Page:Cyclopaedia, Chambers - Volume 2.djvu/697

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Dr. Kelly whofe Theory prevails molt in England-, come to be feparated in the Liver, for the firft Time

accounts {or Secretion, from the different Diameters of the preferably to any other Liquor? To this M. Winfim ah-

Veffels, the different Velocity of the Blood, the diffe- iwers, That having obierv'd the Glands of the fmalleft

rent Angles the Ducts make with the Arteries, and the Foetus's to be colour'd, much as in Adults ; it appears

different Attraction of rhe different Parts, under all thele highly probable they had been imbued with thej u i ces

different Circumftances. H.isT'heory fee at length, under theArticle Animal Secretion. But even in this, there is fbmething Arbitrary and Conjectural. Be fid es,t he Reason- ing is carried fuch a Length j that, in aThing the Principles whereof are to obfcure, the Parts or Organs ib impertect- ly known, and the whole Procefs carried on out of Sight, the Mind can fcarce fafely acquiefce in it.

Monf. WinjkWi of the Royal Academy of Sciences, has taken a better Courfe for the Dil'covery of this important Action of Secretion. He does not take up with conjectural Principles, nor draw a plaufible Scheme of Reafoning there- from through the Dark j but applies himfelf to Experi- ment, and investigates, in Nature herielf, and the Structure of the Parts, the Manner Secretion is perform'd in. From a drift Examination of the feveral Kinds of Glands, both in Men and other Animals, he finds, with iome other

they were to filtrate, at the firft Formation of the An.- mal ; or at the fame time when the folid Parts of the Or- gan themfelves were framed.

SECT, a collective Term, comprehending all fuch a s follow the Doctrines or Opinions of fome famous Divine or Philofopher, $$c. The Sects of Philofbphers anion? the Ancients, particularly in ancient Greece, were various. as, Pyrrhonitms, Platomjls-, Epicureans, Stoicks, Peripa^ teticks, Accidemicks t i$c. See each under its proper Ar- ticle. At prefent the Sects of Philofbphy are chiefly rc- duccable to Three, viz. the Cartejians, rhe Peripateticks and the Newmiians, In Theology, the Seffs are much more numerous ; yet the Ancients had Legions now ex- tant, as, Mamchees, GnojUcks, Mmtmiifis, ££>c. 'I he prin- cipal now on Foot, are rhe Lutherans, Calvhrifts., An&b&pi tiffs, Arians, Sccinians, Arminians, £$c. The Rife, Pro-

Anatomifts, that the Glands are only Pelotoons or Plexus's grefs,_ and Fate, with the diitinguifhing Characters and

of VefTels: but the VefTels proper to the Gland, and which conflitute the principal Part thereof, M. Wmjlow firft difcovered ro be Tubes, furnifhed, on the Infide, with a kind of Down or Tuft, or rather a very fine, fpongeous Tiffue, which fills the whole Cavity of thole VefTels like a Pith or Marrow. This he finds in all Glands, of all Animals; In different Glands, 'tis found of different Colours, and this different Colour is even found in the different Glands of Fcetus's themfelves.

The Gland, ther, is, at leaftits main Part, a Compound of thefe downy c o'r lpongeous VefTels, which, from their Office, we will call Secretory VeJJels or Bafts, and which

Opinions of each 5 See under its refpective Head.

SECTA, in Law. See Suit.

SECTIO, or Operatio Cafarea, See Caesarian Sec- tion.

SECTION,> Part of a Thingdivided ; or the Divifion itfelf: Such, particularly, are the Sub-divifions of Chap- ters, by others called Articles. The Mark of a StBion is i The Ancients difregarded the Dividing of their Books into Chapters and SeclionSj that was a Task left for future Editors, and Criticks. The Word is form'd from the Latin, feco, I cut.

Section of a Building, is its Profh ; or a Delineation

frequently do, almoft of themfelves, form what we call a of its Heights and Depths raifed on the Plan 5 as if the Gland or glandu/oiis Body: Tho' befide thefe Veffels,we ufu- T ' ' ' ally remark Four other Kinds, viz. Arteries, Veins, Excre- tory Ducts and Nerves. The Secretory Ducts we diflin- guifh from the Excretory Ones; in that the former, by the peculiar Texture of their Down, ferve to feparate a par- ticular Liquor ; and that the latter only ferve to receive the Liquor thus Secreted, and to carry it to the Place 'tis deftined for. For a more particular Account of the Stru- cture and Organization of the Glands, See Gland.

For the Manner wherein the Glands act, in feparating the feveral Liquors from the Body, M. WtnfloW lays it down thus : 'Tis a Thing well known by Phyficians and Chy- miits, that a Piece of brown Paper, which is only an Affemblage of fmall Filaments drawn cloie to each other, having once imbibed Oil or Water, will never let any other Liquor pafs through it, but of the fame Kind with what 'tis impregnated withal. All others it {tops. And the like is oblerved of a Wick of Cotton or other Matter, which having firft imbibed its Fill of Oil or Water, and

Fabrick was cut afiinder, to difcover the Infide. See Profile.

