or more motions may SubSi Si Simultaneousty in otiobody or extense : and this is particularly the case in the animal bOdy, Where nature reigus in ali her science and art.' As in the lungs, for iuStanee, Whose arteries and vetus then especiallyconcur With the systole and diastole of the heari, when thel ungs themselves alternate their OKn motions in a disserent man-ner. LikeWise in the diaphragm, Whicli cooperates With both :also in every part of the thorax and abdomen, Where the motions of both the heari and lungs are constant aud persistent. Stillinore evidently in the pericardium, Which may aptly be compared With the dura mater; for it surrounds the heari much in
the Same manner as the dura mater Surrounds the brain. Thatthe pericardium is acted on in a generat manner Correspondingto the traction of the lungs, is evident Dom iis connection Withthe diaphragm, the mediastinum, the sternum, and the bronchial vesicles; hom iis insinuation between the iobes of the lungs; and Dom iis continuation Dorn the pleura : and stili iis arteries Leep time With the vibrations of the heart. Thus themotions of the lungs and heari in one and the Same Space, are
persectly harmoniolis, so that the members 1 reely live by their
ConeVrronee, because the fibres of the nervos are 1 illed by the motion of the One, and the arteries of the body by the motion of the other. Atid indoed for this reason the cardiae nerves arealWays transmitted through the peri cardium besore they go tothe paren chyma Of the heart. 61. Besore We close this section On the dura mater, I Will propose to the most experienced anatomisis of our age, a matterpossibiy Worthy of their further observation : namely, that thedura mater, Whicli in iiself is passive, and belongs equalty to the inferior aud superior regions Of the body, Seems to undergo pretiy nearly the fame changes in rogard to the direction of theblOOd-VeSSelS, RS We observe throughout the body, and particu
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also in tho dura mutor. The distribution os tho artorios throughthis membrane during infaticy, is Wolt shewn in a beauti fulfigure by Ruysch. Thes. Anat. V., tab. it., fg. 4.) Τhe distribution long after birili is represented in the figures of Ridley,
Vieussetis, Willis and others; in Whicli the suxion of the vesselsis seen to be of a Widely different character. Thus in the infantile membrane the vesseis are applied more closely to their Sinuses, and run in abundance Over the longitudinal sinus; butin the dura mater Os adulis, a large portiori of the vesseis is Obliterated, and changed into quasi-tendinous fibres, like thoductus arteriosus and umbilicat vesseis; that portion only re- maining Whicli agrees exactly With tho direction os both thomotion Os expansion and contraction. And this, to the end, that in the embryo the motion Of the brain may coincide Withtho motion of the heari, but in the child and the adult, Withthe motion of the lungs, and the motion Os the dura mater Withthat os both. And it Would be WOrthy of Observation, Whether tho coecat diverticula or foramina of the longitudinal sinus,
Whicli are closed in adulis, 3vere Open, and more numeroUS, iutho foetat state. XI. 62. In the present and last section, We propose to malle RDW Observations On the potui Os use, for Os right We measure
the animal system are concordant, and of What are not concordant, is immensoly conducive to the entire interesis of anatomy, medicine, and physiology : as We may inser more particularly from the faci, that the motions of the brain and lungs are themost universat and the predominant motions, by the coopera
over there re constitutes life in the animal, in the fame degree constitutos life in the sciences relating to the animal. But this subjoot Will bo bellor seen is We say a feW Words respecting it. 63. When we Obtain a linoWledge and distinci perceptiori of the universat anil natural motions in the animal body, We are
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vesseis in the body itsuis, in tho brain, niid in the confines be- tWeen the two, of Which Wo have hitherio boon treating. That We can comprehenit, for instance, Why the carotid artery in thohuman subjeci, arises as a branch and nos as a triank Dom thoarch of the noria: Why the internat carotid tWisis through thocranium in angular sexures and repented diametral gyres : Whyagain, after entering the cranium, it Winds abolit into similargyres; Why it expaniis into a ventricose bed Pari II., 11. 18), as do also the laterat sinuses; Why it puis oss the motive tunio of the arteries of the body, and puis on a plexi rm tunio instead; Why it subjecis itsulf to the dura mater, and after ards entirelyto the pia mater : With many other peculiarities, of Whicli in Our
preceding remartis We have, I thinli, Spolien as fully as the occasion Would admit. 64. By the fame knowledge We may also comprehend Whythe most generat nerves of the body, as the intercostat and parvagum, sent into the provinces of the body to go vern the natural motions, talio possession Os and enuelope the vesseis, as thecarotid arteries, and the jugular, Vertebral, and nZygOS Vein S, and their branches; for these nerves SO Order is, that Wheti theycomo into the Lingdom of the heari, they stili pass under thecontroi of the brain; and cause nil the special and particularmotions of the botly to terminate in the universat motion of thobrain, and the common motion of the lungs, just as they begin om them. For it is indoeil highly interesting to observe thattho motions of the living body constitute an entire Series, therebeing primary, intermediate, and ultimate motions; and thattho intermediate motions, Whicli are also hept in a certain series by their proper motions Whicli are more universat than them solves, subsist and flourish under the auspices of the most uni versat motions. These, and Severat Other things, Will novor botraced to their causes, I mean, they Wili never be laid opon to the rational sight, or to the minii, uniess We sirst know thetimes, modes and nature of the motions. 65. From a distinet perception of the ab OVe motions, Womay also perceive Why the blood-vesseis of the bruin and dura mater, and the blood-vesseis of the hody, undergo Such remarkable changes as soon as the insani or chicli is excluded into thoatmosphere, and begitis to draW the neW breath; Why it salutos
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UnleSS We explored the nature of the motions Whicli are theossicients here.
