Abstract
The literature on the vasomotor control of the retinal blood vessels, especially the arterioles, is conflicting. Several authors report that the nervous control of the size of the blood vessels of the retina is in the cervical sympathetic, as is the case in the vessels of many of the other organs of the head. In the rabbit there is agreement, apparently, that the cervical sympathetic controls the size of the retinal vessels. In the higher mammals, however, especially in the carnivora, while some authors report similar control, other investigators obtained negative results. From a practical standpoint as well as from a theoretical one this is an important question; for in man we not infrequently see embolism of the central artery of the retina; and we are constantly seeking further light on the management of these cases.
Our work so far has been done on dogs. We found that stimulation with the faradic current of the central end of the vagus-sympathetic trunk, as a rule, produced narrowing of the retinal arteries and veins. The examination was always made by means of the electric ophthalmoscope. We made attempts to isolate the sympathetic nerve by following the nerves to their ganglia. The stimulation of the isolated sympathetic produced the same results as stimulation of the vagus sympathetic trunk. Section of the cervical sympathetic is followed by slight dilatation of the retinal arteries. In some animals, however, we were unable to see any effects following stimulation or cutting of the cervical sympathetic.
Stimulation of the internal carotid plexus produced marked reduction in the size of the retinal arteries of the same side. Stimulation of the central end of the sciatic nerve produced constriction of the retinal vessels, provided the cervical sympathetic nerves were intact.
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