Weihe, W. H. 1976. The effect of light on animals. Laboratory Animal Handbooks 7, 63-76.

In mammals light ... serves the function of vision, regulation of optokinetic reflexes, and regulation of neuro-endocrine functions and behaviour. ... The illumination conditions existing around the animals in their cages need to be considered for each species and for a much wider range of functions than has previously been thought necessary.