The effects of paralysis on skeletal development in the chick embryo. I. General effects.

In order to investigate further the effects of paralysis on skeletal development in the chick embryo, paralysis was induced at 6 days of incubation by dropping 0.2% solution of decamethonium bromide onto the chorioallantoic membrane and maintaining paralysis through to 20 days of incubation. General effects of paralysis included lower body weight, marked subcutaneous oedema, twisting of the neck to the right with marked rigidity, and protrusion of the lower beak beyond the upper. Skeletal abnormalities included cartilaginous and later bony fusion between cervical vertebrae and distortion of scapula and pubis. Long bones were normal in their general form but showed marked reductions in full length and in length of the calcified diaphysis. The patella occasionally underwent chondrification, unlike the tibial cartilage at the tarsus. Reduction in length of the bones of both jaws occurred but was substantially greater in the upper, resulting in the protrusion of the lower. Ossification times of most skeletal elements were little affected by paralysis but some centres appearing nearer the end of incubation showed slight delay in their times of appearance.