Cardiac innnervation in the prenatal stages of Anas poecilorhyncha.

Innervation of the heart has been observed in the progressive developmental stages of Anas poecilorhyncha ranging from 8 h to 14 days stages using silver impregnation technique of Ungewitter (1951). Vagal cardiac fibres reach the atrial wall on the fourth day. Migration of nerve cells and ganglia has been observed from the more anterior regions to the heart along the precaval veins. The adult pattern of the heart is first established at the 8 days stage while the traces of the endocardial cushions are still present. The atrioventricular valves show rich innervation. The subepicardial ganglia and simple myocardial plexuses appear in the 8 days stage and become well differentiated on the 10th day. The subendocardial plexuses are reported to be sensory for the testing of the properties of the blood while the myocardial plexuses seem to have motor control over the working muscles of the heart specially those of the atria where rich innervation is observed. Local reflex areas have been described.