Skeletal abnormalities in chick embryos paralysed with decamethonium

Abstract

Chick embryos which had been paralysed for several days, commencing at an incubation age of 6 days, exhibited a bent, rigid neck and a distorted trunk. Examination of the skeleton in alizarin clearances revealed a number of frequently occurring bony anomalies, including fusions and asym- metries of cervical vertebrae, abnormal curvatures or rotations of the vertebral column, abnormally bent scapulae, and a bowing of the distal end of the tibiotarsus. The overall appearance of the paralysed embryos suggested that they had been affected by mechanical pressures related to growth within the confined space of the amniotic cavity. It is concluded that an important role of muscular activity during development is to counteract mechanical forces that would otherwise deform the embryo.