An account of the chemical cytology of various iiormal cells of tlie licmopoietic tissues and circulating blood was published recently by Wislocki and Derripscy ( '46). The cells were explored by a variety of histoclicmical methods most of wliich had been little used before in the study of blood. Since completing the previous report, occasion has arisen to repeat and extend some of our work with tlie result that we a r e now presenting some new information and offering several minor revisions of the previous findings. These further oservations concern mainly the cytology of megakaryocytes, blood platelets, tissue eosinopliiles and mast cells.
MATERIAL AND METHODS
We have reinvestigated the basopliilic cytoplasmic staining of marrow cells. Blocks of bone marrow of several young rhesus monkeys and 6 guinea pigs were fixed in Zenker's fluid, and the deparaffinized sections were stained with eosin and methylcne blue or with metliylene blue alone. F o r purposes of ascertaining the presence or absence of ribonucleic acid in l'l'Iiis work was done in part under a grant from the Anirriran Cancer Society on the recommend:ition of the Coninlittee 011 Growtli of the N:rtionnl Rrsenrcli Council.
'Fellow of the Coitimonwcalth Fund.