Just as in normal tissues, it has been found that growth and development of a malignant neoplasm are influenced by temperature both quantitatively and qualitatively. The most striking effect was the acceleration in the rate of growth of the tumor at higher temperature, and retardation at lower. The ultimate size attained within periods averaging 3 months was regularly much greater at higher temperature.

Also, the character of growth was quite different. At high temperature, there was more efficient vascularization, and the tumors formed long, branching, tubular outgrowths and cysts; at low temperature the outgrowths were short and stubby and cysts were rare.

These differences were accentuated by repeatedly passing the tumor from one generation to another. In particular, in such serial passages, there was a remarkable tendency for the tumor to develop greatly dilated tubules and large cysts, which later, however, became solid as the result of ingrowth from the wall.

The experiments demonstrate that the carcinoma in the frog can exist over a wide range of temperature. Even a temperature as low as 4°, as in the hibernation experiment, produces no injury to the tumor. This result is consistent with the common occurrence of large, healthy, spontaneous tumors in frogs which have recently hibernated in their natural state.