66. Mucii tess Without a previous knowledge and distinctperception Os these motions, can we understand hoW the brain, and the human brain particularly, is enabled to be the moverand dispenser of iis biood : how it has the poKer of not admit- ting more than iis state requires; and this, With so notable adisserenoe in man and in brutes. For by these means alone Canthe brain bu len to itself, and to the analysis of iis reasOns: by these alone can it so govern ali things, that unanimity may stillreigii Over the discords of the bony, as it does When the brainsears no invasion Dom the blood of the bo , Whicli cannot bursi in Without iuvitation, because the animations of the bratus and lungs are coincident. And ns the brain has the power of acting upon iis fibres and vesself, it also has the poWer of actingupon the muscies, Whicli depend upon the fibres: Where re Without a concord existed botmeen the motions of the brain and lungs, the brain could exercise no jurisdiction, hecause it could
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motion of the brain and nervous fibres; sor then the contagionwould diffuse itself upWariis and doWnWardS equat ly. 68. These utilities then me promise to anatomicat, phyStological, and pathological science, Dom a knowledge and distinet perception of the coincidence of the motions of the brain undi ungs; hom Whicli, after We have expOunded them in their universat reiptions, it is easy to descend to particulars.
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69. WHEN designing to treat of the brain, I Was sor a long time indoubi hom What potnt to commence ; Whether from the dura mater, whicli is the first part that comes in view On Opening the head, orwhether froin the arteries of the brain, considering that in the former Pari Ι had treated of the arteries of the body. But Whereuer I turned, I could not help recognising in the brain a more than Gordian knot, and nil things SO concatenated, that one Was. to be Sought in the other, thelast and the middie in the sirst, and vice versu ; so that unless I v ould mahe up my mind to uuravel the entire brain, it Would be in vain toattempt to Unravel a pari: proving that a special treatise dedicated toone part of it alone, Mould Serve only to deser the reader's hopes, and toreser him Onwards to the nexi links in the chain. Stili, to evolve theentire brain in the method Hready beguit, I found to be a Work of greater extent than could be comprised Within the limits of a single Ρart. What then was to be done i I must begin som0Where ; and theresere Ι resolved to begin stom that whicli is specificatly called the corticaland cineritious substance. The reason is, that this Substance, proxi- mately, is the principat efficient cause of the operations not only of thebrain, but also of the body ; for it is this substance that animates audspirates, and excites the whole of the animal machine to motions and modes : that eliciis the purest spirit of the blood froin the arteries, and transfuses it into the fibres of the medullary substance, and from thetice into the fibres of the nerves : or, finalty, this it is that is siluated in themiddie, betWeen the principat fluids of the animaled System, namely, the
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blood and the fluent spirit; and consequently in the centre os ali thes uitis, or in tho srsi and last term os all. Wheres ore, in ordor that Imight contemplate the posterior Sphere frona iis frst principie, and the sphere of consequents from iis highest antecedent, I Was under the necessity of beginning, or taking my principies, from this substance. This SubStanee Once explored, it becomes ea sy to turn to Whatever poliat Iplease, either to the sursaces of the brain, namely, iis arteries, SinuSeSand membranes ; or to iis inner substance and members ; or to the inserior sphere, nainely, the body itself 0. Ιt is to be notod, that in the present Pari I have proposed toobserve the fame method as heretos ore; namely, bes ore entering