Bronchi, in the same manner that the Artery does.
The necessary confluence of this Disposition if, that this Artery and Vein being co-extended with, and fasten'd to the Bronchi, must needs suffer such alteration of Superficial Dimensions, as the Bronchi do in the Elevation or Depression of the Costæ.
While the Ribs are in a State of Depression (whether before Commerce with the External Air or after) the Annular Cartilages of the Bronchi shrink one into another, and by that means their Dimensions are exceedingly contracted. In conformity to this condition of the Bronchi, the Pulmonary Artery and Vein must likewise, either by means of their Muscular Coats, contract themselves to the same Dimensions, or lye in Folds or Corrugations, which is less probable.
On the other hand, when the Ribs are elevated, and the Diaphragm bears downward, the Air rushing into the Lungs, shoots out the Cartilaginous Rings, and divaricates the Branches of the Trachea, and by them extends and divaricates the several