Page:Cyclopaedia, Chambers - Volume 1.djvu/273

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\ entricle, or Rma, which is in the Medulla oblongata, hi likewife two Apertures i the one the Orifice of the Infun- dibuium, or Tunnel, which is a Canal reaching to the Glandula Pitnitaria : The other is a Duel, whercbv the third Ventricle communicates with the fourth in the' Me- dulla oblongata, under the Cerebellum. That fourth Ven- tricle is in the form of a Quill, whence it is fometimes call'd Calamus.

In the Lateral Ventricles are found the 'Plexus Cboroidcs, which is an Affemblage of minute Veins and Arteries • and four Eminences, the firft the Corpora Striata, the' others the Tbalami Nervorum Opticorum.

At the Entrance of the Canal reaching from the third Ventricle to the fourth, is fituatcd the 'Pineal Gland ; fo call'd from the Figure of a Pine-Apple, which it refembles : This Gland, 'Des Cartes fuppofes to be the Seat of the Soul. Behind the Pineal Glands are four Eminences ; two upper and^ greater, call'd Nates ; and two fmaller and lower, call'd Teftes. See Medulla Oblongata, to which all thefe Parts properly belong ; fee alfo each Part under its pro- per Head, Nates, Testes, Thalami, Pineal, Plexus, Calamus, £5?c.

The Veffels of the Brain, are Nerves, Arteries, and Veins. By turning up the Brain, the Origin or Bafe of the Nerves proceeding from it, are diftinctly feen : Thefe are in Number ten Pair, viz. the OtfaSory, Optic, Mo- vers of the Eyes, Pathetic ; the fifth Pair, and fixth Pair, call'd alfo the Gufiatories, the Auditory Nerves, Par va- gum, and the ninth and tenth Pair.

The Blood- Veffels of the Srain, are the two Internal, Carotid, and the Vertebral Arteries. The firit piercing the 1)ura Mater, communicate with the Cervicals; andproceed- ing thence, fend a Branch to the Plexus Cboroidcs ; till arri- ving at the Via Mater, and making feveral Turns and Circumvolutions thereon, they terminate, at lair, in the little Glands that conflitute the Cortex. The Vertebral Arteries paffing the Dura Mater, go along the under fide of the Medulla oblongata ; till giving Blanches to the Spi- nal Arteries, they join in one Branch call'd the Cervical Artery, which communicates with the Carotides by two Branches, as before. The Veins of the Srain don't run along by the Sides of the Arteries, as in other Parts of the Body, but rife from their Extremities in the Cortex ; whence they difcharge themfelves into the Sinus of the Dma Mater. See Carotid, Cervical, &c.

For the great Bulk of the Srain, this Reafon may be aflign'd; viz. that on account of the exceeding Subtility and Finenefs of the Animal Spirits, and the Slownefs in which their Secretion mull be effected ; together with the great Quantity of 'em requir'd in difcharging the animal Functions 5 there mud of neceffity be an'infinite Number of Glands to feparate and prepare 'em. From the fame Principle, we fee why the Srain is much bigger in Men than in other Animals ; and in other Animals, why, ceteris farihls, it is biggeft in thofe which difcover the greater! fhare of Sagacity, v. g. in Monkeys, S?c. A confiderable Stock of Animal Spirits being to be cmploy'd in the Affairs of Cogitation, Memory, (gc. Accordingly, Anatdmifts ob- ferve, that in Fools the Srain is fmaller (ceteris paribus) than in Men of Senfe j This, fome may account for, by fuppofing it the Caufe of the Folly ; a fufticient Stock of Spirits being wanting to reafon, £$c. flrongly : And others from the Oeconomy of Nature, which proportion'd the Stock of Spirits to the Expence that would be requir'd.

From theTexture, Difpofition, and Tone of the fibres of the Srain, Philofophcrs ordinarily account for the Phamome- naof ScnfatiouanA Imagination 5 which fee. Dr. Aftruc goes further, and from the Analogy between the Fibres of the Srain, and thofe of Mufical Inftruments, folves the Phe- nomena of Judgment and Reafoning, and the Defects and Perfections of both. He lays it down as an Axiom, that every fimple Idea is produe'd by the Ofcillation of one de- tetminate Fibte ; and every compound Idea from cotempo- rary Vibrations of feveral Fibres : That the greater or lefs degree of Evidence follows the greater or lefs Force wherewith the Fibre ofcillates. He hence proceeds to Lhew, that the Affirmation or Negation of any Propofition, confills in the equal or unequal Number of Vibrations, which the Moving Fibres, reprefenting the two Parts of the Propofition, via. the Subject, make in the fame Time : i. e. If the Vibrations of the Fibte that gives the Idea of the Subject, and thofe of the Fibre which gives the Idea of the Attribute of Propofition, be Ifochronal, or make an equal Number of Vibrations in the fame Time, we are de- tcrmin'd to the Affirmation of the Propofition; if Etero- cronical, or their Vibrations be unequal, the Soul will be determin'd to a Kegation, ?$c. Hence refult Confonanr, Diffonant, Hatmonkal Fibres, £Jfc. The Evidence and Certainty of a Judgment, Affirmative or Negative, he de- duces from the greater or lefs Confonance or Diffonance of the Fibres of rhe Subject and Attribute ; and a right or wrong Judgment in the natural or depraved Tone of the Fibres of the Srain.

