tc>4< Mr.. Abernethy's Observations on 
Anatomists appear to have been much perplexed concerning 
these foramina Thebesii ; even Haller, Senac, and Zinn, 
were sometimes unable to discover them ; which suggested an 
idea, that when an injection was effused into the cavities of the 
heart, the vessels were torn, and that it did not escape through 
natural openings. When these foramina were injected, they 
were found under various circumstances, as to their size and 
situation ; and Haller observed, that the injection, for the 
most part, escaped into the right cavities of the heart. It also 
remains undetermined, whether these foramina belong both to 
the arteries and veins, or respectively to each set of vessels. 
It is from an examination of these openings in diseased sub- 
jects, that a solution of such difficulties may probably be ob- 
tained. Whoever reflects on the circumstances under which 
the principal coronary vein terminates in the right auricle of 
the heart, will perceive that an impediment to the flow of 
blood through that vessel must occasionally take place; but 
the difficulty will be much increased, when the right side of 
the heart is more than ordinarily distended, in consequence of 
obstruction to the pulmonary circulation. Indeed it seems pro- 
bable, that such an obstruction, by occasioning a distended 
state of the right side of the heart, and thus impeding the 
circulation in the nutrient vessels of that organ, would as ne- 
cessarily occasion corresponding disease in it, as an obstruction 
to the circulation in the liver occasions disease in the other ab- 
dominal viscera, were it not for some preventing circumstances, 
which I now proceed to explain. 
Having been attentive to some very bad cases of pulmonary 
consumption, from a desire to witness the effects of breathing 
medicated air in that complaint, I was led to a more particular 
