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Sagittal section of vertebral canal to show the lower end of the medulla spinalis and the filum terminale. Li, Lv. First and fifth lumbar vertebræ. Sii. Second sacral vertebra. 1. Dura mater. 2. Lower part of tube of dura mater. 3. Lower extremity of medulla spinalis. 4. Intradural, and 5, Extradural portions of filum terminale. 6. Attachment of filum terminale to first segment of coccyx. (Testut.)