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Hence he takes occafion to obferve, that the Fibres of the Srain, from their Analogy to thofe of Mufical Inftru- ments, may be perverted feveral ways ; viz. by being ren- der d too dry or too moift, too ftiff or too lax, (0c In a Phrenly he thinks the Fibtes too dry, and too much dif- tended by the Heat of the Blood, & e . In a Mania tnelc Fibres he thinks too rigid, as well as too dry and dif- tended : In a Lethargy, they ate too much foftcn'd by Phlegm 5 in Idiotifm, or Fooiifhnefs, they are fometimes too loft and fometimes too hard. Laitly, He thinks that in a Melancholy, by the repeated fucceffive Vibrations wmen the attentive Meditation of a Thing induces two or more Fibres, which of themfelves exhibit diffimilar and unequal Ideas, are (the other Parts remaining found) fen- fib y brought to an Ifechronifm : So as the Soul judging well in other refpects, yet in this always makes 'a t'alfc Judgment.

The Srain does not appear abfolutely neceffary to ani- mal Life We have feveral Inftances in Authors, particu- larly m^Philofiphicalfranfaakns, of Children brought forth alive, and lurviving their Birth for fome time, with- out any Srain : And we have Anatomical Inftances, of Animals futviving the lofs of their Srain. Of the firft kind we have a Hiitory from Paris, of a Child, deli- ver d at Maturity ; and living four D..ys, not only without \/rain but even a Bead: instead of both which, was a Mais of Flefli like Liver found. M. Dcnys gives us another Inftancc, of a Child born in itf 73, which, let- ting afidc the Head, was well form'd, but without any Srain, Cerebellum, or Medulla oblongata ■ It had not any Cavity for a Srain, the Skull, if fuch it might be call'd, being folid : Nor was this any way conneaed to the Ver- tebra ; fo that the Marrow in the Spine had no Communi- cation with the Head : The Optic Nerves terminated in the fond Bone. M. le 'Due gives a third Inftancc, in i«9>, where there was neither Cerebrum, Cerebellum, or Medulla oblongata, nor even Spinal Marrow ; the Ca- vity that fhould contain them being extremely fhallow, and full of a black livid Subftance, like congcal'd Blood : He adds, this was the third Subjeft of this kind he had met with Dr. Vrefion, indeed, tells us, that M. in Vemey found here a Spinal Marrow, tho of much lefs Confluence than ordinary ; in which, however, he could di<tin<miih all the four Tunics, and rhe two Subftances ; viz. the Cortical and Fibrous Part, as in the Srain. In a wctd, he takes this to be a Srain it felf, as much as that in the oku 1 ; nay more fo, being more neceffary to Life, and more fenfible, than either the Srain or Cerebellum : A Wound or Compreffion in the firft being always mortal - not lo in the latter, as appears from the Experiments of M. du Vemey and M. Chirac ; the firft of whom took out the Srain and Cerebellum of a Pigeon ; notwithfianding which, it l.v'd, fought Food, had Senfe, and pertbrm'd the common Functions of Life : The latter took out the Srain from a. Dog, yet it liv'd ; upon taking out the Cerebellum it dy d ; but blowing into the Lungs, he obferves, he could keep the Animal alive, an Hour after the Lofs of the Cerebellum. Upon feparating the Medulla oblongata of another Dog from the Spinal Marrow, and removing it with the Srain and Cerebellum, he kept the Dog alive by blowing into the Lungs. To which may be added, many Inftances given by Mr. Boyle ; not only of Animals living a long time after the Separation of the Head from the Body, but even of the Copulation and Impregnation of fome Infects under thofe Circumftances : Whence it ap- pears, that the Spinal Marrow is lufficient, on Occafion. for the Bufinefs of Sanation, Motion, Secretion of Animal Spirits, &c.

BRAN, the Skins or Hulks of Corn "round, ferarated from the Farina, or Flower, by a Sieve. O! Wheat-Bran it is the Starch-makers make their Starch ; which is no- thing elfc but the Fxcula remaining at the Bottom of the- Veffels, wherein the Bran has been ftecp'd in Water. See Starch.

BRANCHES, in Architecture, the Arches of Gothic Vaults. Thefe Arches, traverfing from one Annie to another, Diagonal-wife ; form a Crofs between the 'other Arches which make the Sides of the Square, whereof the Arches are Diagonals. See Vault, Ogive, i£c.

Branches of a Bridle, in the Manage, lira crooked Pieces of Iron which fupport the Mouth-bit, the Chain, and the Curb ; and which are falten'd, on one Side to the Headftall, on the other to the Reins : ferving to keep the Horfes Head under Command. What way foever the Branches of the Bit incline, the Horfe's Mouth alwa\s goes to the contrary. The Duke of Ne-zvcajllc is very particu- lar on the Head of Brandies ; explaining their' feveral Kinds, and their Effects, which are perfectly like thofe of a lever. The Branch is always to be accommodated to the Defign, either of bringing in, or railing a Horfe's Head ; and to the Degree : Accordingly, we have ftrottg and hardy Brand cs, gentle Branches, rude Branches, &c.

With