In these experiments changes were produced of a regenerative nature in the spines, and of a degenerative nature in the knee joints of dogs. The changes in the spine were cartilage proliferation and new bone formation. In each of three dogs the changes took place in the intervertebral spaces and in the fibrosus annulus intervertebralis. Islands of cartilage cells were seen in the bodies at their peripheries and below the intervertebral discs. In the spine of one dog there was a proliferation of cartilage into the body of the third lumbar vertebra and formation of osteoid tissue. In one dog masses of new bone were found on the anterior surfaces of five lumbar and one thoracic vertebrae. In this dog young osteoid tissue and new bone were present in the body and extended beyond the anterior surface. The changes were more pronounced in the lumbar vertebrae and corresponded to the region of the ligated veins.

Microscopically there was shown a proliferation of cartilage cells, and these cells were distributed irregularly through the bone trabeculae. Osteoblasts were present on the borders of the osteoid tissue, and in other regions nests of osteoclasts were evident. The marrow spaces contained fat, and the hemapoietic tissue was decreased in amount. In other regions the trabeculae appeared to be normal with some increase of the intercellular elements.

The dogs of this series were all kept alive for practically the same length of time,—that is, two years; so that the bone changes were of the same duration. Dog 6 and Dog 8 were the only animals kept alive for a shorter period,—i.e., two to six months; so that in these dogs were not seen the advanced processes present in the others. One may deduce from these experiments that proliferation, or rather new bone formation, resulted from venous stasis. The control animals showed no such changes.