Growth characteristics of free tumor cells transferred serially in the peritoneal fluid of the mouse.

poorly if at all in strains other than dba (@1@).In strain dba (@1@)it grows steadily as a localized tumor with almost no regression. It was found in preliminary experiments to elicit a relatively mild leukocytic reaction. The mice used in quantitative experiments with 5-37 were all males of the Car worth Farms W Strain (CFW), but dba, Swiss, and CSH mice also were found convenient in pre liminary studies. Male dba (@1@)mice were used in the work with malignant lymphoma. Subcutaneous implants 6 or 7 days old were ground in a tissue press and suspended in a con venient volume of 0.85 per cent NaC1 solution. Be fore inoculation of the requisite number of tumor mash cells, the number of viable cells in 0.1 cc. of the mash suspension was determined. The sus pension was separated from tissue fragments and cell clumps by sedimentation and decantation. A sample of suspension was placed in a hemocytome ter previously coated with a 0.0@ per cent alco holic solution of neutral red. Five minutes later a count was made to compute the number of viable tumor cells per 0.1 cubic centimeter. Cells with nuclei showing any trace of neutral red stain were considered dead. This count indicated the amount of dilution necessary to obtain the requisite num ber of viable tumor cells per cubic centimeter. Tumor cell counts in the peritoneal exudate were made in the same way, except that the total num ber of viable tumor cells in 0.1 cubic centimeter of original exudate diluted 1:10 or 1 :@0 was com puted by combined methods of total cell counts in the hemocytometer and differential tumor cell counts in stained smears. One smear was stained with Wright's stain and the other by the aceto orcein method. The results of counts in both