SECT. XVII. PHYSIOLOGY. 135 
are greatly enlarged in gestation; and Broussais 
maintains, that the stomach is in the lowest state 
of inflammation during digestion. The expan- 
sion of the arteries, in these organs, in the above 
circumstances, is in part due to the vital force; 
but in part also it seems attributable to me- 
chanical distention, and removal of incumbent 
pressure. 
cecxxv. As to the collections of fluid in the 
thorax, they seldom occur in both its divisions 
at once, to any great extent, without causing 
death ; and one lung is capable of performing the 
function of respiration. In such a case, I once 
found the pulse even fuller and stronger than 
natural; but who would imagine, from this cir- 
eumstance, that the lung which was consumed, 
had been of no use while it remained entire ? 
_ cccxxvi. But what is the effect of expansion 
of the lungs at birth? In the foetus, the lungs 
are collapsed into very small dimensions; and 
the blood, instead of passing wholly along the 
pulmonary artery, passes in great part into the 
aorta, by the ductus arteriosus ; but no sooner do 
the lungs expand after birth, than blood ceases to 
flow by the ductus arteriosus, and rushes. entirely 
along the branches of the pulmonary artery. It 
seems to me, that cause and effect cannot be more 
closely allied, than this new direction of the blood 
from expansion of the lungs. 
