relation between the nervous and sanguiferous systems. 441 
sedatives; and the sedative lessening the power of the heart 
will not affect the result of the experiment, if it be made on 
the web cf the frog. We have just seen, that the total 
ceasing of the action of the heart, does not for a considerable 
time affect the circulation in it. The following experiment 
appears to be decisive of the effect of the sedative, and of the 
stimulus, as far as this can be decisive, the action of the heart 
remaining. It is evident that the action of either stimulus or 
sedative is equally conclusive respecting the direct influence 
of the nervous system on the blood vessels. 
Exp. 14. Part of the cranium of a frog was removed, the 
web of one of the hind legs brought into the field of the 
microscope, and the circulation in it observed. The animal 
was now rendered insensible by the immersion of the other hind 
leg in laudanum. The insensibility did not in the least affect 
the circulation in the web before the microscope. Spirit of 
wine was then applied to the brain with an evident increase 
of the velocity of the blood in the web. The same effect 
was produced in a less degree by watery solutions of opium 
and tobacco. After the tobacco had been applied for about 
half a minute, the motion of the blood was much less frequent 
than before its application. On washing off the tobacco the 
velocity of the blood increased, and was again lessened on 
applying it. This was repeated several times with the same 
effects. The following way of performing the experiment, 
is equally conclusive. 
Exp. 15. A frog was rendered nearly insensible by having 
its back immersed in laudanum. A ligature was then thrown 
round the neck to prevent loss of blood, part of the cranium 
mdcccxv. 3 L 
