in Astronomy. See Draco.
DRAGON'S Head and Tail (coput et cauda draconis), are the nodes of the planets; or the two points wherein the ecliptic is intersected by the orbits of the planets, and particularly that of the moon; making with it angles of five degrees and eighteen minutes. One of these points looks northward; the moon beginning then to have north latitude, and the other southward, where she commences south. Thus her deviation from the ecliptic seems (according to the fancy of some) to make a figure like that of a dragon, whose belly is where she has the greatest latitude; the intersection representing the head and tail, from which resemblance the denomination arises.
But note, that these points abide not always in one place, but have a motion of their own in the zodiac, and retrograde-wise, 3 minutes 11 seconds per day; completing their circle in 18 years 225 days; so that the moon can be but twice in the ecliptic during her monthly period, but at all other times he will have a latitude or declination from the ecliptic.
It is about these points of intersection that all eclipses happen. They are usually denoted by these characters, Ω dragon's head, and Ψ dragon's tail.
in Zoology. See DRACO.
DRAGON'S-BLOOD, a gummi-resinous substance brought from the East Indies, either in oval drops wrapped up in flag-leaves, or in large masses composed of smaller tears. It is said to be obtained from the palmijuncus draco, the calamus rotang, the dracena draco, the pterocarpus draco, and several other vegetables.
The writers on the materia medica in general give the preference to the former, though the others are not unfrequently of equal goodness. The fine dragon's blood of either sort breaks smooth, free from any vitible impurities, of a dark red colour, which changes upon being powdered into an elegant bright crimson. Several artificial compositions, coloured with the true dragon's blood, or Brazil wood, are sometimes sold in the room of this commodity. Some of these dissolve like gums in water; others crackle in the fire without proving inflammable; while the genuine sanguis draconis readily melts and catches flame, and is not acted on by watery liquors. It totally dissolves in pure spirit, and tinges a large quantity of the menstruum of a deep red colour. It is likewise soluble in expressed oils, and gives them a red hue, less beautiful than that communicated by anchusa. This drug in substance has no sensible smell or taste; when dissolved, it discovers some degree of warmth and pungency. It is usually, but without foundation, looked upon as a gentle astringent; and sometimes directed as such in extemporaneous prescription against seminal gleet, the fluor albus, and other fluxes. In these cases, it is supposed to produce the general effects of resinous bodies, lightly incrustating the fluids, and somewhat strengthening the solids. But in the present practice it is very little used either externally or internally.
A solution of dragon's blood in spirit of wine is used for staining marble, to which it gives a red tinge, which penetrates more or less deeply according to the heat of the marble during the time of application. But as it spreads at the same time that it sinks deep, for fine designs the marble should be cold. M. Dufay says, that by adding pitch to this solution the colour may be rendered deeper.