. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. 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^. AAAJUUUULAJUUIAJUIAJUUIAJUUUUUUI^^ Fig. 244.—Curre of blood-pressure resulting from stimulation of the central end of the de- pressor nerve. To be read from right to l
. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. 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^. AAAJUUUULAJUUIAJUIAJUUIAJUUUUUUI^^ Fig. 244.—Curre of blood-pressure resulting from stimulation of the central end of the de- pressor nerve. To be read from right to left. T 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 stimvilus (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, a rise. 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- pare
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