Chap. III. The Anatomy ^/^ HORSE. 29 



pally the Pulmonary Artery and Vein : Thefe Veins and 

 Arteries have frequent Inofculations, or Communications 

 one with another, by which means they become curiouily 

 interv/oven towards thofe Vepiculie^ or Air-bladders abo\'^- 

 mention'd, which kind of Structure is, by moil Anato- 

 mifts, beiiev'd to be, to the end that every minute Particle 

 of the Blood in thofe Parts may be impregnated with Air. 



There are, befides thefe, abundance of Lymphaticks, 

 which attend on the Veins and Arteries thro' the whole 

 Surface of the Lungs, to receive the fuperfluous Moifture 

 fcparated by the Glands, which they afterwards difcharge 

 into the Thoraick Du^. The Lungs have alfo Nerves, 

 which fpring from the recurrent Branches of th€ wandring 

 Pair. Thefe accompany the Blood- veflels thro' their whok 

 Subftance, and are divided into innumerable BraiKhes. 



As to the Ufe of the Lungs, it is evident „, . jj^ 

 from what has been already faid, that they ^^^ -^^^ 

 are the chief Organs of Refplration, being in every refpe^ 

 fuited to receive the Air, which js the proper Element for 

 all Quadrupeds, as well as Man, to breathe in : And as the 

 Windpipe, with all its Branches, is, made up of cartilaginous 

 Rings, which a6t in concert with its mufcular Coat ; it 

 thereby becomes endu'd with a fort of Elajiicity or Spring, 

 by which it is extended as often as the Air is drawn in, and 

 in Expiration becomes again contradted. This fort of Me- 

 chanifm is plainly vifible in the Windpipe of any Animal, 

 which being drawn out to its full Length, immediately 

 gathers itfelf up as foon as the Force whereby it was ftretch- 

 €d is remov'd. The Elevation and Deprellion of the Chell 

 is in like manner occafion'd by the Extention and Contrac- 

 tion of the Lungs ; and as its Adtion is thus fubfervient to 

 them in Refpiration, it feems alfo to be chiefly derived from 

 them -y fo that the Air may be properly term'd the princi- 

 pal, tho' not the immediate Caufe of that Adion alfo. 



Now as we are fure the Air is the immediate and princi- 

 pal Caufe of that Refpiration, it w^ould be to little purpofe 

 to fpend Time about the various Opinions concerning that 

 Motion of the Lungs, to wit, whether it be Natural or 

 Animal, as the Philofophers term it ; or whether, according 

 to fome, it be partly Natural and partly Animal : I fbill 

 only therefore obferve, that altho' it is fomewhat in our 

 Power to regulate that A6lion, by drawing in more or lefs 

 Air at pleafure, yet we are very well fatisfied no Creature 

 can imprifon it in the Lungs, or keep it out two Minutes, 



with- 



