THIN PREPARATIONS OF HEMOPOIETIC TISSUES

Previous papers dealing with behaviors and activities of blood cell nuclei have been recording mainly results with the imprint method and observations of blood cells cultured in vitro. The present paper demonstrates that the Feulgen "gentle squash" method as well as digestion with N HCl followed by toluidine blue staining at pH 4 reveals the same nuclear behaviors as the imprint method. Imprinting on millipore filters with subsequent fixation in Zenker's acetic solution followed by the Feulgen or toluidine blue staining method (the latter with or without previous N HCl digestion) is reported for the first time. The millipore imprint preserves a thicker layer of cells than imprinting on glass slides. Also cell stages which may not easily stick to glass seem to adhere well to the millipore filter. The filter imprint may in places present as many cell layers as a thin slice cut on the microtome, but without the disadvantage of having large or elongated cell stages cut into pieces by the microtome knife.