| macerate | To soften by steeping or soaking. Origin: see maceration (05 Mar 2000) |
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| maceration | The softening of a solid by soaking. <pathology> The softening of a tissue by soaking, especially in acids, until the connective tissue fibres are so dissolved that the tissue components can be teased apart. In obstetrics, the degenerative changes with discolouration and softening of tissues and eventual disintegration, of a foetus retained in the uterus after its death. Origin: L. Maceratio (18 Nov 1997) |
| Macewen's sign | <clinical sign> Percussion of the skull gives a cracked-pot sound in cases of hydrocephalus. Synonym: Macewen's symptom. (05 Mar 2000) |
| Macewen's symptom | <clinical sign> Percussion of the skull gives a cracked-pot sound in cases of hydrocephalus. Synonym: Macewen's symptom. (05 Mar 2000) |
| Macewen's triangle | A triangle formed by the root of the zygomatic arch, the posterior wall of the bony external acoustic meatus, and an imaginary line connecting the extremities of the first two lines; used as a guide in mastoid operations. Synonym: Macewen's triangle. (05 Mar 2000) |
| Macewen, Sir William | <person> Scottish surgeon, 1848-1924. See: Macewen's sign, Macewen's symptom, Macewen's triangle. (05 Mar 2000) |
| Mach effect | The appearance of a light or dark line on a radiograph where there is a concave or convex interface in the subject, a physiological optical form of edge enhancement. See: Mach's band. (05 Mar 2000) |
| Mach line | The apparent line of contrasting density bordering a soft tissue shadow on a radiograph; it is an optical illusion constructed by the observer's retina. (05 Mar 2000) |
| Mach number | A number representing the ratio between the speed of an object moving through a fluid medium, such as air, and the speed of sound in the same medium. (05 Mar 2000) |
| Mach Zehnder system | Interferometric system in which the original light beam is divided by a semi transparent mirror: object and reference beams pass through separate optical systems and are recombined by a second semi transparent mirror. Interference fringes are displaced if the optical path difference for the reference beam is greater and this can be compensated with a wedge shaped auxiliary object. The position of the wedge allows the phase retardation of the object to be measured. The Mach Zehnder system was used in a microscope designed by Leitz. (18 Nov 1997) |
| Mach's band | A relatively bright or dark band perceived in a zone where the luminance increases or decreases rapidly. (05 Mar 2000) |
| Mach, Ernst | <person> Austrian scientist, 1838-1916. See: Mach's band, Mach number. (05 Mar 2000) |
| mach-zender interferometer | <radiobiology> This is a variation of the Michelson interferometer which is used mainly in measuring the spatial variation in the refractive index of a gas (or plasma). A Mach-Zender interferometer uses two semi-transparent mirrors and two fully reflective mirrors located at the corners of a rectangle. The incoming beam is split in two at the first semi-transparent mirror, and the two halves of the beam travel along separate paths around the edge of the rectangle, meeting at the opposite corner. Typically one beam is a control, and the other travels through the system under study. The two beams meet at the second semi-transparent mirror, after which they are mixed together and interfere. (09 Oct 1997) |
| Machado-Guerreiro test | A complement-fixation test for infection with Trypanosoma cruzi. (05 Mar 2000) |
| Machado-Joseph | A rare form of hereditary ataxia, characterised by onset in early adult life of progressive, spinocerebellar and extrapyramidal disease with external ophthalmoplegia, rigidity dystonia symptoms, and, often, peripheral amyotrophy; found predominantly in people of Azorean ancestry; autosomal dominant inheritance. Synonym: Azorean disease, Portuguese-Azorean disease. Origin: Surnames of two families studied in major descriptions of the disease. (05 Mar 2000) |