One approach to this question is to look at the microscopic structure of bone. In many cold-blooded animals, bone grows in dense, concentric rings. In warm-blooded animals, a complex system of closely spaced cavities, called the Haversian system, permeates the bone. By cutting bones of extinct, non-avian dinosaurs into thin slices and examining them under the microscope, we can look for these characteristics. In most non-avian dinosaurs, the microstructure of the bone looks more like that of warm-blooded animals, but the evidence is not conclusive.