something that relates to the kidneys. See Kidney.

Nephritic Wood, (lignum nephriticum), a wood of a very dense and compact texture, and of a fine grain, brought to us from New Spain in small blocks, in its natural state, and covered with its bark. It is to be chosen of a pale colour, sound and firm, and such as has not lost its acid taste; but the surest test of it is the infusing it in water: for a piece of it infused only half an hour in cold water, gives it a changeable colour, which is blue or yellow, as variously held to the light. If the vial it is in be held between the eye and the light, the tincture appears yellow; but if the eye be placed between the light and the vial, it appears blue. We often meet with this wood adulterated with others of the same pale colour; but the dusky black hue of the bark is a striking character of this.

The tree is the coatli of Hernandez. It grows to the height of our pear-tree, and its wood while fresh is much of the same texture and colour; the leaves are small and oblong, not exceeding half an inch in length, or a third of an inch in breadth; the flowers are small, of a pale-yellow colour, and oblong shape, standing in spikes: the cups they stand in are divided into five segments at the edge, and are covered with a reddish down. This is the best description of the tree that can be collected from what has been hitherto written of it; nobody having yet had an opportunity of taking its true characters.

This wood is a very good diuretic, and is said to be of great use with the Indians in all diseases of the kidneys and bladder, and in suppression of urine, from whatever cause. It is also recommended in fevers, and in obstructions of the viscera. The way of taking it among the Indians is only an infusion in cold water.

Nephritic Stone, a soft, brittle, opaque stone, not susceptible of a good polish; smooth, and, as it were, unctuous to the touch; variegated with several colours, of which green is the principal. It is found in Saxony, Bohemia, Switzerland, Spain, and Mexico; and from the imaginary virtues ascribed to it in nephritic disorders, has been ranked among the precious stones, but differs exceedingly from them in all its sensible qualities. Neumann finds fault with some authors for referring this stone to the jaspers, agates, or marbles; from all of which, he says, it widely differs: it wants the red specks of the jaspers, the hardness and compactness of the others, and all of them want its unctuous or soapiness. Out of 60 grains of nephritic stone, vinegar dissolved three; oil of vitriol seven; spirit of vitriol 14; spirit of nitre 16; aqua regia 18; and spirit of salt 20. The spirit of salt acquired a greenish-yellow tincture; aqua regia a gold yellow; oil of vitriol a dark-brownish; the other acids remained colourless. Both the marine acid and aqua regia left the undissolved earth whitish; the nitrous acid greyish; the diluted vitriolic acid brownish-yellow; the concentrated light reddish-brown; the acc- Nephritis tous, unchanged. An ounce of this substance powdered, and distilled in a retort in an open fire, yielded about a drachm and an half of phlegm, which had a penetrating empyreumatic smell, but made no change in the colour of the syrup of violets. On distilling four ounces together, there was an appearance of an actual empyreumatic oil, with a saline matter, which was found to be sal ammoniac. The matter remaining in the retort was of a reddish-brown colour. An ounce of the powdered stone, mixed with an equal quantity of fixed alkaline salt, and urged with a strong fire, did not melt, but formed a quite porous mass, in colour inclining to reddish-grey, and weighing two drachms less than the mixture did at first. Dr Lewis tells us, that the nephritic stone is a species of the indurated clays, called, from their unctuousity, flextite. With these it agrees, not only in its obvious proprieties, but likewise in its burning hard, the peculiar characteristic of argillaceous earths. Its green colour seems to proceed from copper. Pott relates, that on fusion with an equal quantity of borax, it yielded a beautiful red mass resembling an agate, with a grain of copper at the bottom. The nephritic stone is considerably the hardest of all the substances of this class.