2S The Jnafomy of a HOKSE. Chap.IIL 



Cavity of the Cheft, being divided into two Lobes, one 

 of which lies on the right Side of the MediaJ^inumy and 

 the other on the left. 



They are compofed of the various Ramifications, or 

 Branchings of the Veins, Arteries, and Nerves, together 

 -with the Windpide, the Extremities of whofe Branches 

 are very finely wove together, fo as to form an infinite 

 number o{\\.Vi\Q'VefuleSy or Air-bladders^ refembling fmall 

 Grapes when they are extended, but not very perceiveablc 

 at any other time. When an Animal fucks in the Air, 

 thefe Httle Vejicula; or Bladders, are then dilated and full ; 

 and when the Air is emitted, as in Expiration, they be- 

 come empty, 



The Wmdp'ipe, ^^^ JViftdpipSy whofe Branches make up 

 a great part of the Subllance of the Lungs, 

 is that great Chanel, which beginning at the Root of the 

 Tongue, defcends down the Throat, and, as foon as it 

 reaches the Lungs, divides itfelf into two large Branches, 

 one to each Lobe. Thefe fend off a great many Branches, 

 which detach an infinite number of other Branches that 

 reach into all Parts, and whofe Extremities open into the 

 Veficula^ or Bladders above defcribed. This Pipe is 

 called the Trachea^ or 'Jjperia Artevia^ from its rough- 

 nef^, which Name it obtains from the Throtle to the 

 tungs ; but thefe Branches which it fends ofT into each 

 Lobe, are term'd its Bronchia. 



It is compofed of a double Membrane, which inclofes its 

 Circular Rings^ the innermoft of which being mufcular, 

 made up of llreight and oblique Fibres, it thereby con- 

 traifts and dilates itfelf in the A6tion of Breathing. Thofe 

 Rings do not quite encompafs the Trachea^ or Afpsra 

 j'h'teria^ but leave a fourth Part of the Circle wanting, 

 left they fhould hurt the Gullet whereon it lies, and occa- 

 iicn Pain in fwallowing ; but after it divides itfelf into its 

 Bronchia, they go quite round every Branch of it, fo far 

 as is perceivable to the naked Eye ; and doubtlefs, hold 

 ihe fame form where its Branches are the moft minute 

 and iinall. Thefe Rings, being in a great meafure, carti- 

 laginuus, indue the whole Windpipe, and all its Branches, 

 With a fort of Elafticity or Spring, whereby it ads in 

 concert v/ith its membranous and m.ufcular Parts. 



The Blood- vefiels, which alfo compofe a 



^r/ S^^^^ P'^^^ ^^^ ^^^ ^"^^^ ^'*^^" Lungs,are partly 



*^'^^ ^' a Branch from .the great Artery, but pnnci- 



♦ " pally 



