0.05) between the Zhuang and Han races.3. The sagittal diameter and shape of the spinal canal were not consistent with the external feature of the cord at C_3—C_6 vertebral levels where the sagittal diameter became physiologically reduced and at C_4 (12.92mm) it was the narrowest.4. Forms of the spinal canal (except C_1) were divided into four different types: a) circular, b) triangular, c) transitional and d) scalene.The shape of the spinal canal at C 1,2 the circular and it changed gradually from a semicircular to a triangular type at C_6 (81.31%). The triangular type then assumed the shape of a clam and polygon and become the circular type at T_6 (84.76%). The circular type became triangular again and assumed the shape of a clam at L_5 (99%). The triangular shape tended to assume the shape of a trefoil and then a bell from L_3 to L_5. The percentage of the trefoil shape of the lumbar vertebral canal was 5.02%.The results of the present study support the views of Eisenstein: i. e. the trefoil configuration is a common non-pathological condition, and is not necessarily dependent on, or related to, increasing age, osteophytosis or spinal stenosis. It is probably a developmental variation of normal anatomy.