176 Mtfiellanea Curiofa. 



it felf on the Afpera Arteria and Bronchi, in the 

 lame manner that the Artery does. 



The neceffary confluence of this Difpofition 

 15, that this Artery and Vein being co-extended 

 witft, and faften'd to the Bronchi* muft needs 

 fuffer fuch alteration of Superficial DimenGons, 

 as the Bronchi do in the Elevation or Deprejfion of 

 the Cofta. 



While the Ribs are in a State of Deprejfion 

 (whether before Commerce with the External 

 Air or after ) the Annular Cartilages of the Bron- 

 chi (hrink one into another, and by that means 

 their Dimenfions are exceedingly contracted. In 

 conformity to this condition of the Bronchi, the 

 Pulmonary Artery and Vein muft likewife, ei- 

 ther by means of their Mufcular Coats, con- 

 tract themfelves to the fame Dimenfions, or lye 

 in Folds or Corrugations, which is lefs proba- 

 ble. 



On the other hand, when the Ribs are ele- 

 vated, and the Diaphragm bears downwatd, the 

 Air rufhing into the Lung?, (hoots out the Car- 

 tilaginous Rings, and divaricates the Branches of 

 the Trachea, and by them extends and divaricates 

 the feveral Divifions of the Pulmonary Artery and 

 Veins, and thereby lengthens and enlarges their 

 Cavities. 



This enlargement of their Cavities is very 

 confiderable, not only upon the (core of the 

 addition, which they receive in length there- 

 by, but al(b upon the account of their Divari- 

 cation. For whereas, when the Ribs are de- 

 prefs'd, and the Lungs (ubfide, the Blood- Vet 

 fels are not only contracted, (as I have alrea- 

 dy obferv'd) but their Branches, which are 

 exceeding numerous, approach one another, 



