Twenty-two patients with cysts of the lateral meniscus have been treated by operation. A modified operative procedure is described whereby the meniscus is inspected for a concomitant tear. A tear of the meniscus was found in ten patients and these were treated by meniscectomy. The remaining twelve cases were treated by excision of the cyst only. The rehabilitation period was considerably less in these patients. Recurrence of the cyst did not occur. The rationale for local excision is based on the similarity between the cyst of a meniscus and a simple ganglion, and also on the desirability of preserving the meniscus.

1. Cases are presented to show that blackthorn inflammation is not uncommon in the West Midlands.

2. The pathology is that of a chronic non-suppurative inflammation.

3. Cases are divisible into three groups on the basis of their history. In the third group, with no history of blackthorn trauma, diagnosis may be very difficult.

4. Removal of the blackthorn fragments causes prompt resolution of the inflammation.

Puppies in the second half of their growing period have been observed for one and a half to four and a half months after creation of a superficial femoral arteriovenous fistula on the right side. From measurements of the whole bone and from microradiographic and tetracycline-fluorophore studies of the diaphysial bone, it is believed that the following statistically significant phenomena may be attributed to the influence of the arteriovenous fistula.

1. All bones distal to the fistula are influenced in their growth. The tibia and metatarsals become heavier and larger, but retain normal shape. Although stimulation of longitudinal growth is small, it is significant for the tibiae and nearly significant for the femora in these short-term experiments.

2. The histological structure of the bones remains normal but quantitative changes are induced. The compact bone is more porous because of an increased number of osteones. Haversian turnover itself is affected in that the individual formation time of osteones tends to become longer, especially in the metatarsals.

3. Periosteal new bone formation is immediately stimulated, producing a flare of new bone. This accounts for the increase in diaphysial weight in the tibia but not in the metatarsals, where the same effect results from decreased resorption of old bone.

4. Endosteal new bone formation is depressed, especially in the metatarsals, resulting in an enlarged medullary cavity.

1. The appearance of decalcified bone matrix in the electron microscope is described.

2. In the matrix two types of collagen fibril have been distinguished. Differences observed are in solubility, x-ray diffraction pattern and appearance. In infant bone the form which appears as fine fibrils predominates. In adult bone the form which appears as tubular fibrils of larger diameter predominates.

3. In bones from elderly subjects the chemical reaction employed to convert collagen into eucollagen sometimes hydrolyses fatty acid esters, and lines due to the free fatty acid are found on the x-ray diffraction patterns of the insoluble residue after citrate extraction.

4. In ancient bones and fossils the stable tubular form of collagen survives, but not the fine fibrils.

5. When decalcified, the matrix in osteoporotic bones loses its architecture and fibrillar form. Under conditions in which only a small fraction is dissolved from normal bone most of the collagen in osteoporotic bone disperses in citric acid. The insoluble residue then gives a modified x-ray diffraction pattern.

6. Evidence has been produced to suggest that the immediate cause of many forms of osteoporosis is some local factor affecting the osteocytes, rather than a general chemical effect.

1. A study of 2,200 patients receiving electro-convulsive therapy showed that fifty-three sustained fractures or dislocations—an incidence of 2·4 per cent. Of the fifty-three injuries, twenty-one occurred in the spine, fifteen in the neck of femur, fifteen in the upper end of humerus, one in the coracoid process; one dislocated jaw required anaesthesia for its reduction (other cases of transient dislocation of the jaw are excluded).

2. The incidence, site, and type of spinal fractures are recorded, and the relation of the fracture to the first convulsion is noted. No late changes were found in the spines of patients examined two years or more after treatment. A neutral position of the spine during the convulsion is believed to diminish the risk of fracture.

3. Fracture of the neck of the femur is a serious injury in these patients. In one case the injury was bilateral.

4. The fifteen cases of fracture-dislocation of the upper humerus are analysed. They included two cases of posterior dislocation of the humeral head; the possible mechanism of this is explained and a method of prevention suggested.

5. Fifty-three patients with chronic epilepsy with psychosis were examined. Four cases of fractured spine were discovered. The site of fracture was different from that of fractures caused by convulsive therapy and a reason for this is suggested. The type and mechanism of the fracture are similar in the two groups.