An experimental study of necrosis in tumors.

Factors that regulate the amount of viable tumor an animal can support have been studied in rats bearing Walker carcinoma 256. There is a maximum amount of viabletumor an animal can support, but continued growth of tumor resulting in increase in the amount of necrotic tumor occurs until death of a rat bearing Walker carcinoma 256. The number and location of tumors in an animal do not significantly influence the per centage of the total amount of tumor tissue that is necrotic except in instances in which tumors are very small. In rats with Walker carcinoma 256 there is a positive relation ship between the percentage of the total amount of tumor tissue that is necrotic and the percentage of host weight occupied by tumor. Extensive necrosis occurred in Walker 256 tumors in rats placed under a barometric pressure of 8 inches of mercury for 5 hours. There is rapid growth of tumor that remains viable if the tumor-host equilibrium is disturbed by decreasing the amount of viabletumor by placing a tumor-bearing rat under reduced barometric pressure.