73 
on which the action of the heart depends , &c. 
ruption of respiration. The circulation is particularly apt to 
fail, if artificial respiration is not carefully performed after 
the animal ceases to breathe. In making such experiments, 
after opening the bone, it is always necessary to ascertain 
whether the circulation continues, before we destroy or re- 
move the brain or spinal marrow. As little blood is lost in 
this part of the operation, when the carotid arteries were beat- 
ing before, we always found them beating after it. The result 
of this experiment is still more striking in the cold blooded 
animals, in which death takes place so slowly, that the circu- 
lation continues long after the total destruction of the nervous 
system. 
Exp. 10. The brain of a frog and the spinal marrow as low 
as the dorsal vertebra* were laid bare. The thorax was then 
opened, and the heart found acting vigorously ; and from the 
transparency of its sides, the passage of the blood through it 
distinctly seen. The part of the spinal marrow, which had 
been laid bare, was then removed, but without at all affecting 
either the motion of the heart, or the passage of the blood 
through it. The brain was then removed, with the same 
result. 
Exp. 11. The brain and spinal marrow of a frog were 
wholly removed. On opening the thorax, the heart was 
found performing the circulation freely. 
I have already had occasion to observe, that it is generally 
admitted that the action of the heart cannot be influenced by 
stimuli applied to the nervous system : and it seems almost a 
contradiction to suppose that it should, when we see that it 
cannot be influenced by the total destruction of this system. 
There were many reasons, however, which induced me to try 
MDCCCXV. L 
