Ott, J. N. 1974. The importance of laboratory lighting as an experimental variable. In: Environmental Variables in Animal Experimentation . Magalhaes, H. (ed), 39-57. Bucknell University, Lewisburg, PA.

The importance of light and illumination as extraneous variable is discussed. My suggestion is that the cage conditions are too crowded in our present racks, and there should be the same lighting for all cages in the bottom shelf as well as the top shelf. Then you won't have to rotate them, because they should be subjected to the same light, I believe, throughout all of the experiments.