Uponthe subject matter of the Pari, to premise the observations and eXperi- ence of the most learned onquirers, by way of Dundation; theri fromthese to form a generat induction, the clauses of whicli I shali asterWard sconsider in minute delail. I could not devise any other method that appeared to me more a hin to the peculiar operations of the minit itself, and beller adapted for unsolding phenomena, and unlocking the nreanaos nature by the aid of experience, and the force of rational philosophy. Here then follos Our factS. I. LEEUWΕΝΗΟΕK. First os ali I underi Oh to examine those palis of the brain of an Indian hen, Whicli are commonly termed thecortical Substances. These paris . . . are composed of a Very pellucid, c Stalline, and . . . oily matter, of so limpid and pellucid a character, that it ought rather to be called the vitreous, than the cortical substance of the brain. When I attempted to separate this matter into iis least
red Color. . . . BeSides the smali globules We have mentioned, there Were certain larger Ones, fix of Whicli I rectioned would be equat in sige toone globule of OUr blOOd. . . . Moreover, there Were certain Clear and irregular globules dispersed about through this substanee, sonae of whichwere equat in sige to a globule of Our blood, While others Were larger. Through this pellucid matter and these globules again most minute blood-VeSSelS Were Scattered in great numbers, . . . many of them being indeed
so minute, that to judge froin the eye, is one of the constituent particles of the plano-ovat globules that redden tho blood of fowls and other bird sis one of the particles existing in the round corpuscule were dividedinto fifty paris, even such paris Would stili not be sinati enough to
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Other in layers three or mur deep, Without any other matter interposed
belWeen them . . . . BeSides the above-mentioned minute vesseis in the
into more than a thousand paris, could permeate them . . . .
72. Coming to the medullary paris of the brain, I there mei Mithcertain irregular globules of disserent siges, some of them equat to One Obule of our blood, sume of them larger, and Whicli, to judge stom theeye, consisted sor the most part of a thin, pellucid and olly substance. These globules are found in the medullary part of the brain sparticularly in the place Where the spinal marrow commences), and in Such abund- ance that they seem to constitute the greater part of the brain. Thisvast multitude os pellucid globules is What causes the white color os
the medullary substance . . . . These irregular globules Were SO closelyunited together, that when I saw any Which were Sinali Or Single, and attempted to Separate them, sonae of them underwent an eXtensioniWice as great as their tength seemed to admit, and appeared to me tobe connected by threads in the form os a net. . . . The opinion I had formed, that many of these irregular globules Were Surrounded by VeSSeis, Was confirmed When I saW that many of the vesseis bes rementionedWere transparent in the middie, and SomeWhat opake at the fides; and stili more When I sound that on the globules bursting, a number of sine
73. In the course of my inquiries I took the head os a Sheep, andon examining iis brain, I found in like maniter in the cortical paris avast number of extremely minute blood-vesseis; and I recogniged that the substance that gives the blood iis red color Was contained in them, Whicli vesseis there re also communicate a brownisti color to the cortical paris. This incomprehensibie multitude os exquisitely sine blood-vesseis I frequently beheld With my Ourn eyes, . . . and I SRW QmOStevery Vesset again Splitting into tesser branches. . . . Aud I imagined tomyself that the globules . . . Whicli constitute a sigili part of One perseet bl00d globule, meeting With vesseis so narrow that they cannot pass through them, are under the necessity of being dividen into tesserparis, and that the above narrow VeSSeis are deStitute os color. . . .
