The development of cholinergic ganglia in the chick embryo heart.

Cholinesterase activity was investigated in the heart of the developing chick from the 6th to 20th day of incubation. The earliest cholinesterase-positive nerve cells and fibers could be demonstrated between the 7th and 9th day. On the 13th day the nervous structure attained full development comparable with that seen in the hatched chicken. The number of ganglia increases up to the 15th day, and remains constant thereafter. The right ventricle is associated with the largest number of ganglia.