1 . Young Wistar rats fed on a diet containing 0·3 per cent semicarbazide hydrochloride developed the characteristic lesions of osteolathyrism. This consisted of kyphoscoliosis, displacement of epiphyses and dislocations of joints. A pathological study of the skeletal lesions showed widening, disorganisation and tears of the epiphysial plate with the zone of maturing cartilage showing the greatest increase in width. The severe kyphoscoliosis was due to a derangement and displacement at and through the epiphysial plates of the twelfth thoracic or first lumbar vertebra.

2. Some of the compounds that are known to produce osteolathyrism in laboratory animals are beta aminopropionitrile, amino acetonitrile, mercaptoethylamine and semicarbazide. The mode of action of the lathyrogenic compounds was analysed in the light of a number of experiments done in this laboratory.

3. lt is possible that they interfere with the metabolism of the epiphysial plate. There appears to be a decreased polymerisation of the ground substance of the epiphysial cartilage, but the exact metabolic reaction involved is not known. Other chemicals of similar structure, with the same reactive groups, did not show lathyrogenic properties. It is concluded that it is not a particular chemical structure, configuration or specific reactive group that is responsible for the production of osteolathyrism. The chemistry of the lesions still remains to be solved.