VOL. LII.] PHILOSOPHICAL TRANSACTIONS. 577 



extraordinary and violent distention, immediately antecedent to the bursting of 

 the ventricle, is evident, from the recent fissure of the aorta, and the consequent 

 extravasation of blood between its coats. Now as this increased and violent dis- 

 tention of the aorta must have been attended with a proportionate pressure on the 

 pulmonary artery, and consequently an increased opposition to the passage of the 

 blood out of the right ventricle ; so that distention of the aorta must be consi- 

 dered as the immediate cause of the right ventricle's being surcharged with blood, 

 and consequently of its bursting. 



The immediate cause of this distention of the aorta, as also of its being deter- 

 mined to that particular time, are naturally explicable, from his Majesty's having 

 been at the necessary-stool ; as the office then required cannot be executed but 

 by such a pressure on all the contents of the lower belly, and consequently on 

 the great descending artery, as must of necessity subject the trunk of the aorta, 

 and all its upper branches, to a surcharge with blood continually increasing, in 

 pro})ortion as the pressure may happen to be continued longer, or exerted with 

 greater violence, inconsequence of a costive habit, or any other resistance. 



As to the 2d question ; viz. how it could happen that the blood should force 

 its way rather through the side of the ventricle than of the auricle ? since it is 

 well known that when the ventricle is fully distended with fluids, they will easily 

 pass back into the auricle ; so that under such a distention as the ventricle must 

 have suffered before it burst, it should seem to have made one continued cavity 

 with the auricle ; of which cavity, the auricle being by much the weakest part, 

 must have been the most liable to a rupture. This certainly is the circumstance 

 in which the very great singularity of the case before us consists ; and many 

 difficulties offer against any obvious explanation. 



Two circumstances however seem to throw some light on this obscure and 

 difficult question. The first consists in the texture, connexions, and capacity of 

 the pericardium ; the 2d in the order in which the several surcharges must have 

 arisen. 



The pericardium is a strong tendinous membrane, inelastic in every direction, 

 containing the 2 auricles, the 2 ventricles, and the 2 great arteries, as in a purse ; 

 it is fixed to its contents at the back of the 2 auricles, where, by its connexion, 

 it surrounds the 2 venae cavae : hence, passing along the arch formed by the aorta, 

 it descends to the pulmonary artery, and continues round the orifices of the pul- 

 monary veins, firmly attached to these several parts in its passage. By these con- 

 nexions, these parts are all fixed in their several stations, incapable of separating 

 from each other, or shifting their situations, however they may happen to be 

 compressed. The pericardium is generally said to serve as a defence to the 

 heart ; but that defence seems to consist chiefly, in preventing the right auricle 

 from being stretched by the depressions (or complanations) of the diaphragm in 



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