(From the Arabic muk,) myxa; myxara; myxas; the viscid fluid which covers the surfaces of all the membranes, exposed to any extraneous matter, as the skin, internal membrane of the mouth, nose, lungs, oesophagus, stomach, intestines, urinary passages, & c. It is thin at its first secretion, but more viscid apparently from its union with oxygen, colourless, insipid, inodorous, and incapable of stimulating; but if its secretion is suddenly increased, it becomes a watery acrimonious fluid of a whitish or a greenish yellow colour, sometimes acquiring a smell, and occasionally the appearance of pus. In its natural state it contains some common salt and phosphat of soda, inviscated in albumen. From Dr. C. Darwin's Experiments, which Dr. Darwin himself has since claimed, it appears that, if any suspected matter be in separate equal portions, dissolved in vitriolic acid and caustic alkaline lixivium, water will precipitate any pus which exists. Pure pus will not dissolve in a dilute alkaline solution. But an experienced eye requires no such assistance.