In the making of these powders, the oil and the magnesia ought to be well mixed and allowed to remain for half-an-hour, then reduce the mass to fine powder, and keep it in glass bottles with stoppers.
These medicines, by their local application, increase the circulation, and give a greater supply of blood to the deficient organs, and thereby produce natural tone and power. They are equally useful in removing chronic diseases, where thickening and opacity have taken place, by rousing into activity the absorbent and nervous influence by their stimulating power. Among many others possessing the same power, is a concentrated tincture of pepper nigrum, ginger, &c.
The internal administration has been found much more serviceable in chronic diseases of the eye, such as opacities, &c., than in amaurosis.
The manner of using the embrocations is, by rubbing the forehead and temples with a sponge saturated with the liquid. This plan alone, kept up daily, is beneficial; but the efficacy is more than doubled if another sponge, with warm or cold water, is rubbed upon the forehead for a minute afterwards. By this the energy of the medicines in inducing a free circulation is greatly augmented, and greater warmth is rapidly developed. The rationale, in my opinion, is, that the large quantity of carbon in some of the essential oils, and its solubility in alcohol, permits it, by the friction, to pass through the cuticle and unite with the oxygen. As the oils are very insoluble in water, and as the alcohol has a strong affinity for the water, the carbon is more readily disengaged, and forms a union with the oxygen in the vessels, and thereby produces heat and great activity of circulation. I have no doubt that that is the reason why many bodies are so pungent, when put into the mouth. I have only given two cases—viz., John Plunkett and William Dale—as illustrative of the action of the essential oils.
It will be seen in the following extract from Tyrrell on the Eye, "Functional amaurosis arises from a deficient supply of red blood." He says—
"In these cases there always exists, I believe, a want of general power and vigour of circulation at first; but in some instances of long-continued affection of this kind, the local circulation never regains its proper force and fulness; and the supply of blood is inadequate to support the functions of the part, although the general system recovers its natural tone and power."
I think this statement very correct, and therefore the embrocations producing so much additional circulation, point out at once the essential oils, along with the water, as its proper remedy. I here quote Magendie, who corroborates the plan which I adopt—viz., the medicines being most useful when applied to the forehead and temples in amaurosis:—
EXTRACTS.
"Lectures on the Physiology of the Nervous System, delivered in 1836, in the College of France, by Majendie."—Lancet, April 29th, 1837, page 186.