Orientational distribution of collagen fibers in cobra skin

The orientation and distribution of collagen fibers were studied in leather prepared from cobra skin using both the mechanical method and Osaki's microwave method. The degree of preferred collagen-fiber orientation was largest at the centre of the dorsum and decreased gradually from the dorsum to the abdomen. The collagen fibers were, on average, aligned parallel to the spinal column in the dorsum, and tended to be aligned equally in all directions in the abdomen. The skin expanded easily in the direction perpendicular to the direction of collagen-fiber orientation. These results indicate that it is difficult for the skin to expand or shrink in the cranial to caudal direction, whereas it is relatively easy for the skin to expand around the circumference of the body of the cobra. Collagen-fiber orientation therefore seems to be closely related to the functional motions of cobra skin during locomotion and when swallowing prey.