Chronic inflammation of the bones sometimes extends to the membranes of the spinal cord; and when the curvature is very great, the cord may be so compressed that it cannot properly discharge its functions. Suppuration may take place at different stages of the disease, sometimes earlier, sometimes later. “The soft parts in the neighborhood of the abscess become thickened and consolidated, forming a thick capsule, in which the abscess is sometimes retained for several successive years; but from which it ultimately makes its way to the surface, presenting itself in one or another situation, according to circumstances. In the advanced stages of the disease, new bone is often deposited in irregular masses on the surface of the bodies of the neighboring vertebræ; and where recovery takes place, the carious surface of the vertebræ above, coming in contact with that of the vertebræ below, they become united with each other, at first by soft substance, afterwards by bony anchylosis.” Where the bones are affected by scrofula, bony anchylosis does not so readily take place as where they retain their natural texture and hardness. Occasionally, portions of the ulcerated or carious bone lose their vitality, and having become detached, are found lying loose in the cavity of the abscess. The pressure of a large abscess on the surfaces of the contiguous vertebræ may cause an extensive caries far beyond the limits of the original disease. CHAPTER III. OF TUMORS. In giving a brief description of tumors, the following classification has been adopted from Gross, as presenting the most practical and convenient arrangement of the subject: I. _Benign or Non-Malignant Tumors._ 1. Cystic Tumors. _a._ Simple Cysts; including Serous, Mucous, Synovial, Colloid, Sanguineous, Salivary, Milk, Oil, Seminal, and Dermoid Cysts. _b._ Compound or Proliferous Cysts. 2. Hydatid Tumors. 3. Myxomatous „ 4. Lipomatous „ 5. Fibrous „ 6. Cartilaginous „ 7. Osseous „ 8. Papillary „ 9. Polypoid Tumors. 10. Myomatous „ 11. Vascular „ 12. Neuromatous „ 13. Adenoid „ 14. Lymphatic „ II. _Malignant Tumors._ 1. Sarcomatous Tumors. _a._ The Round Celled. _b._ The Spindle Celled. _c._ The Giant Celled. 2. Carcinomatous Tumors. _a._ Scirrhus Tumors. _b._ Encephaloid „ _c._ Melanotic „ _d._ Colloid Tumors. _e._ Epithelial „ I. Benign or Non-Malignant Tumors.