TRANSACTIONS OF THE SECTIONS. 
91 
when the respiratory movements are suspended. But to this obser¬ 
vation it might be objected, that the animals on which experiment had 
been made had been allowed to remain in the azote until they became 
insensible, and their respiration of course ceased, and had not been 
examined until some minutes after their apparent death, and it might 
be said, that the right side of the heart had become congested only 
after the acts of respiration had ceased, and in consequence of their 
cessation. 
In order to avoid this source of fallacy several rabbits were con¬ 
fined in azote, only until their breathing became laboured, the re¬ 
spirations generally less frequent, but much longer and fuller 
than natural. They were then taken out and instantly struck on 
the head with such force as to crush the brain and cerebellum, and 
arrest the circulation as instantaneously as possible. This was always 
attended with violent and general convulsion, but with no attempt 
at respiration, sensation being apparently instantaneously suppressed. 
When the body was opened immediately after the convulsion had 
subsided, the right side of the heart was always found distended 
with blood, and palpitating feebly; the left side at rest and compa¬ 
ratively empty: the quantity of blood obtained by puncturing and 
pressing the right side and pulmonary artery was from 5 to 10 times 
as much as could be obtained from the left side and aorta. When 
a rabbit previously breathing naturally was killed in the same man¬ 
ner, the quantity of blood on the right side of the heart (apparently 
accumulating there during the convulsions) was found to be greater 
than on the left; but the difference was decidedly less than when 
it had been breathing azote; and in one of these comparative trials 
the blood in the left side was found to be sufficient to keep up a 
feeble palpitation in that side, whereas in the animals that had 
breathed azote the left side was always found quite at rest. 
It appears from these experiments that when oxygen is not ad¬ 
mitted into the lungs in inspiration, even although the respiratory 
movements continued further and more forcible than usual up to 
the moment of death, the blood stagnates on the right side of the 
heart; and that the application of oxygen to the blood at the lungs 
is a cause of acceleration of its movement through the lungs, inde¬ 
pendently of any influence of the mechanical movements of respi¬ 
ration. 
If we further inquire, imwhat manner oxygen can give this sti¬ 
mulus to the flowing blood through the lungs, it appears certain 
that it cannot be by stimulating the small capillaries of the lungs 
(the only vessels to which it is directly applied) to contraction, be¬ 
cause even if it be granted that there are vessels capable of con¬ 
tracting on irritation (which is very doubtful), the immediate effect 
of stimulating any arteries capable of taking on such action has 
always been observed to be a constriction permanent for some 
length of time, and in consequence a retarded flow of the fluids 
through them, as in the experiments of Wedmeyer. 
If, again, we suppose the effect of the oxygen on the minute ves- 
