44° Dr. Philip’s additional experiments on the 
attached to the heart of a frog, and the heart was then cut 
out. On bringing the web of one of the hind legs into the 
field of the microscope, the circulation in it was found to be 
vigorous, and continued so for many minutes ; at length gra- 
dually becoming more languid. 
In endeavouring to proceed farther, I found much difficulty. 
It was not only necessary, in order to ascertain the effect of 
stimuli applied to the nervous system on the vessels of the 
web, to remove the heart, and to lay open the cranium, but 
also to prevent the voluntary motions of the animal, which 
continually occurred, and never failed to accelerate the motion 
of the blood in the web. 
Exp. 13. A frog was deprived of sensibility and voluntary 
motion, by the upper parts of the body being immersed in 
laudanum ; part of the cranium was then removed, after a liga- 
ture had been thrown round the neck to prevent loss of blood. 
The thorax was now opened, and all the vessels attached to the 
heart included in a ligature. But notwithstanding this experi- 
ment was repeatedly performed with the greatest care, the cir- 
culation by all these preparatory means was so enfeebled, 
that although the blood still moved in the web, it was in so 
irregular and uncertain a way, that I never could arrive at any 
positive conclusion respecting the effect of the stimulus ap- 
plied to the brain. After many fruitless attempts, therefore, 
I abandoned this mode of making the experiment. 
Although the action both of the heart and the muscles of 
voluntary motion so influence the effect of stimuli applied to the 
brain, on the circulation in the foot, that, without wholly pre- 
venting the effect of both, no conclusion can be drawn, it is evi- 
dent that the action of the latter cannot increase the effect of 
