M. M. If the squinting has not been confirmed by long habit, and one eye be not much worse than the other, a piece of gauze stretched on a circle of whale-bone, to cover the best eye in such a manner as to reduce the distinctness of vision of this eye to a similar degree of imperfection with the other, should be worn some hours every day. Or the better eye should be totally darkened by a tin cup covered with black silk for some hours daily, by which means the better eye will be gradually weakened by the want of use, and the worse eye will be gradually strengthened by using it. Covering an inflamed eye in children for weeks together, is very liable to produce squinting, for the same reason.
[5]. Amaurosis. Gutta serena. Is a blindness from the inirritability of the optic nerve. It is generally esteemed a palsy of the nerve, but should rather be deemed the death of it, as paralysis has generally been applied to a deprivation only of voluntary power. This is a disease of dark eyes only, as the cataract is a disease of light eyes only. At the commencement of this disease, very minute electric shocks should be repeatedly passed through the eyes; such as may be produced by putting one edge of a piece of silver the size of a half-crown piece beneath the tongue, and one edge of a piece of zinc of a similar size between the upper lip and the gum, and then repeatedly bringing their exterior edges into contact, by which means very small electric sparks become visible in the eyes. See additional note at the end of the first volume, p. 567. and Sect. XIV. 5.
M. M. Minute electric shocks. A grain of opium, and a quarter of a grain of corrosive sublimate of mercury, twice a day for four or six weeks. Blister on the crown of the head.
[6]. Auditus imminutus. Diminished hearing. Deafness is a frequent symptom in those inflammatory or sensitive fevers with debility, which are generally called putrid; it attends the general stupor in those fevers, and is rather esteemed a salutary sign, as during this stupor there is less expenditure of sensorial power.
In fevers of debility without inflammation, called nervous fevers, I suspect deafness to be a bad symptom, arising like the dilated pupil from a partial paralysis of the nerve of sense. See Class [IV. 2. 1. 15].
Nervous fevers are supposed by Dr. Gilchrist to originate from a congestion of serum or water in some part of the brain, as many of the symptoms are so similar to those of hydrocephalus internus, in which a fluid is accumulated in the ventricules of the brain; on this idea the inactivity of the optic or auditory nerves in these fevers may arise from the compression of the effused fluid; while the torpor attending putrid fever may depend on the meninges of the brain being thickened by inflammation, and thus compressing it; now the new vessels, or the blood, which thickens inflamed parts, is more frequently reabsorbed, than the effused fluid from a cavity; and hence the stupor in one case is less dangerous than in the other.
In inflammatory or sensitive fevers with debility, deafness may sometimes arise from a greater secretion and absorption of the ear-wax, which is very similar to the bile, and is liable to fill the meatus auditorius, when it is too viscid, as bile obstructs the gall-ducts.
M. M. In deafness without fever Dr. Darwin applied a cupping-glass on the ear with good effect, as described in Phil. Trans. Vol. LXIV. p. 348. Oil, ether, laudanum, dropped into the ears.
[7]. Olfactus imminutus. Inactivity of the sense of smell. From our habits of trusting to the art of cookery, and not examining our food by the smell as other animals do, our sense of smell is less perfect than theirs. See Sect. XVI. 5. Class [IV. 2. 1. 16].
M. M. Mild errhines.