280 ANIMAL PHYSIOLOGY. 
viscera) be inspected during the fall in blood-pressure, it may 
be noticed that there is vascular fullness under these circum- 
stances. 
These results are interpreted as being due to afferent im- 
pulses ascending the depressor, acting on the vaso-motor center, 
Pe ASF ow 
T 
Fie. 244,—Curve of blood-pressure resulting from stimulation of the central end of the de- 
pressor nerve. To be read from right to left. 7’ indicates the rate at which the recording 
surface moved, the intervals denoting seconds. At C the current was thrown into the 
nerve, and shut off at O. The result appears after a period of latency, and outlasts the 
stimulus (Foster). 
and interfering with (inhibiting) the outflow of efferent, con- 
strictive, or tonic impulses, which start from the vaso-motor 
center, descend the cord, and find their way to the organs of 
the region in question, in consequence of which the mus- 
cular coats of the arterioles relax, more blood flows to this 
area which is very large, and the general. blood-pressure is 
lowered. 
Again, if the central end of one of the main nerves—e. g., 
sciatic—be stimulated, a marked change in the blood-pressure 
results, but whether in the direction of rise or fall seems to 
depend upon the condition of the central nervous system, for, 
with the animal under the influence of chloral, there is a fall; 
if under urari, arise. 
It is not to be supposed that the change in any of these 
cases is confined to any one vascular area invariably, but that 
it is this or that, according to the nerve stimulated, the condi- 
tion of the centers, and a number of other circumstances. 
Moreover, it is important to bear in mind that with a fall of 
blood-pressure in one region there may be a corresponding rise 
in another. With these considerations in mind, it will be ap- 
parent that the changes in the vascular system during the 