Horizontal Section. See Ichnography.

Section, in Geometry, a Side or Surface appearing ot a Body, or Figure cut by another; or the Place wherein Lines, Planes, &c. cut each other. The common Setlicu ot two Planes is always a right Line, being the Line fup- pofed to be drawn by the one Plane in its cutting or enter- ing the other. See Plane. If a Sphere be cut in any. manner, the Plane of the Section will be a Circle, whofe Centre is in the Diameter of the Sphere. See Sphere. The Setlicns of the Cone are Four, viz, a Circle, Parahle, Hyperbole and Ellipfis. See each under its proper Ar- ticle. See alfb Cone.

Conic Sections. See Conic Section.

SECTIONES SEQUENTES, in Conies, a Term, whofe Import may be thus conceiv'd : Suppofe Two Right Lines, as A B, CD (Tab. Conicks Fig. j.) mum. ally interfering one another in E, which Point E, is fiip-

being then dipp'd at one End, in a Veffel full of Oil and pofed to be the common Centre of the oppofite Hyperbolic

Water together 5 the Wick that had imbibed the Oil, will only raife and diftil Oil, and that with Water, only Water. Now, in the Secretory Duels of the Glands, we find a Parallel Structure ; an Affemblage or Tiffue of fine Threads or Filaments bound dole together, much as in brown Paper, or a Cotton-wick ; only differently difpofed. ThisTiffue, then, having once imbibed a certain Juice, will not let pafs any of the Liquors which arrive at the Orifices of thefe Ducts, but that it had firft imbibed. The Caufe

Sections, FG, HI, and whofe common Afymptotes, the propofed Lines A B, C D alfo are. In this particular Cafe, the Seblions G F and H I, are called Seffiones S;quentes t becaufe they are placed following one another in the con- tiguous Angles of Two interfering Right Lines : And if the determinate Diameter H G, of one of the SetliontS Seqttentes (which is coincident with rhe fuppofed indeter- minate Diameter of its oppofite) be equal ro the vertical Tangent K L, applied between the Afymptotes in the

of this Phenomenon, is doubtlefs, to be referr'd to the Point G, of the Diameter G F, then, Apollonius calls fuch

great Principle of Attraction, which is found ftronger be- SeBions, Conjugate Setlio72S.

tween the Homogeneous than the Heterogeneous Parts of SECTOR, in Geometry, a Part of a Circle cGmpre-

the fame Fluid. But this is an Enquiry that belongs to hended between two Radii, and the Arch. Thus the

another Place, See Attraction and Repulsion. mix'd Triangle A C D (Tab. Geometry Fig, 13.) compre-

As the Blood, now, is not a Homogeneous Liquor 5 but hended between the Radii A C and D and the Arch A D,

a Compound of an Infinity of different Parts or Mole- is a Setlor of 'the Circle.

cules, fome Oily, others Mucilaginous, Aqueous, Saline, 'Tis demonflrated by Geometricians, that the Setlor of

Subtile, Grofs, &c. in its Motion along the Arteries of the Gland, it becomes divided into all the little Ramifica- tions thereof; by which Means its Velocity is exceedingly abated, and its Molecules obliged to go off one by one, through the narrow Paffage of the Artery into the Vein, and of confequence to pafs over the Orifices of the Secre- tory 1)uUs of the Glands, whofe Down is already tinged With a Juice of a certain Nature. Such of the Molecules

Circle, as A CD, is equal to a Triangle, whofe Bafe is the Arch A D, and its Altitude the Radius A C.

If from the common Centre of Two Concentric Circles, be drawn Two Radii, to the Periphery of the Outer, the Two Arches included between the Radii, will have the fame Ratio to the Peripheries ; and the Two Setlors, the lame Ratio to the Areas of their Circles.

To find the Area of a Seftor DCE ; the Radius of the

therefore, as arc found of the fame Nature with the Juice Circle CD, and the Area DE being given: To 100,

they meet withal at the Entrance of the Secretory 2)utl t 3 14 and the Radius A C, find a Fourth propotional Num-

joyn themfelves to them, and enter the Ducts, driven on ber 5 this will be the Semi-periphery. Then to 180, &c

by others that follow them, Thus they pafs, fucceffively, given Arch D E, and the Semi-periphery juft found, find

through the whole Veffel, and at length go out of it into another fourth Proportional ; this will give the Arch A B

the Excretory Duct, while the reft, which are of adiffe- in the fame Meafure in which the Radius AC is given.

tent Kind, run over the Orifice of the Secretory Veffel, Laftly, multiply the Arch DE into the Semi-radius, the

without ever mixing with the Juice thereof, and thus Product is the Area of rhe Sector.

arriving in the Vein, are carried back to the Heart. Sector is alfo a Mathematical Inftrument, of great Ufe

All that remains, is, to explain how thefe Parts mould in finding the Proportion between Quantities of the fame

have firft imbibed the particular Juices neceffary for their Kind, as between Lines and Lines, S jrfaces and Surfaces,

refpcSUve Secretions; How, for Inftance, the Bile fhould ££c. whence the French call it the Compafs of Proportion*