The effect of retarded growth upon the length of life span and upon the ultimate body size. 1935.

mary in the nature of a progress report dealing with a study employing rats to determine the effect of retarding growth upon the total length of life. The present summary represents a complete, final report of this experiment employing white rats and covering a period of nearly 4 years. The object of this study was to determine the effect of retarding growth upon the total length of life and to measure the effects of retarded growth upon the ultimate size of the animal's body. In the present study, growth was retarded by limiting the calories. The growth of an animal can be retarded either by disease or by various nutritional deficiencies. Every laboratory that performs vitamin assays is familiar with the retarded growth and prompt death that result when there is a deficiency of a certain factor such as vitamin A. In such experiments the animal grows little and dies prematurely. However, a border line level of such an essential as vitamin A may permit a very slow growth and permit the animal to approach or attain