\ *. 
[ 2 73 ] 
fions on the pericardium, and the parts which it con- 
tains. 
The firft diftenfion (and this a great and violent 
one) mud: have arifen in the aorta; and the confe- 
quent predure on the pulmonary artery (by the aorta 
fo diftended) mud: have been diffident (either by de- 
grees or at once) to flop the blood’s difcharge out of 
the right ventricle and pulmonary artery, and to di- 
ftend both thofe cavities greatly beyond their natural 
ftate of repletion. So that, under thefe circumftances, 
the two great arteries, and the right ventricle, mud: 
have been under an extraordinary and continued di- 
ftenfion (and, confequently, an increafe of bulk) at 
the lame time; whereas, in the natural ftate of the 
body, thefe three cavities are alternately dilated and 
contraded, and the right ventricle is always propor- 
tionally diminifhed in bulk, as the pulmonary artery 
is increafed, and vice verfa. So that, with refped to 
thefe three great cavities, (fuppodng that their feveral 
diffenfions had been no greater than natural) the pe- 
ricardium mud: have been obliged to contain one third 
more in proportion, than its capacity was formed to 
receive. During this time, the blood being flopped in 
its paftage through the lungs, and its afflux to the left 
auricle and ventricle being thereby fufpended, the left 
auricle and ventricle mud: have remained in a con- 
traded ftate ; in confequence of which, the right ven- 
tricle had ample fpace in the pericardium, to admit 
that degree of diftenfion, which was previoudy requi- 
fite for its burfting. But the right auricle (being fixed 
to its ftation by its connedions w r ith the left auricle 
and the pericardium, and being firmly compreded 
Vol. LI1. Nn againft 
