( «78 ) 
through all the Extent of the Left Lobe of the Langs. 
The other Pulmonary Branch going out of the Left fide 
of its Trunk, turns itfelf over immediately crofs upon* 
the other Arteries, from the Right to the Left, to joyn 
the Aorta Inferior dextra , till it has pierced the Peri - 
cardium , where it joyns to the Right Branch of the 
Trachea Arteria , which it accompanies through the 
whole extent of the Right Lobe of the Lungs, 
One thing feems to. me very retnarkable in this Pul- 
monary Artery 5 it is this, that though its Trunk, in 
going out of the Heart, hath more than twice the Dia- 
meter of the Arteria Aorta f/nijira, yet the two Branches 
which it fends to the Lungs, have not either of them 
one third ot he Diameter of the aorta, finifira. ' In the 
Arteries, which I have fill’d with Wax, the Trunk of 
the Pulmonary Artery hath between feven and eight 
Lines Diameter 5 the Aorta Jiniftra four and. a ii j and 
.the Pulmonary Benches* aftpr having pierced ’the Peri- 
cardium, have not either of them but one Line and a 
half Diameter : Nevertfieleis ,'h s Artery doth not pro- 
duce any other Branchy alf ihe Blood, which enters 
from the Heart into its Trunk,’ is carried into the two 
Lobes of the Lungs, and no wnereelfe. The reafon of 
fuch difproportion I cannot guefs; but this is matter of 
Fad, fince it is tiie fame in all : Neverthelefs, if I may be 
permitted to conjedure, it feems to me that it may be 
attributed to the alteration that happens to the Branches 
of the Trachea Arteria , when the Tortoife ftretcheth 
forth his Head out of the Shell 5 for thefe Pulmona- 
ry Branches making an half Circle before they joyn 
with the Trachea Arteria , when the Animals Head is 
drawn in, the Extenfion which happens to the Branches 
of the Trachea Arteria when the Animal goes out of the 
Shell, turns thefe half Circles into (harp Angles ; info- 
much, .that thereby the Paflfage of the Blood is fome. 
what Interrupted, and confequently the Blood, which 
pafles 
