1Attributive and (now rarely) in the genitive. Designating a method of fixing and staining nerve tissue to identify degenerating myelin, which is selectively stained black; especially in "Marchi method", "Marchi technique". Also: designating the combination of reagents (a solution of potassium bichromate and osmium tetroxide) employed in this method.

2Attributive Employing, or resulting from the use of, the Marchi method.