THAT serous fluids from patients suspected of having malignant tumors may yield information of considerable diagnostic value has been established for many years, and in 1917 Mandelbaum1 devised a technic for the preparation of cell blocks that, with but few modifications, is generally employed at present. Evaluations of the procedure as employed in various laboratories have been published by a number of workers, including Zemansky,2 Schlesinger3 and Honigman,4 all of whom showed conclusively that, when properly carried out, the method is not only technically practical but also diagnostically useful. Zemansky has traced in some detail the development of the method, . . .