As seen in the human subject spinal caries is usually tubercular and is known as “_Pott’s disease_.” As seen in old horses it appears to be rather a result of other infections, especially purulent, and may have started in connection with traumatic or mechanical injuries to the bones and ligaments. In such cases I have seen it repeatedly in hollow backed horses in which the line of the spine descended abruptly and extremely from the withers and rose again to the sacrum. The distortion was so great that the back appeared as if it could barely sustain the weight of the animal and yet the patients were kept at work and proved useful for light driving. Post mortem examination showed extensive caries and suppuration of the vertebral bodies, confined, however, to one or two segments as if due to a mechanical lesion. In the region of the loins it is much more likely to affect the articulations of the vertebral rings, because of the manner in which these are wedged into each other when the spine is pressed downward. In the neck where the normal movement is so much freer such injuries are much less common. Caries affecting the articular surfaces of the axoido—atloid joint is by no means uncommon. It may follow poll evil, or injuries sustained when a horse runs against a wall, or in the fights of bulls or rams. Disease of the vertebræ may be of the nature of rachitis occurring in this case in early life. In cattle the disease is liable to be tubercular in which case, not only is the bone invaded but the morbid process extends to the intervertebral cartilage and projecting, presses on the spinal meninges and cord. It may even encircle the entire spinal cavity and strangle the cord. If the pus should extend downward it may form abscess under the spine, and rupture into an internal cavity or externally.