Diets containing Lathyrus odoratus seeds fed to rats produce a hitherto unrecognized lesion in the epiphyseal plates. These are very wide, the cartilage matrix appears to lose cohesion, and the cartilage cells are grouped in clusters. The same diets produce loosening and detachments of the tendinous and ligamentous insertions.

Because of these two lesions, occurring independently or together, the following skeletal conditions developed in the experimental animals: Epiphyseal slippings, metaphyseal fibrous defects, kyphoscoliosis, thoracic deformities, detachments of the tibial tuberosity, subluxations and dislocations of the shoulder, diastasis of the sacro-iliac joints, degeneration of the intervertebral discs, disc herniations, Legg-Perthes-like disease of the femoral head, and valgus of the forepaws.

In practically all the experimental rats there were extensive areas of periosteal newbone formation following detachment of the periosteum.

Degenerative arthritis was observed in rats fed the experimental diets for several months. Two lesions developed concomitantly,—degeneration of the joint cartilage and loosening of the capsular and ligamentous insertions.

Bone lesions resembling those seen in Paget's disease were observed in small groups of older rats.

Dissecting aneurysms of the aorta and abdominal and inguinal herniae were observed in many rats. The collagen fibers appeared to be normal on electron-microscope examination.

It is surmised that all these lesions are due to defective formation or excessive destruction of the chondroitin sulphate of the ground substance.

The possible relationship between these lesions in rats and similar lesions in humans is a matter for further study.