Reinhardt, V., Reinhardt, A. 2001. Legal space requirement stipulations for animals in the laboratory: Are they adequate? Journal of Applied Animal Welfare Science 4(2), 143-149.

Animals in the laboratory need the legally required "empty space" to meet their basic spatial requirements for postural adjustment, but they also deserve functional structured space for species-typical locomotor behavior and dynamic interaction with their physical environment. Primary enclosures of these animals traditionally are unfurnished, and there is no reason to believe that the biomedical research industry will change the status quo on its own accord. Rather than counting on the professional judgment of attending veterinarians, investigators and facility administrators, The U.S. Department of Agriculture should explicitly require primary enclosures of laboratory animals to provide not only a specific volume of space, but also species-appropriate space structured for optimal use by the confined subject.