Effects of sunlight on the malignancy of a transplanted tumor of the rabbit.

Abstract

Since the tumor upon which this report is based was first transplanted in the spring of 1921, 1 we have been engaged in a study of the problem of animal resistance as related to the growth and malignancy of the tumor with especial reference to factors of constitutional resistance and conditions that might cause an increase or decrease in animal resistance.

Several reports have been published dealing with some of the results of this series of investigations. 2 Among other things, it has been noted that although a good primary growth can be obtained in practically all rabbits by intratesticular inoculation, the ultimate malignancy of the tumor is subject to wide variations and that, from the beginning, there has been a striking tendency to the occurrence of periods of excessive malignancy during the spring and fall of each year. This focused our attention on the possible influence of meteorological conditions and led to a study of phenomena of resistance and of tumor growth from the point of view of meteorological influences. The results of these investigations contain many points of interest, but the present report will be limited to a consideration of sunlight.

The method employed involved the inoculation of a group of 5 to 10 rabbits each month. Inoculations were made by injecting 0.2 to 0.3 cc. of a cell emulsion into one testicle. The animals were then kept under observation for a period of two months, at which time the surviving animals were killed. Records were kept covering the clinical course of the disease and all animals were subjected to a careful postmortem examination which included the weighing of organs, noting the number and distribution of metastases, and the extent and condition of the growth in all parts of the body. The data thus obtained were reduced to a form that would permit of a quantitative expression.