Νevertheless I am os opinion that these sinali particles of blood arealways flexibie, just as those blood globules that have come to persect
lary paris of the brain. . . . In the medullary paris running to ardes thebeginning of the spinal marrow, I thought somelimes that I sam veryclearly . . . that the large tranSlucid . . . and Oily globules Were in a
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74. During my investigation of the cortical paris of the brain os the ox, I have osten thought that I could see and observe that thevitreous and highly pellucid matter that constitutes the principat partof the cortical substance, consists of nothing but very sine lines orvesseis, ali joined together in the closest maniter . . . . Ι also investigated the cortical paris, Or cortex, of the brain in sparrows, immediately after Ι had killed them, and here I observed sinali blood-vesseis of ali hiud s. . . as clearly and distinctly as Ι had observest them in the bratris of the ox and sheep; and ali the other microscopic paris of the sparroW'sbrain Were of no less sige than they are in the OX. . . . Anil When I Re- curately examine the vitreous or cortical substance of the brain, it seem sto me to consist of nothing else than an inconceivable multitude of the
represent a vitreous substance under the microscope; and this, evenmore clearly in the sinati brain of the sparrow than in the large brain of
the OX. . . . The minute veSSeis that in pari constitute the vitreous
Substance, I find are so smali, that a largisti gratu of sand would have tobe divideli into many millions os paris besore it could pass through them. . . . The remaining paris of the white brain of the sparrow did not dissor froni the white paris of the brain of the ox, sheep, and Indian seWl, . . . eXcept that the pellucid Gily globules that were in a maniter bes et With vesseis, Were by no means so large in the OX. Arcana Naturne Delecta, in Oper., tom. i., p. 30-39 ; Epist. de Structursi Cerebri, &c.)75. When Ι examined . . . the structure of the pig's brain, Ι hadno disticulty in determining that there must be a connection belween theblood-vesseis and the particles of the brain; in order that these particles may be supported, and their vitali ty hept up, by a never-failing Supplyof blood . . . . The author has a figure si) representing a minute portion os a pig's brain; Where We See that severat arteries run doWn fromthe pia mater, and are united to each Other by threatis, Whicli Leeuwen-hoeli calis the fibriis of tho brain, and whicli, tili this time, had esca peditis notice; these arteries run perpendicularly, and contain but litile redbl00d. J ... Ι rechon that theso fibriis of the brain are fuit four timesas large as the fleshy fibriis of the ox. I placed under the microscope a Very smali portion of brain, in Whicli there appeared an incredibie multitude of blood-vesseis, cui osy both transversely and directly asSheWn in the plate . . . . Through ali these blood-vessel S, Whicli are eX-hibited in tab. ix. , except those Whicli are invisibie, and do Π0t Occupymore Space than the sursace of a largish grain os sand, there is no doubt
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does any one of them potir out the blood through iis extremisy, as SomeW0uid feign. V istota Physiolostem epist. XXXiv; in Oper., tom. iV, p. 330-336 ; see also to p. 339.)76. ΜΑLPIG111. It is quite obvious to the senses, that the cortical Substance of the brain is not the produci of coagulated blood, butis a Lind of peculiar parenchynia, fuit os minute poreS and paSSages, that Serve as a sieve by Whicli a portion os coagulabie serum is sistedfrom the blood . . . . In the bratiis of red blooded and persect animais, I have found that the overspread cortex is an assemblage and congerieSOs most minute glaniis, Whicli in the gyros and long-drawn intestinula of the brain, where the white roseis of the nerves terminate, Or rather, is yOH PleaSe, originate,) are stted together in Such a manner, as by their gr0uping to produce the exterior sursace of the brain. They are of an Oval figure, but compressed ali round by the adjacent glands, Whicli createS certain Obtuse angies, and a great number of pretiy eques intermediate Spaces. The Outer portion of these glands is covered by the pia mater and iis biood-vesself, whicli penetrate deeply into their substance ; the inner portion puis sortii a White nervolis fibre, as it Werea peculiar vesset, as the lucidity and whiteness of the glands permit usto Observe; the white medullary substance of the brain being in factproduced by the connection and fasciculation os many of these vesselsor fibres. And is the nature of the cortex may be explained by a familiar example, no beller One can Oecur than the Structure of the pome-
granate, in the symmetrical grouping of the granules of Whicli, We arepresented With an image of the gland s of the brain, Which by theirgrouping produce the cortex; While the sibi es, issuing froni each granule, and conveyed through the membranes, exhibit a rude image of the medulla of the brain. And I recollect having Seen Some youngilates, Which, as they hung on both sides of the stem, resembled theglands of the brain, While the vesseis or fibrous structures by Whichthey hung, ultimately formed a fasciole, and so were analogous to the
corpus callosum and eorpus medullare.
But these cerebrat glanus are seen with difficulty in the raW brain, even though it be the large brain os perseet animais; because they are lacerat ed by tearing aWay the pia mater, and their conterminous limits are not eastly distinguished by reason os their lucidity, Dor the spaces
seen when the brain is bolled, during whicli process they become thickened, and the intermediate spaces are better desined, particularly in thesides of the convolutions; and they become stili more evident by peelingoss the pia mater, particularly is they are examined While yet Warm. A