Role of the Sympathetic in Lacrimal Secretion.

THI lacrimal gland is innervated by the lacrimal, the facial, and the cervical sympathetic nerves; the anatomical and functional characteristics of each were briefly summarized in a previous communication (Whitwell, 1958). Overwhelming evidence points to the fact that the lacrimal nerve is not secretory in function, but is purely the afferent path ofa reflex arc. Similarly, the facial nerve is of prime importance in the control of lacrimation, especially the reflex tear secretion. Nevertheless, in clinical cases of complete paralysis of the facial or greater superficial petrosal nerves, although weeping is abolished, the eye remains comfortably moist (Rowbotham, 1939). The problem of the residual secretion remains undecided. It is possible that the completely denervated gland autonomously secretes a constant small amount of tears, or that a blood hormone is the stimulating factor. It is equally possible that the sympathetic nervous system is responsible. The literature on the role of the sympathetic in tear secretion is both contradictory and confusing. Herzenstein (1868) cut the cervical sympathetic in dogs and noticed no alteration in tear secretion, as also when he stimulated the upper cut end. Wolferz (1871) in dogs, and Demtschenko (1871) and Laffay (1896) in rabbits, all obtained lacrimation on stimulation of the cervical sympathetic, even after section of the lacrimal nerves. Tepliachine (1894) obtained similar results. In a detailed study, Reich (1873) stimulated the distal end of the cut cervical sympathetic. In five rabbits, increased lacrimation was noticed, but in four there was no effect. In seven rabbits, removal of the superior cervical ganglion had no effect on the reflex lacrimation caused by nasal mustard-oil stimulation. In six rabbits, after removal of both superior cervical ganglia and the trigeminal on one side, it was still possible to obtain reflex lacrimation. Experimenting on monkeys, Campos (1897) noticed no effect by stimulating the cervical sympathetic. Vulpian (1875) found that section of the cervical sympathetic or removal of the superior cervical ganglion of cats and dogs may give an increased tear secretion, but not constantly. In some dogs, curarized and under artificial respiration, removal of the left superior cervical ganglion caused a more abundant secretion from the right eye. In