A method of qualitative analysis of microscopic biological specimens is disclosed in which the specimens are rendered magnetically responsive by immunosspecific binding with feuromagnetic colloid. The specimens are placed in a vessel having a feuromagnetic capture structure supported on a transparent wall. The vessel is then placed in a magnetic field for inducing a high gradient region in the vicinity of the capture structure and, in particular, adjacent to the capture structure along the direction of the applied field. The magnetically responsive specimens are collected and immobilized by the high gradient along the wall adjacent to the capture structure for unobstructed microscopic observation. Subpapulations of distinct types of cells can thus be observed and differentiated. As transport force, such as gravity or an externally applied magnetic gradient, may be applied to the vessel to move the specimens into the high gradient region.