1. This paper describes the macroscopic and microscopic changes that are seen in posterior intervertebral joints after anterior vertebral fusion.

2. We now have a reasonably clear view of the types of change seen under these circumstances. The type varies from case to case and in different parts of the same specimen. So far we have no clear idea of the sequence or the pattern that leads from the normal to complete fibrosis or osseous ankylosis.

3. Further experimental work is needed in order to build up a clear concept of the sequence of events and of their relative importance. To do this it will be necessary to immobilise joints for longer than before.

1. Six cases of quadriceps contracture in children are described. All were either premature or suffered severe illnesses soon after birth.

2. Some additional information is given about cases of the same condition previously published by other authors.

3. It is suggested that injections and infusions given to newborn babies are sometimes the cause of the condition.

4. Some of the therapeutic substances and measures which may be responsible are discussed. These include antibiotics, vitamin K preparations and "subcutaneous" fluid therapy.