Where the absorption of the thinner parts of the secretion takes place too hastily in the kidnies, the hardened mucus, and consequent calculous concretions, sometimes totally stop up the tubuli uriniferi; and no urine is secreted. Of this many die, who have drank much vinous spirit, and some of them recover by voiding a quantity of white mucus, like chalk and water; and others by voiding a great quantity of sand, or small calculi. This hardened mucus frequently becomes the nucleus of a stone in the bladder. The salts of the urine, called microcosmic salt, are often mistaken for gravel, but are distinguishable both by their angles of crystallization, their adhesion to the sides or bottom of the pot, and by their not being formed till the urine cools. Whereas the particles of gravel are generally without angles, and always drop to the bottom of the vessel, immediately as the water is voided.
Though the proximate cause of the formation of the calculous concretions of the kidneys, and of chalk-stones in the gout, and of the insoluble concretions of coagulable lymph, which are found on membranes, which have been inflamed in peripneumony, or rheumatism, consists in the too great action of the absorbent vessels of those parts; yet the remote cause in these cases is probably owing to the inflammation of the membranes; which at that time are believed to secrete a material more liable to coagulate or concrete, than they would otherwise produce by increased action alone without the production of new vessels, which constitutes inflammation. As defined in Class II. 1. 2.
The fluids secreted from the mucous membranes of animals are of various kinds and consistencies. Hair, silk, scales, horns, fingernails, are owing to natural processes. Gall-stones, stones found in the intestines of horses, scurf of the skin in leprosy, stones of the kidnies and bladder, the callus from the inflamed periosteum, which unites broken bones, the calcareous cement, which repairs the injured shells of snails, the calcareous crust on the eggs of birds, the annually renewed shells of crabs, are all instances of productions from mucous membranes, afterwards indurated by absorption of their thinner parts.